michaelmoore

I suspect the Bultaco isn't going to make a huge improvement in my scores. But I've been hankering after one. Dave, on the rear exhaust box it says "13717-043 Spark Arrestor". Do those numbers look like typical Bultaco part numbers to you? I couldn't find anything on Google. I'm wondering if it is going to be a problem since it lacks "USFS approved" in that and I think all California OHV parks require an approved spark arrestor. I was surprised to see that Bultaco was claiming a spark arrestor was installed. If I have to I figure the most expedient thing to do would be to graft on a 3" Supertrapp disc/end cap. I've got some of those and the steel end caps are properly labeled. But what might be even more expedient than making something would be buying one of these ST arrestors for small engines: http://www.jackssmallengines.com/strap3s.cfm They've got 1"-2" clamp on assemblies. I'd have to make an adaptor to go on the dual pipes on the Bultaco, but after that it looks pretty simple. cheers, Michael

It sure beats my usual "how many boxes does this fit into?" project. Luckily, a trials bike doesn't have a lot of parts. The engine/trans seemed fine so it will hopefully prove to BE fine. I've spotted a few things like the pivot hole on the aluminum rear brake petal is pretty wallowed out so I'll have to do some small remedial machining jobs on things like that. But it generally looks to be in pretty decent shape. I suspect there hasn't been a lot of trials competition in it's recent life. cheers, Michael

I normally avoid looking at eBay or Craig's List as I have trouble resisting temptation. I experienced that problem again today when I brought home a Model 159 350T: The bike seems pretty stock, other than bars, some "Assault" rear dampers (never heard of those before), a Mikuni carb and Sun rims (I didn't notice a crack in the front one until I got home, but it hasn't gone to far so I'm going to try welding it up as the rim looks quite good otherwise). I don't know if those are the Miura/Bultaco accessory plastic fenders or not. One short fin is broken on the cylinder head but I think that is mainly a cosmetic issue. The under engine frame tubes are bowed upwards a bit and it needs sprockets and a chain. The tank has been sealed before and is seeping just a bit . The owner was telling me how it had been sealed and how it didn't leak a drop, and then I pointed out the rubber cushion at the back of the tank that was damp with fuel. The transmission sure is nicer than the one on my friend's Cota 348 that I rode at Mid Ohio a couple weeks ago. No issues with staying in gear and you can come to a stop and snick into neutral without having to fish for it. Just like a Japanese bike. I'll need to give it a good cleaning and see if I spot anything else. It has a fresh set of Cheng Shin trials tires but I've got a set of Michelins on hand that will go on ASAP. I'll have to rig up a spark arrestor for the stock exhaust. The guy I bought it from just trail rode it around on private land, he's never seen anyone else ride a trials bike. He had it set for about a 1200 RPM idle speed. There is no owner's or service manual or any special tools with it so I'll have to find out what the best choice for a manual will be. I'm probably going to need to move it to the off-site storage so it doesn't distract me from finishing up the KT250. I'll definitely measure to see where the Bultaco foot pegs are located before I relocate the KT pegs (next project on the list). It will be interesting to be able to ride them back to back for comparison purposes. I've still got the Bultaco fanny pack that came with my Mo. 125 back in 1974. I'll look forward to wearing it when riding the T. cheers, Michael

Ross, other KT owners have told me that my bike (with porting/cylinder head/pipe mods) is the best running KT they've ridden. I still can fall off/stall on the novice line, so I guess it isn't good enough yet. FWIW, today I welded on the new outrigger swing arm pivot support plates and the bronze bushing mod lets me tighten up the spindle pretty firmly and still have the swinging arm moving with much more freedom than it did before. Next job is the bash plate to replace the under-engine frame tubes that have been removed. After that it looks like I can lower the footpegs about 1.25" or so. Progress is such a novel thing to experience. The OEM engine mountings on the frame will preclude a ring on the OD of the magneto flywheel, so I'll probably have to do a brass weight that mounts on the face of the flywheel, with a spacer for the cover. cheers, Michael

A Camelback is one of the best investments I've made in riding gear. Before, I spent much of the time thinking about how thirsty I was which didn't help what little concentration I could muster. You'll get a lot of different recommendations on diet, but I suspect that if you go the "good clean nutritious natural food" route you'll probably do fine. When I was working out regularly I tried to balance carbs and protein and that seemed to work both for gaining strength and losing a bit of weight. I don't see any need for fancy/expensive supplements. There are plenty of atheletes who don't use them who seem to do just fine without them. cheers, Michael

Hello Dave and David, Yes, Jim's Cota does have the primary flywheel weight installed. AFAIK it is on the stock gearing too, as was my (Model 124?) 325 Bultaco. It would be handy to have motors available to tear down and measure. cheers, Michael

I rode a friend's 348 Cota in an event this past weekend. The last time I rode a 325 Sherpa T was probably about 1976 when I sold my 1974 bike. Keeping in mind that I'm trying to remember back 30 years, it seems like the Cota didn't have as much flywheel mass as the Bultaco. IIRC the Bultaco would plonk along at dead slow in second gear with no problems as the heavy flywheels would keep it going without a lot of attention from me. The Cota seemed happier in first gear at those kind of speeds. If anyone has experience with both bikes I'd be interested to hear what they think about which one had the heavier flywheels. cheers, Michael

I just got home from the event this afternoon. I met Biff and a few other folks from the Internet. I should have a few photos of the trial that a friend took that I'll be able to post later in the week. The sections were fun, but the stream sections did get sloppy later in the day and that made them a bit tougher than some of the West Coast Modern Classic Novice sections. After about three years of not riding any bike at all (including the loaner 348 Cota) it took me a bit of time to get comfortable but I was pretty satisfied with a 10/16/3, with the last loop being 7 cleans and a 3. I was definitely playing it safe with the dabs. The weekend is overkill. You need to have a pit bike or be used to hiking 8-10 miles a day. You'd have to be really determined to ensure you see everything. BTW, the Laverda V6 endurance racer is really cool. Piero Laverda brought that over for the North American Laverda Rally at the event. It's nicely loud too. cheers, Michael

Nobody offered me a bike to ride and free lodging at Donner. My only expense for the week of going to Mid Ohio is going to be the plane ticket, parking at the airport, and my entry fee. Everything else is being handled by my friend who for some reason feels it is worth doing that to get me to come and visit him. Of course, that does also get someone to go with him to an event that is 8 hours away from where he lives so that may have some bearing on things. cheers, Michael

Dave, thanks for the report. Isn't it amazing how problems always occur when you are far from home instead of in your garage with plenty of time to fix things before you leave? Was the air quality OK? Relatives in Reno say the smoke is pretty bad there. I'll be riding at Mid Ohio on the 27th. It will be interesting to see how badly I flounder on a strange bike after not having ridden for several years. Maybe I'll get to meet some other folks from here while I'm there. I'll be easy to pick out: 348 Cota, MC 3, and no doubt one of many middle-aged guys with white beards. cheers, Michael

Megacycle Cams has a unit single trials cam but I don't think they show it in the catalog. Mine is in storage with my BSA stuff so I can't give you the part number. cheers, Michael

Here's a shot of a section at Donner from about 6 or so years back. I wish I was going to have my KT250 together in time to ride, but that's not going to happen. The exposed granite reminds me of some of the terrain we had for trials use in the early 1970s at NMTA events in Albuquerque, NM. cheers, Michael

1.60" (WM1) appears to have been the standard 21" rim width on a trials bike for the last 35+ years. However, the more recent bikes seem to mostly be going to 2.15" (WM3) rear rims instead of the WM2 (1.85") that was standard on the older bikes that I'm familiar with (KT250, etc). cheers, Michael

Whilst doing some googling I spotted this Motobi trials special and thought I'd post it. The frame/swingarm and forks are not OEM Motobi parts. cheers, Michael

A 1984 prototype Jawa with 6 speed transmission and dry clutch. This Wasp-framed 420cc Jawa trials bike had Ceriani forks and weighed in at 210 pounds cheers, Michael

I didn't check the timing marks on mine because I did the cylinder head mods right away and I also extended the stator slots so I could get even more retard than the stock slots allowed. Once you get the squish working you can often dial back the timing significantly. I'm not sure just where it is now, but I'm pretty sure it isn't particularly close to the stock marks. cheers, Michael

From the shape of the tank and the curve at the top of the frame tubes coming up from the swing arm pivot that BSA might be a 441 Victor GP. Those frame tubes on the B50 are straight as you can see here:. cheers, Michael

I've got boxes of them, but they all came with "do not open" stickers on them, so I can't use them. That probe is expensive, but it sure is handy. I can also digitize parts with it though I haven't gotten far enough along to try that out (too many projects, not enough time or energy). The mill has "coordinate system rotation" so I don't have to tram the vise in. I just probe an edge of the part (which I did before probing that corner in the photo) and the mill skews the coordinate system to match the part. That's what the notation on the side of the plate is about. The skew factor for that edge in this vise was .022 degrees (it had been .018 degrees in an earlier operation with a different fixture). cheers, Michael

I haven't done anything on the KT this last week. Instead, I've been working on (and finished this morning) a boring table to attach to the lathe cross slide that will (with some other fixturing) allow me to line bore the KT swing arm pivot. http://www.eurospares.com/lathes.htm The bottom section of that page shows some of the process and the end product, should you have any interest in looking at machine tool stuff. cheers, Michael

You can get bearings with different internal clearances. You might want one with greater clearance if it is going to be pressed onto a shaft with a lot of interference that causes the internal race to grow a bit. The first thing I'd look at is to see if your internal bearing spacer has collapsed. I've seen wheels where the inner spacer rattles around between the bearings. If the outer races of both bearings seat against a shoulder but the inner spacer is too short the bearing life will also be short as the inner races move towards each other. If you have one bearing that doesn't have a shoulder to seat against (say the opposite bearing is against a shoulder and then has a circlip outside it to constrain it in both directions) you could have similar problem if you've got the inner race up tight against the spacer but have driven the outer race too far down the bore. cheers, Michael

Whatever the AMAL MK1 Concentric is made out of, it doesn't last very long. I've seen mention that both bodies and slides were zinc (possibly the Mazak alloy?) and it wouldn't surprise me if some had one part in one metal and the other in a different one. The MKII is supposed to be a lot nicer. It appears that running metals that are too similar in hardness against each other can cause some problems. I sent the 932 Concentrics from my B50MXs out to have the bodies bored and chromed Mikuni slides fitted. The reports I've seen is that modification makes the wear, well, about like that in a Mikuni. The AMAL can meter well (I've heard the MKII Concentrics can be quite good) but the MK1 Concentric won't do it for long because the wear is so rapid. Once the air starts going around the slide instead of under it I doubt you'll have a very happy time with it on a trials bike. http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html http://www.britbike.com/ubb/cgi-bin/ultima...11;t=001129;p=1 http://www.freewebs.com/bsacontent/pdf/ama...tricstuning.pdf http://www.ntnoa.org/Carbs.htm The material on that sites may be of some interest to you if you do persevere with the AMAL. cheers, Michael

Jaan, if the slide in your AMAL is worn then it is very likely the body is too. Putting in a new slide is not going to take care of all the wear. That's why there are people who bore the bodies and sleeve the slides or substitute a Mikuni slide. The AMAL slide and body seem to be made from the same metal and that causes them to wear quickly. Once you get different materials (like an aluminum body and a chromed or brass slide) the wear goes down quite a bit. Also keep in mind that the AMAL is prone to distort if the flange clamp nuts are tightened too heavily. Generally, I think that if you can get away from the AMAL you'll be happier in the long run. cheers, Michael

For use on an AHRMA machine here in the USA the first issue would be "what carb is legal to use on this bike in vintage competition?" The trials group may not be as "sniffy" about that as the roadracers can be, but it always pays to look at the rule book first. IIRC, the Bing was considered to be an improvement over the AMAL Concentric on the 325 Bultacos. My 1974 model had the AMAL. It seemed to work OK but they start wearing out as soon as you take them out of the box. In some of them you can fit a nice chromed brass slide out of a Mikuni VM and solve the body wear issues. But the needles/needle jets seem to wear too and may need to be replaced every season or two depending on how much you ride and how sensitive you are to minor changes in carburetion. A friend was recently buying a lot of jets for some big VM Mikunis that he was fitting to an XS650 Yamaha and he was running into "sorry, we've discontinued those jets/slides" replies from Sudco on some of his orders. So I'd suggest you make sure what you are allowed to run and that you can get parts before you start looking at "which carb actually works the best." cheers, Michael

The smaller front sprocket is also harder on the chain so you may go through sprockets and chains quicker too. If you had one of the old bikes that didn't have much primary reduction and required a dinner-plate sized rear sprocket then going to a smaller rear sprocket might be of use. I can recall people bashing those kinds of big sprockets on rocks and throwing a chain. cheers, Michael

Hi Charlie, Thanks for posting the photo. I lightened it up a bit to show more detail: cheers, Michael