michaelmoore

There may be some misunderstanding. I'm not talking about the traditional English riding armor Just the usual lightweight and not at all encumbering modern plastic stuff: All the modern helmets (other than those silly chopper things which I have difficulty classing as helmets) I've seen have padding completely around the ear whether they are open face or full face, so I'm having difficulty seeing how adding the chin bar is going to restrict my hearing. I've never noticed any problem hearing the observer telling me to come ahead into a section, much less being able to detect the engine/exhaust noise. I just went down into the back of my garage (closed door) put my helmet on, and was able to hear tire noise from the cars going by on the street 75 feet away. I try not to make a habit of letting loose of the bars and waving my hands over my head while in a section and that's about the only time I can think of where the armor restricts my movements. I'f I'm standing and holding the bars as in the photo above (taken at Sears Point at an AHRMA National about 5 years ago) I can't claim to be aware that I'm wearing the upper body armor. It is certainly no more restrictive than the Belstaff or Barbour jackets I've worn, and I think I've seen people pictured wearing those in sections. I occasionally see other people falling off (even in our not terribly challenging vintage novice lines sometimes fall) so I'm pretty sure that I'm not the only person who ever parts company with their bike, even in relatively easy sections. Maybe Toni Bou needs to have a complete lack of restriction and the ability to hear crickets chirping from 30 paces away when he's riding. He can probably get away with riding trials wearing nothing more than his boots, though if anyone could benefit from some protective gear if they should fall those world class guys look like they could. I don't normally plan my falls or have much control over which portions of my anatomy are going to be impacting specific features of the section (or the bike). In the white-hot heat of competition for 3rd place Novice riding gear doesn't seem to be a major factor. Other, of course, than picking myself up and thinking "wow, I'm sure sore, and I've still got two more loops to ride." Ziippy, maybe you know people like that. It wouldn't surprise me that there are people who think that way. But I hang out with the novice riders (which usually seems to be a pretty well subscribed class) and we tend to not have too much ego involved as all we have to do is look at the people riding the 2 line (much less anything harder than that) and then look at our route cards to see that we've got 20 or more points from the easy sections. I suspect that there's a relationship between skill level and falling off in a section, and that the lower the skill level is the easier it is to fall off, even on easier obstacles. I think novice trials riders, even those who don't try stuff significantly beyond their skill level, are probably going to be finding benefit in a higher level of protective gear. But if someone else wants to ride in a bobble cap and t-shirt that's their call. I remember riders at club trials back in the 70s who liked to dress like that, and there was one instance when a person was looking pretty dazed and bloody after a crash and it was 10-15 minutes before it was safe for him to get back on his bike to ride to the pit area. Their lack of protective gear doesn't affect me, and my extra pound or two of plastic armor is unlikely to have much of an effect on them. cheers, Michael

I was watching some of the world round videos on Youtube today. I'd not seen any modern trials at that level before and "impressive" doesn't begin to describe the riding ability of those guys. However, I thought minders were supposed to be there to catch someone before they fell off something and injured themselves. It looked like trials has become a team sport, with the minder right next to the rider in a section, and it seemed like he was busy giving instructions to the rider on wheel placement and lines. This seems very odd to me. I could see getting advice from someone before riding a section. I'm certainly glad to get good advice on lines and technique. But when did the minders start doing this detailed "in section" management? Do the rules have provisions that cover behavior of the minders while a section is being ridden so that a rider can be penalized if the minder does something he shouldn't? Is a minder limited to a specific number of times he can offer advice/coaching, or can they give direction for every foot of the section? Do the riders normally wait for the minders to catch up before they try each obstacle? You'd have to be really fit to spend that much time doing rough terrain running trying to keep up with the rider. cheers, Michael

I haven't done a trials bike yet. I've built or modified several RR frames and a couple of vintage scramblers. I think I mentioned above that on the trials frame I'll probably just use 26/27 degrees as that should work OK with the KT250 or Bultaco fork sets I've got on hand. Modern rake angles wouldn't look period and if I'm going to ride a vintage bike I want it to look period.. On my KT250 I'm not concerned particularly about turning it into a worldbeater and I may just jig off the stock frame for steering head/swing arm pivot/damper mount positions. Mostly it is that the way they built the stock frame and swing arm annoys me every time I look at it. I can't imagine why they built it like that when they could have copied a Rickman, Cheney, Gollner or other frame design of the period (or evey 5-10 years earlier) instead of making it look like some late 1950s frame. cheers, Michael

FYI, a copy of the first "Twinshock" book just arrived and there is a photo of the 1967 Cheetah works team (Mick Whitlock, Chris Cullen and Arthur Dovey) with all of their bikes having front disc brakes. cheers, Michael

It isn't so much the way the power is delivered as that seems pretty controllable on my bike. I'd like more flywheel because if I'm going along dead slow at minimum RPM sometimes hitting a rock or root can be just enough extra load to cause the bike to stall. I don't want to gear the final drive down to allow more RPM or to run a high idle. I wouldn't mind having better throttle control and the ability to better pay attention to everything going on in a section so as to be able to avoid the root or give a small whiff of throttle to get past that point. Having some more flywheel mass on the KT would let it run on "autopilot" a little more when in those extremely slow speed/RPM situations. Maybe having had a lot of big thumpers (Matchless, BSA, Yamaha) has something to do with my preference for more flywheel. The 325 Sherpa T ran like my thumpers - smooth low end power and lots of flywheel. The KT has good power, it just is a bit "zingy" for my tastes. A flywheel weight (which I do intend to make) should help that. cheers, Michael

majestyman340, that's one of those "it depends" situations. Do you need a faux-replica of a modern bike in order to clean your twinshock sections or Pre65 sections? Is the steering geometry on a modern bike the determining factor, or does 40-50lbf less weight play a part? "Ideal" rake seems to steepen as the years go past. Tony Foale has done some experiments showing that you need some trail, but bikes with zero rake (this was his R75 BMW being used as a test bed) were quite rideable, and it appears that getting rake down into the 10-15 degree range can have some benefits. You can see an article about that at http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm But with a bike with a regular steering head it gets really awkward to get the steering head attached in a position to allow those steep rakes.and there are photos in the article that show how far the steering head has to move forward. Also note that Tony comments that with steeper rake the bike is less sensitive when dealing with ruts, and that may be a definite factor in steeper rakes for trials bikes. Are 2-3 degrees less rake going to make you suddenly clean every section you ride? I wouldn't expect that if I were the rider. I think that getting enough practice and skill so that we can ensure the wheels are exactly where we want them in a section, instead of just within +/- 12", is far more likely to improve our scores than changing from steering geometry that has proven to be "good enough" for many people. If you are converting some bike that originally came with 32 degrees and 5" of trail into a trials bike, then I'd think that yes, deraking it down into the 26-27 degree range is probably going to be a good move. If you are starting with something that was pretty well designed to be a trials bike you are probably going to start seeing a case of diminishing returns. What I am trying to say that if you make a change to one thing a person needs to consider all the possible ramifications and then decide if they also need to be addressed at the same time. If you change the rake you've now got a different trail number if you didn't change clamps. If you moved the front wheel around while changing rake (or changing the clamps) you now have a different wheelbase and weight distribution. Does changing just the rake and letting all the other factors end up where ever they happen to end up make things better? Beats me. Like Dirty Harry said in the movie, you've got to ask yourself "do you feel lucky?" When I build a new frame for my KT250 or my TTY400 projects I'll probably just use 26-27 degrees as the different forks I've got were all designed with offsets for that kind of rake, and I won't have to (at least at the start) have to make new triple clamps too. And for a pre 1978 class bike (AHRMA Modern Classic) the front end of the bike will look period with that kind of fork rake, where if it had 21 degrees it wouldn't. I'd find it interesting to do some experimentation to try and determine what changes do have a significant effect, and whether that effect is good or bad, and how that change interacts with other changes. Footpeg and handlebar positions seem to have noticeable effects without changing the frame around. Engine position (up/down, fore/aft) can have an effect without changing steering geometry. Mix four or five things up and who knows where you'll be, or if you'll be able to say "oh, it was obviously the steering rake change that made the bike better, and the changes to foot pegs and wheelbase and engine location had no effect." But I'd do that kind of experimentation for the fun of it, not because I expect it will make me an expert trials rider. It may be that the experimentation would lead to some conclusions like "the footpegs are better off at the leading edge of the rear tire and 12" off the ground instead of 3" behind that point and 3" higher" and I could modify my bike accordingly and make some small changes where the original designers don't seem to have gotten things right. I'd be loathe to make any blanket recommendations like "every trials bike in the world should be modified to have 22.5 degrees of rake, and you should sacrifice any other dimension needed to arrive at that rake angle." Don't forget too that different people like different things. Some people love to slide a MX bike around a course and go just as fast as someone who loves to square off every corner. Figuring out what YOU are comfortable riding and what works with YOUR riding style is important. Paioli, trial and error can definitely get you there. But knowing what counts as "error" so you can avoid trying it is likely to get you there quicker. cheers, Michael

FYI, one of the engineers on my chassis list says that the steered inertia will be a radius squared effect, and not a linear one as I laid it out. Sorry for the error. cheers, Michael

A TY175 is probably a fair bit better than a TL125. Less weight probably makes more of a difference for a newer rider than the power but you still need to have "enough". Most of the time you don't need more power. But a small bike doesn't have any reserve and if you have to roll off and roll back on in a climb you may not have enough power to recover the lost momentum. If everything in the section goes as planned then the less powerful bike is just fine. A more powerful bike might get you into trouble by giving you more power when you don't need it, or it might allow you to pull out of something instead of stopping. It is like riding a peaky first year CR125 around a motocross course and then hopping on a 400 Maico. An expert may be able to just as fast on either one (and I've seen fast guys ride a 125 in the 250 and open classes and do well on tight tracks) but a novice may have an easier time on the big bike with a broad and smooth powerband than they will trying to keep the 125 on the pipe. I like heavy flywheel bikes. I wish I could get my KT250 to have as much flywheel as my Sherpa T had. But other people like a snappier power delivery to attack a section with. I like a big soft engine with lots of flywheel that lets me idle through and put my attention on steering instead of trying to keep the engine from stalling or being in the right gear. If the trials you attend all have those "meet yourself around every turn" tight sections a TY175 or 123 Cota may be the ticket. If instead you have predominately long loose uphill climbs with entry and exit cards only and everything in between unmarked then a big bike might be "more perfect" than the little one. Horses for courses. cheers, Michael

Hi Woody, If you get the books on motorcycle chassis design and construction by (respectively) Tony Foale and John Bradley you'll find they have both done a very good job of explaining things on those subjects. I'd expect the handling to be quite different from those changes. I'll guess the Ossa had 27 degrees of rake and 85mm of ground trail (those numbers seem to be ballpark for the mid 1970s. A 21" front wheel's about 26" OD/660mm. That gives some numbers to evaluate the change. The center axle clamps would have 74mm of offset for that geometry and you'd have a real trail of 75.74mm (real trail is the actual number that does the work, you can read about that in Tony Foale's writings). If your leading axle forks had 35mm of lead (I'm figuring 35mm stanchion with 10mm thick sliders and the 15mm axle right up on the leading edge of the slider - 17.5 + 10 + 7.5 = 35 so they may have had even more than that but that looks close to the way the Bultaco forks were in a photo that is handy) your new offset is now 109mm. That gives ground trail of 45.8mm and real trail of 40.8mm. I think it should have been pretty easy to have the front end knocked off line if it hit a rock -- you'd have to hold on pretty tight as it wouldn't have as much self-centering available. If you were just riding straight ahead on fairly smooth dirt at a slow speed you might not notice that effect very much. Your small rearward change in the weight distribution might also make it a little more "nervous" in the rocks. Moving the wheel 35mm or so forward moves a big part of the steered mass forwards too. That's the issue I was discussing above. It looks to me like much of the nimbleness/quick turning on a trials bike may be more in the wheelbase than in the steering geometry. 48" wheelbase bikes will easily make a turn where a 55" wb bike doesn't stand a chance. For a given radius of bend a larger wheelbase means you've got to turn the forks more to make it. If the forks are already at the stops you are out of luck. I just looked in a copy of Tony's book and he even mentions trials bikes in the section on wheelbase "A practical consideration for trials bikes is that, for a given degree of steering lock, the minimum turning circle is smaller with a shorter wheelbase. For this reason, trials machines have wheelbases as short as 49-50 inches." Gaunt's little Jawa was reported by Morely to be 50.5", and the 123 Cota as 49.6". Your experience is why I tried to point out that you often can't change just one factor without having other things change too, and that sure muddies the waters when trying to determine what effect a change has. My previous post was addressing strictly the different placement in mass in leading axle vs center axle forks as I've seen comments over the years that the leading axle are supposed to be "better" by having a lighter feel to them and it seems to me that we're talking pretty small changes in mass locations and and normally fairly slow and smooth steering movements so you don't have a lot of momentum being built up and slowed down. To evaluate only that factor by going out and riding you need to keep wheelbase, rake, trail and overall weight distribution of the bike constant. You could have had the same experience on the Ossa by keeping the center axle forks and putting on a set of clamps with extra offset equal to the offset in the sliders of the forks you tried with the Ossa clamps. What you did was make some very significant changes in the steering geometry and wheelbase (and a little on weight distribution) and was quite a different experiment from what I'd proposed. It was interesting to hear your comments. As has been noted, you can't just cut and shut and change the steering head angle without changing the wheelbase and possibly also raising the front end from the steeper forks. One change leads to another. If you want to keep wheelbase the same while steepening the rake you need to cut off the steering head and rotate it forward (and away from the frame) around the front axle, unless you are planning on doing a cut and shut and then lengthening the swing arm to get the wheelbase back. And once you've done that you've moved the engine/footpegs closer to the front wheel and changed the weight distribution too. You've also changed the trail when you changed the rake and retained the same forks and clamps. I made my comments because it is clear that a lot of people don't have a good understanding of this (I won't claim to be an expert, but it is something that has interested me for decades) and they often tend to focus on one thing that they can see and say "there's the difference." Leading axle vs center axle is one of those "oh look, that's different, that must be it" things. But if both sets of forks put the axle through the exact same path from full bump to full rebound you've made zero change in the steering geometry. Swapping leading vs center axle fork tube assemblies around in the same clamps will make a very significant change. It is sort of like how people will say "my frame is so light because it is made from 531 or 4130" when those steel alloys have the same mass as mild steel. It isn't the type of steel that makes the frame light, it is having less of it used to make the frame. But they see a "531" sticker and figure that obvious difference has to be the reason. cheers, Michael

I bought a well-used TL125 after selling my 325 Bultaco. I found the TL had just enough power to get it into things that I couldn't get it out of, or at least not without dragging it. On the other hand, I've seen better riders on painfully stock TL125s clean things I couldn't on my KT250. The worse your skills are the more help you need from the bike, or at least it seems that way to me. cheers, Michael

FWIW, I grabbed some numbers and did some simple calculations which hopefully I haven't fouled up. Based on a modified Yamaha DT2MX front end with the lightest combination of parts (from Barry Watkin's "Lightweight Weapon" article) center axle triple clamp w/stem assy 5.75 lbf front wheel assy 18.5 lbf fork tubes complete (both) 13 lbf My KT250 clamps look to be roughly 6.875" OC for the fork tube spacing. For an easy comparison I decided to use 3" offset in the clamps for a center axle fork and 1.5" offset for a leading axle fork (with axle still at 3" offset). For the center axle fork leg the center of the tubes are on a radius of 4.563" (from the steering axis). The leading axle tubes would be 3.751". The wheel radius is 3". I decided to use 1.25" radius for the center of mass of the clamp assy with an assumption that the changes between flatter clamps/axle boss and deeper clamps/no axle boss would be a wash. offset 3.0" on forks center axle fork leg radius 4.563", mass 13lbf, mass X radius 59.319 lbf/inch triple crown radius 1.25", mass 5.75lbf, mass X radius 7.1875 lbf/inch wheel radius 3", mass 18.5lbf, mass X radius 55.5 lbf/inch sum = 122.01 lbf/inch offset 1.5" on forks leading axle fork leg radius 3.751", mass 13lbf, mass X radius 48.763 lbf/inch triple crown radius 1.25", mass 5.75lbf, mass X radius 7.1875 lbf/inch wheel radius 3", mass 18.5lbf, mass X radius 55.5 lbf/inch sum = 111.45 lbf/inch The leading axle forks end up about 91% of the total of the center axle fork. An interesting thing about actually doing some numbers is seeing that I forgot that the fork tube assys would end up on a longer radius than the wheel assy which magnifies the effect of moving them around. If you put a 2.75 lbf rod onto one of the leading axle fork tubes so that it is on the same 3.751" radius you'd have pretty much the same steered mass number as the center axle fork assy. Still, the difference is not a very large percentage. If you are riding in loose dirt/sand/mud I wonder how much that might serve to damp out that small difference enough to make even the aces not be able to reliably notice it? And if your handlebars were an inch or two wider or narrower between the types of forks you might offset the difference and have them feel the same. Would I notice it? I don't know. I might be able to concentrate on noticing the difference during an experiment (especially on a frictionless surface so I was only noticing the fork mass effects and not the tire squidging about) and detect something, maybe not. In a section it might depend on how much I was having to concentrate on not going out of bounds. cheers, Michael

Hi Woody, The axle doesn't know if it is in front, behind or dead below the fork tube. All leading axle forks do if the axle position and path during the suspension movement are held constant is to slightly reduce the polar moment of inertia of the steered mass. And since the wheel is the biggest part of that and doesn't change position, the change should not be a very big one. I guess people the likes of S. Miller may be able to discern that kind of small change (just as V. Rossi seems to be able to detect a 2mm change in fork height) but I suspect that few mere mortals can notice the difference. I'd be surprised if most people would notice the reduction in effective steered mass when a trials bike (to the best of my knowledge) normally isn't "flicked" down with a quick snap of the steering. Roadracers do those kind of sharp steering inputs, but even there what you are mostly noticing is the the gyro effects of the front wheel and disc rotors. Put on a lighter tire and significantly lighter rim/wheel and 300+mm brake rotors and that change gets noticeable during those sharp steering inputs at speed. Extra stability would normally come about from reducing the offset of the axle from the steering axis and so increasing trail. Putting center axle forks in a set of leading axle triple clamps would give you that, hopefully without the more rearward wheel position causing it to bottom out on the exhaust pipe at full bump. But it also reduces the wheelbase which would tend to reduce the straight-line stability a little, while shifting a little bit of the weight distribution more forward which should help to increase the stability. Changing just one thing gets very difficult to do as you need to watch multiple variables. It would be interesting to do some blind tests to see if people could actually notice the difference in the change of polar moment. You wouldn't even have to change forks. Get a couple of 1-2 lbf bars of lead that will fit inside of the fork springs and figure out how to attach them to the bottom of the fork caps. Put a bag over the upper part of the forks between the triple clamps (or something that shields that area from the rider's view). Now have someone move the lead bars from the fork cap to taped to the front of the fork tube to the back of the fork tube (f that is possible without it cutting down on the steering lock) to not even on the bike at all, varying the position randomly and ensuring the rider doesn't know where the lead is and send the rider through the same section over and over. Do it enough times with enough different changes to give a reasonable sample and record the rider's guess about where the weight is. eta: you could probably avoid fiddling with putting the lead bars inside the forks, just position them front, back and sides of the tubes. That makes it easy to do it all with just duct tape or zip ties. If you want to play with trail have a spare set of the "other" kind of forks from what you normally have. Run the forks as leading axle, swap in the center axle forks, and then swap those for the leading axle forks running reversed for a trailing axle. I think there is about an inch of lead in the Bultaco sliders so that would get you a pretty noticeable change in trail. You'll have to adjust the amount the forks extend through the clamps to keep the steering head angle from changing. Of course, you also end up with changes in wheelbase and weight distribution muddying up the experiment, along with changes in the polar moment of the steered mass from moving the wheel a couple of inches forwards and back. Filling the inner tube with water should increase the gyro effects and make the bike really stable. But when it does finally get knocked off line you may find it difficult to overcome the stability of the new direction. As to damping, a friend has done a fair bit of work on four-stroke Husqvarnas over the years, including fork/rear damper valving. He told me that he's seen rear dampers from the same model and year bikes that were not very many serial numbers apart have very different shim stack specs from the factory. It doesn't matter how trick the damper is, if it is valved for someone who weighs 50 pounds different and who goes 20% slower or faster the external adjusters are unlikely to have enough range to get it anywhere close to being right. And if you don't have that adjustment available (as on our vintage stuff) you are really out of luck. cheers, Michael

The steering angle is determined by the axis through the steering bearings in the frame. The forks could only change it by being grossly longer or shorter than the originals and so tipping the frame up or down. Parallel vs non-parallel triple clamps change the wheel path and how quickly trail is lost or gained as the suspension collapses and the axle moves towards or away from the steering axis. Generally, non-parallel clamps will have more offset in the lower clamp and they'll lose trail more slowly because the axle now moves towards the steering axis instead of paralleling it. If you kicked the lower clamp way out you could get it to where the offset decreased quicker to increase the trail faster than the change of rake from the steering head dropping causes trail to decrease. Go to Tony Foale's website and download his free steering geometry calculator to make it easier to see what changes in offset etc do to real trail and ground trail. IIRC Tony had a KT250 for a while when he was in England. cheers, Michael

Neil, I ride the vintage novice line. I've gotten to where I can go through a trial now and then without falling off all day. But my skill (or lack thereof) is what hampers me, not my riding gear. After about 36 years of wearing all the protective gear I can afford in MX, trials and roadracing, it is more distracting to me to not be wearing it. The last time I tried on an open face helmet I felt very exposed and distracted. I will mention that I've worn glasses from long before I started riding, and protecting them and the rest of the face is a pretty well ingrained habit. The full MX gear (but trials boots) is more likely to give me a bit of a mental boost to try something a little more difficult than usual, as I can feel like I'm less likely to be injured if it goes wrong. I don't bounce as well as I used to. Actually, I don't remember bouncing all that well in my youth. I prefer to make my blood offerings in the garage instead of while riding. cheers, Michael

Use some rosin core solder as it squishes with less pressure than the solid stuff does. cheers, Michael

One of my earliest dirt bike crash memories is of having the end of the handlebar of my 185 Suzuki hitting me in the mouth, leaving me thinking "wow, this Jofa mouthguard thing (just like Joel Robert wears) is really nice, that didn't hurt too bad and I still have all my teeth." I have another memory of falling of my B50MX and thinking "sliding along on my back doesn't hurt while I'm wearing this back protector." I've seen trials riders wandering around dazed after smacking their heads, and I know of others who broke bones in a big "in section" crash. Maybe ace trials riders need to ride nearly naked in order to not lose out on the sensitivity needed to leap tall boulders in a single bound. They probably don't fall off anyway. Neither of those applies to my trials riding. For me, falling of is a "when" not "if" proposition and I'll continue to dress for that eventuality. cheers, Michael

Jay, if you hadn't built the bike I wouldn't have been able to take a photo of it, so fair is fair. Setting squish clearances can make so much difference in things, especially in re detonation. People who want to add extra gaskets that widen squish (presuming they actually have some) in an attempt to lower the compression are just going at it the wrong way and may end up with an engine that is even more prone to detonation. A friend of mine has been known to not only weld in the chambers on TL Hondas to get some squish, but then build up the gasket face with weld too. This lets him have a larger volume combustion chamber (due to the extra depth) for the lower compression and the squish area too. He does then have to lengthen the cam chain, but he figures it is worth it. After I welded up the KT head and machined in the right level for the squish band I tried to recover some volume by grinding around in the top of the combustion chamber. Your best bet is to do what I forgot to do, which is measure the chamber volume before you start. Then you have something to shoot for. A low compression head with added squish bands for a two stroke probably needs to be a thicker casting than stock, unless you are lucky enough to have a head that uses a long reach plug and has enough meat around the stock combustion chamber to allow you to machine the head thinner from the inside of the chamber. Those little combustion chambers that you can see under the water jackets on some roadrace engines must be really handy as they can be made fairly readily on a lathe and mill without having to worry about starting with a much bigger piece of aluminum and then putting fins in too. If you were to do a new casting for Hodaka heads I'd suggest you design it thick enough to work as a trials head (large volume chamber) and then just machine away on the gasket face to reduce the volume for a high compression race head. I know people who are serious RR tuning types (TZ stuff) and they get into calculating the speed of the gas being forced out the squish area and figuring out what angles the squish band should be at, how wide it should be, etc etc etc. I think for a trials engine if you can get some functioning squish without driving the compression up you're probably making enough of an improvement so that the arcane technical details shouldn't be much of a worry. And the RR types are looking at 10-12K RPM operating speeds which is a bit different environment from a trials bike. Once you get the squish working and helping the turbulence in the combustion chamber (this may be something else the RR types are worrying about if they don't want to interrupt some carefully figured out scheme of loop scavenging) you can often back off the ignition timing too. cheers, Michael

I'll mention that there may be some variance in difficulty depending on what part of the country you are in. A friend of mine (348 Cota) who rides about as well (or poorly) as I do on the 3 line moved from the SF Bay area to the east coast (Philadelphia PA). He said that the 3 line there seemed more like the 2 lines out here, and he really struggled with them. cheers, Michael

I think you can get Roadholders converted to modern cartridges by Ron Williams at Maxton and several other sources in the UK, as well as by people in Aus/NZ. I'd be surprised if Racetech's cartridge emulators and other products were not being sold in the UK by someone. In any event, in this modern world buying in from half-way around the world is not uncommon. But the things I mentioned don't seem any fancier than what I read is happening in the UK vintage trials suspension scene so I don't expect that US sections are more difficult than what you get to ride. But then since I only ride the novice line I'm not the one to comment on how the expert lines might compare. A TLS is going to be less effective if you are trying to stop from hurtling backwards down a slope. Of course, by then you've already got a five, but it still would be nice to have a brake that worked in both directions. Making sure the drum is round and you have good linings that are arced in to the drum makes a lot of difference on most brakees. The small conical Yamaha front brake as was used on the DT2MX and many later bikes stops very well (I put one on my 125 Maico to replace the full-width drum it came with), is fairly light, and pretty common. If it works fine for MX it would seem to be plenty strong enough for trials use. cheers, Michael

I suspect that is a Premier Lightweight class bike as Dick seems to mostly build Premier bikes for trials and MX. It sure looks early to mid-1960s. http://www.localhistory.scit.wlv.ac.uk/Mus...rcycles/DMW.htm has some interesting history and photos on DMW. But the Internet is far from full of DMW information. cheers, Michael

Hi Doug, I didn't know that many people and I didn't really get started until probably 1973 (MX was what first caught my attention and I raced my TS185 in Sept 71 at Volcano Cliffs, moved up to a TM400R (the former Motorsport shop bike -- I worked there part time for my first couple of years at UNM), a 1972 125 Maico from Bob's MX and Kart Shop, and finally a 250 Griffon). I remember Carl Shipman (247 Cota) who had the line of "Dirt Rider" products and who wrote several books including "How to ride observed trials just for fun!" The photos in that were mostly from the NMTA events (and I'm even in the background of a few, but that was when I was mostly like you just checking things out). Some of the names I pulled out of the book are: Don Anderson (Bultaco), Bill Anderson, Sue Bryner (Saracen and 16 years old at the time so she may be who you were thinking of), Harold Shepard (Shep) (Bultaco), Leo Kurowski (MAR), Walter Nance (Bultaco), Bud Cole (SL125 Honda), Wayne Ebaugh (MAR), Dave Boland (MAR), Gene Hirscman. It has been a while since I last looked at the book and it was a nice walk down memory lane! After I got my Sherpa T I remember Wiltz Wagner, Bob Nickelsen and Elliot Shultz coming down from Colorado and I took a morning trials school with them. cheers, Michael

I can't recall if my KT250 had a squish band that didn't squish or if it was just an open chamber, but I welded it up and remachined it to have a real squish band. After that I retarded the timing from stock. I made a survey of all the trials port specs I could find and made some minor modifications to bring anything on the KT that seemed too far away from the common number back into that range. The new pipe with long header finished off the engine mods. It seems to run a bit better and doesn't have detonation problems. You sure can't trust that the factory (whichever factory it might be) came anywhere close to where they were aiming on a production bike. The works bikes will have the extra attention done to fix that stuff, but the retail customer pays their money and takes their chances. cheers, Michael

Cheetah (Gollner?) seems to have offered a disc brake on a trials bike in the late 60s from articles I've seen. It was a heavy car disc brake, but it was a disc brake. And I've seen Campy mechanical discs on early 70's trials specials. I don't see anything wrong with period parts or reasonably accurate replicas of them. Putting a 6 piston caliper and 320mm floating carbon rotor on your G50 Metisse that came with a Rickman disc on the front is pretty obviously getting out of the period. You can fit Race Tech cartridge emulators to the Ceriani/Betor/Telesco etc 35mm damper rod forks and that's invisible from the outside. There are people who supply conversions to slip late model sportbike cartridges in your Roadholders (I think I've seen photos of some P65 bikes with long Roadholders on them), and again that's (AFAIK) invisible to the viewer. If someone shows up with something obviously way out of the period it should be pretty easy to spot that and ask them to fix it before the next event. There is always going to be someone who is going to go past the point where it looks like diminishing returns have set in. If they can do that and have it look acceptable, more power to them. The thing is, the vast majority of people probably have 5 year old fork oil in their bikes (or at least they think they put some in 5 years ago) and whatever springs came in the forks which may or may not be vaguely close to what they need for their weight. And even if I build something I think is cool (and looks period) that is a significant improvement, I'm still going to be collecting points and falling off on the Novice line and having good riders on stock TL125s do better when the scores are tallied at the end of the day. Isn't fun supposed to be the goal? There's always going to be someone better or worse than you are so try to find someone about your level and have some friendly competition to see who is the best lower-midpack Novice rider on a given day. For me fiddling with the bike is part of the fun. I changed out parts and modified things when I was riding in the period and I intend to do similar types of things to the bikes now. I've known some fast racers who had the "if I don't think I have a chance of winning I won't come out" attitude. A lot of those people I haven't seen for a long time because they could no longer win so they stopped riding. That's their choice but it seems kind of sad. If someone wants to spend a fortune to win an amateur vintage trials championship, that championship and a couple of dollars may be enough to buy them a cup of coffee at the local shop where the barista asks "is that a Harley in your truck?" If that's they way they want to spend their money, as long as they can do it within the rules (and hopefully within the spirit as well as the letter of the rules) I'm all for that. Maybe they'll spend money on something that looks like something I can copy in my shop and use on my bike. AHRMA Modern Classic is the period of bike that interests me. 7" and 4" suspension limits eliminates a lot of the incentive to chop up a seat subframe to increase rear travel, because that just makes you illegal. Build your own frame? Why not? You can run a stock RL250 Suzuki or you can buy a period Beamish Suzuki and have something that is probably as light as you might build at home. Not everyone can afford to buy in a trick period or replica frame but they may have some knowledge and a torch and the minimal tooling you need to build a frame. If whatever they build can pass the "where'd you get that? Oh, I found it in a barn. Cool, I remember seeing something like that back in 1973 . . ." test it looks period enough to be good to be in the event. Maybe the twinshock class has issues that can't be as easily dealt with as Modern Classic does. I don't know as I haven't had a chance to get familiar with what is going on in that area. majestyman340, the tubing is the cheapest part of the frame. You may spend more money on fork and swing arm pivot bearings than you do on steel, and you'll spend way more than either of those in time building the thing (presuming you put a real-world valuation on your time). If your application doesn't need the extra strength of 531 or 4130, why spend the extra money on it? I've learned to start trimming the long sections of tube first so when you cut it too short you can hopefully have it be long enough to use on the next shorter tube instead of having to consider it scrap. I'd rather toss inexpensive scrap in the bucket than expensive scrap. cheers, Michael

IIRC (and this is from 30 years ago) the frame on my 1974 Sherpa T was pretty light (it was the newer style with the diagonal tube running from the back of the tank down to the swing arm pivot). It also had the light aluminum hubs with the chromed braking surface. You aren't going to get a lot lighter than that. Most 70s trials frames don't have much in the way of tubing in them, and what is there tends to be pretty small OD, so I don't think anyone is going to see huge improvements with a "trick" frame the way you do with something like a Matchless comp single frame. A lot of the weight in the older bikes is in the engines. A B50 or TT500 engine is 90-95 lbf while a 2005 YZ250F modern 4 stroke single engine I have is 54 lbf complete with carb, ignition and levers. A YZ450 is just a few pounds heavier. As I mentioned above, you don't need 531 or T45 or 4130 to build a frame, but if you are using exposed thin-wall tubes then the stronger tube will help to reduce the amount of denting that takes place when you drop it. And if you build a frame with tubes loaded in bending (as was not uncommon) you may need the extra strength of the 531 etc to keep the frame from bending and staying bent. The thing is that not only were there a fairly wide variety of aftermarket frames made and sold "in the period" there were also a number of DIY chassis built by enthusiasts. I've tried to collect photos of as many of those types of limited production or one-off frames as I can find on my website. And I still keep running across ones I've never seen before. Just last night I was thumbing through some early Off Road Reviews (Deryk has given me permission to use selected photos since I make a point of attributing the source and photographer) and spotted a Nick Nicholl's photo of fuel-bearing spine-frame Bantam at the 1969 SSDT (with added on tank) that I don't recall seeing before. And then there's the article on the monoshock Goldie scrambler that was 290 lbf with stock BSA wheels and was built and raced in the early 1960s. There's nothing new under the sun. The UK was an obvious hotbed of DIY stuff. I've got a good collection of MCN/MCW/MCS from the mid-60s forward and there are lots of "readers specials" pictured - MX, trials, grasstrack and RR. The continent is a bit more of a grey area but I've got photos of DIY frames/heavily modified production frames from there too. Here in the USA we didn't have as much of a trials scene but we did have people like Bill Grapevine and his Maverick (and GRM) trials bikes and the guys at PABATCO with their Hodaka specials, and there are certainly lots of MX, roadrace and dirt track aftermarket and DIY frames that were done over here. I think the important thing is to keep a reasonably period appearance. That means the parts need to look right and be of the style that was found in the time. If you can't see it, don't worry about it because you aren't going to be tearing down engines after a trial to see if someone has carbon-fiber reeds instead of steel reeds. In any event, the riders are still going to be the limiting factor in the vast majority of cases. I think more specials would add to the scene. Modern MX and roadrace is pretty boring because everyone is on pretty standard production bikes these days. Maybe you can find a singles or twins racer with a DIY frame to look at, but for the rest you can just take your Yoshimura catalog and go to the showroom and see all the same bikes as at the races. cheers, Michael

Ooops, just noticed that I had a typo. Both of those "Fraser 125" frames were from MCW, not MCW and MCN. The later frame photo, like your DMW, had text with it along the lines of "Because the USA market wouldn't accept the MK1's unit tank/seat assy they went to a 4" OD spine frame holding the fuel. A dummy tank cover is fitted. Down tubes were added at dealers' request, though the prior version got along without them just fine." That seems a pretty direct link back to the TL frame photo they (MCW) published 10 months earlier. Curiouser and curiouser. cheers, Michael