woody

No different from points in principle, if it's advanced the firing point is brought forward so that it fires further down the cylinder - this makes the engine respond quicker. If it's retarded it fires later, or, closer to top dead centre, which makes the engine pick up slower. With points, the timing stays at the same setting throughout the entire rev range, therefore if you set the timing retarded to make it pick up off idle slower, you may find that it is too retarded at full revs to rev right out. Similarly, if you set it advanced to make the engine pick up quicker, it may knock or detonate at higher revs if it is too advanced. The advance curve on an electronic ignition means that after the first (say 1000rpm for arguments sake) the CDI processor automatically begins to advance the ignition as the revs rise. This means you can set the backplate to a slightly retarded setting to get a slower throttle response off idle, but unlike points, the engine performance isn't then compromised at higher revs due to the ignition being too retarded, as the CDI will advance it as the revs increase. That's about it in a nutshell. The timing for most trials bike can be set between 1.5mm BTDC to 3.5mm BTDC You don't say which ignition you have, if it's Electrex I've no experience of them. If it's the type from Rex Caunt or Bultaco UK. You may find that the default setting is retarded a bit too much, especially on a 175. The 3 small allen bolts that secure the stator to the backplate have more than one mounting hole to screw into in the backplate, which enables the ignition to be fine tuned to suit your purpose by repositioning the stator as required. Turn it clockwise to increase timing, turn it anti-clockwise to retard it. It's just trial and error until you find a setting you're happy with. I'd begin with how it comes.

Use the normal plug, the platinum tipped things are fine for constant high reving like motocross but can foul up when running at low revs. I've had a few TYZ Yams and never fouled a plug in any, although can't remember what plugs I used now - probably BP6ES or 7ES. The TYZ I had from new I never changed the plug in.

The Twinshockshop in the UK should be able to help you with that as they have a source for TLM260 pistons http://www.thetwinshockshop.co.uk/

I think people get too hung up on this twinshock / aircooled mono / o40 / 050 class thing. Ultimately it's about riding a bike you enjoy riding in the type of event you enjoy riding. Why are people so hung up about riding in a specific 'class'. If you like riding a make of bike that just happened to be a twinshock at original manufacture and you ride it on the easy or middle route at modern trials, then there is no reason to question fitting it with discs. If you ride it in a twinshock class, whether that is in a modern or classic trial, then it should have drums fitted. It's an unfair advantage if you are competing against other twinshocks that are period spec. It's cheating. I haven't had a modern bike for about 7 years and ride my Bultacos or Ossas or BSA in whatever trial I like. More in modern trials than classic as it happens, many of which don't have a twinshock class. If I rode the Bultaco only in modern events I'd probably put discs on it as some descents can be a bit hairy (the type you never get in 95% of classic events) and it also makes slow clutch / brake maneouvres much easier as you need an effective back brake to steady the bike when easing around on the clutch. But, as I still use it in classic events then no way should or would I fit it with discs. Some people try to make a twinshock like a modern bike. You can't, it just won't happen. You can improve the steering a bit on some but ultimately it gives no real advantage. I haven't come across a classic section yet that I can't steer my '72 Sherpa around or my KT when I had it (very similar to an older Sherpa) You need to ask yourself why you ride the Cota. If it's because you enjoy it (and they are a good little bike) then that's reason enough. If you're solely competing against modern bikes outside of a twinshock class then there is no problem fitting discs. Against other twinshocks, no, you must see that it is an unfair advantage or cheating? Most riders may not say anything to you at a trial if you did, but you can guarantee there would be a lot of muttering behind your back.

The 'proper' TLM260 with the double disks was an excellent bike, however, not a twinshock, so irrelevant. Honda never made a full size twinshock 2-stroke, only the tiddler. If the budget is £1500 max, then Hondas are off the menu full stop. A TLR250 is £3k minimum plus more to spend if it is in standard trim. Even the 200 is now making over £2k on average. If results / winning is not the objective, merely to have have fun, then then there are quite a few options. As you've had Montesas before, you may gravitate towards them again out of nostalgia and they have produced some very good twinshocks. The problem is parts as they can be hard to find if you need replacements - either engine or cycle parts. Not impossible, but harder than some other makes. The white tank 200 is a great bike, as is the 242 and the last of the 349 range (different frame from the white 349) Monts generally grip very well. Most will easily fall within budget Best all round twinshock was the Fantic 200, a great bike for novices or average riders whilst still plenty good enough for experts to win on. Generally available in good condition within your budget. The 240 can be a bit snappier and not always have the same level of grip as the 200 in less experienced hands. Bultacos are probably the best served for spares with just about everything available. Best model to go for would be a late model 250 either model 198 (last red one) or 198a (all blue one) They are an acquired taste as people like or loathe them. Not as competitive as a 200 Fantic but as that isn't the objective, it doesn't matter. They feel long but turn very well and are stable up rock streams. Decent shocks offer a marked benefit to the feel of the bike as they can feel wooden at the rear. Again, they grip well. A better option than the 325 model which will pull you about with the extra power. Ossa MAR is a forgiving bike, the earlier ones felt more stable, as the later bikes from '76 felt a bit tall. Spares situation is generally not too bad now, not as good as Bultaco but better than Montesa. They can be a bit flat in power delivery but can be perked up if required. The Gripper models feel very high and again, are a bike people love or hate. They perform very well if set up properly and Steve Bisby has a really good example, but probably for a beginner / novice, they'd be a difficult bike to ride - and they are a bitch to work on. Armstrongs are very good bikes, 250 or 310/320. Handle well, grip well, the 250 has plenty of power which is very useable, the 310/320 are very strong motors, not sharp but loads of pull. At the moment, good examples are within your budget as they don't seem too popular, probably because of the spares availability here. Engine spares can be had from Italy but smash the tank, airbox, exhaust and you could be in trouble finding a replacement. They are a bigger bitch to work on than the Gripper. Later bikes had Rotax engines but the Hiro motors are nicer in the Armstrongs. SWM are good bikes and again available within budget. Strong motors, either 240 or 280 Rotax. The clutches can take some setting up and they aren't blessed with the best action, but the motors can be made to run very smoothly so most sections can be ridden without the need for messing with the clutch. Handle well, steer well, decent suspension with Betor or Marzocchi forks. Best example would be a late model with either black frame or blue frame. The Jumbo framed 240 is a nice bike but don't be tempted for a full 350 Jumbo as it will pull your arms out. Very powerfull. Then there are others such as Beamish Suzuki, KT Kawasaki, Aprilia Hiro, Garelli Hiro, but spare will be more difficult to find for these than those above. Finally there is the TY175 Yamaha which you should easily get for within your budget. Light, easy to ride, not overly powerful... but surprisingly capable. Most spares easily attainable - easily cope with a classic trial or easy / beginner route at modern trials. Just about still in budget. The 250 isn't a bad bike, handle well but starting to creep in price now and some engine parts can be hard to source, which isn't a problem with the 175. Engines can be flatter in response compared to the other bikes mentioned but removing the heavy flywheel weight will address that. In truth, all of the above will serve the purpose you need, all will provide perfectly adequate levels of grip with decent condition tyres and good shocks. All have more than enough power. They all behave and handle differently and respond differently to rider input, but all will do the job you need them too.

Honda TLM was only available as the tiddler - they didn't do an adult 2 stroke twinshock.

Higgo - your advert for a MAR flywheel You need to specify which one as there are two types. Although they all look the same, the timing pick up is in two different places. On the early bikes, the hole that the timing pin uses to locate in the stator to set the timing is at about 8 o'clock at TDC. On the later flywheels, around 1974 onwards, that hole is around 5 o'clock as the stator is different. They aren't interchangeable, you have to have matching stator / flywheel

Yes, I think he went a bit awry with his photoshop as he reversed the front and rear of the bike - the front brake and torque are was on the wrong side too.

Yes, the MAR is a lazy responding engine. You can sharpen it up by fitting an enduro flywheel which is about 1.5lbs lighter, or skim a spare MAR flywheel, fit a thin copper head gasket of maybe start with a 1mm gasket instead of the usual 3mm thick spacer. The engine will pick up quicker but the trade off is that it may stall easier at lower revs. The MK1 MAR picked up a bit quicker than the MK2 onwards as it had a slightly smaller crank assembly, hence lighter. The Gripper engine is the same bottom end but with better selector shaft and layshaft bearings. The cylinder porting was different from the MAR and was more motocross orientated for quicker response and more revs, although the MAR will rev out pretty high too. The problem you'll have fitting the Gripper engine is what to do for an exhaust. It uses the motocross type expansion exhaust and no way will you get that onto the MAR chassis. It may work with a conventional exhaust but with the taller fins on the head and the high inlet port, you may have trouble designing an exhaust to fit First thing I'd try is lightening a MAR flywheel, fitting the thin head gasket and making sure the carb is in good order.

All this 'got to learn no stop' stuff is bollocks. Any rider can ride no stop. The problem is with today's bikes and the skills they allow, it is the temptation to stop momentarily to get out of trouble that is the issue, not an inability in skill level to continue moving. Top trials riders have no problem adapting to enduro when they want to do they... a totally different riding style The problem has existed for ages in classic trials which are all non-stop. Get a capable rider on a lightweight modernised pre-65 and if there is a tight-ish turn (and I don't mean a hinge in bike required turn) or a slippery turn that could lose the front wheel and cause a dab, some riders will quickly stop and hop the front for a clean - especially if they feel the front going away. Not because they can't ride no-stop, but because they know that there is a chance of losing the front and having a dab if they do. Having the skill to stop and hop gives them an assured clean as it is highly unlikely they'll get a 5 for it (which is another issue altogether) On original pre65 bikes there was no question of being able to stop and hop out of trouble, you had to take a dab to pull the front back on course. With a modern bike there is a way out, if the rider has the skill to do it. And if they do it quickly enough it will go unpenalised

C15 is 67mm and 500 Triumph is 69mm so it's only an extension of the max oversize and just needs boring to suit. It takes it to 262cc so you're not really going to notice much, if any difference. The 650 Triumph piston is 71mm and takes it to about 277cc which gives it a bit more torque and pull. I can't remember whether you have to widen the head to go with the 71mm piston or not and it might need a thicker liner, again can't remember. You also have to make sure you get a piston with the correct shaped crown in order to keep the correct compression ratio. In truth, the standard bore size has more than enough for any classic trial.

I know what you mean yes, but those mock-ups were done 3 to 4 years ago. I think they did use the back end design of his last 340 though and tidied it up a bit. The best thing they did, which is what I always wanted to do but lack the skill, was shorten the tank and move the seat forward. From '75, the Bultaco tanks were always too long.

You may want to email the club for confirmation as it seems it is correct that from next year, modern fork/mudguard braces won't be acceptable in Scotland, so bear this in mind when getting your forks done - you may want to keep the original mounts for stays.

Nothing like Montesa Ossa etc is accpetable If you're after alloy then the only yokes on the acceptable list are the billet copies from Alan Whitton and others. REH and MP are generally considered pre70 not pre65, so although they're ok most other places, you'd be taking a chance trying to get them accepted in Scotland. You may want to email them for confirmation as the rules seem to change anually now.

It's a mock up done by a stylist, can't remember which one, he did one of the Ossa Gripper too Also did the Bultaco in red

I haven't got the Hiro contact myself, but if I need anything I know someone who can get it, if he isn't carrying it in stock already.

Seth - any idea if the rubber strap to hold the front of the tank is available from anywhere?

Yes, he's a clever *******....

Yes, it's my 320. Bought as a wreck, original but worn out. I think it had been sunk in water as well as run without oil. Needed a complete rebuild. I don't want to think how much it cost to do. I was hoping to give i its first run out tomorrow but been setting sections all day so didn't have time to finish it. Next week hopefully. It's standard apart from lowered pegs, tubeless rim, OKO carb and slimmed down seat. Also has a new alloy airbox as the original is one of the worst to remove / maintain, not to mention fragile. Airbox made by my welder / fabricator mate. It has nothing to with airflow or increasing volume etc. To remove the original involves dismantling half the back end of the bike and just trying to remove or fit the filter is a major ordeal. I wanted one that would just unbolt and lift out through the top of the frame once the tank was off. Servicing is now much easier. Picture below is as I got it, then one of the airbox. Then one of a 310 I acquired which needs a going over although thankfully the engine is pretty good on this one. Still need to strip it though as it was jumping out of first and the kickstart spline has gone.

I understand what you mean about the round tubes but definitely was a 320. The downtube was remade and splits into two like the 250 because the Garelli cylinder is centre port The frame was completely altered more as a styling exercise than anything as the original owner is what you might call a pretty handy welder fabricator and just wanted to re-style his bike and give it a modern look and feel - as I mentioned earlier, this was about 15 years ago and nothing to do with the current ideal promoted by a few that you must do this that and the other to make a twinshock competitive. He just never bothered finishing it at the time, so another mate of mine, Colin from TY Offroad bought it off him a couple of years ago to finish it off. He rode it in a number of Miller rounds and club trials before it went to a new owner. It rode ok, nothing radical but steered quicker than the standard 320 due to the steeper head angle. Ground clearance was higher and the bike felt a bit taller for a taller rider. The engine was very strong due to the sharper porting of the Garelli barrel. Prior to this bike he also did an Aprilia 320 although the mods to that were cosmetic as the frame was not modified. It has custom made tank, seat exhaust and airbox and was ridden for 2 or 3 years in the Sebac series around 1993. The Armstrong was to be a replacement. The Aprilia then sat unused for many years and once again, TY Offroad Colin bought it off him last year and rebuilt it to use in this year's Miller series. It was on show at Telford, see below.

That was my mate's bike and started out as a 320 Armstrong. It's the Armstrong frame, heavily modified, particularly to get the lower seat height. He made the swingarm, airbox, exhaust, tank, seat, plus a host of the ancilliary stuff like brake pedal, brackets, spacers etc. That work was done almost 15 years ago, so no, it's not one of these new-fangled modernised twinshocks... He never finished it at the time so it sat in pieces for all those years and was finally built up and finished a couple of years ago by TY Offroad. The motor is the original Armstrong 320 that has a Garelli barrell and head - more snappy porting than the Armstrong. This is what it started out as - well, apart from a couple of minor mods

Not really, you never saw that many done. They do look much neater with the bashplate though.

6psi may be ok on dry grippy rocks but in mud it's too hard = no grip. The problem with the tubed IRC, if you're a heavier rider, is the soft sidewalls which cause the tyre to roll around at normal pressure. If you're lighter it isn't an issue. The other problem is inconsistency as not all have the problem, some are ok. The tubeless IRC has a stiffer construction and these can be run with a tube on the tubed Akront rims fitted to most European trials bikes, as can a Michelin tubeless. I didn't find the Dunlop tubeless performed as well with a tube fitted as it did without. The Japanese Takasago and DID rims don't seem to readily accept a tubeless tyre

Have a look here at TY Offroad website. He has built two electric start Hondas, there are pictures of both on this page. I've ridden the blue one and it performs very well. http://tyoffroad.weebly.com/restoration--modification.html

As above, looks like a normal 250 flywheel from an early bike - pretty sure it's like the one on my M49 but that's tucked away and I can't get at it. Fitting the 250 flywheel is a way of making the engine pick up quicker due to the lighter weight, so not too unusual to see a 250 flywheel on a 325 motor. The nut does look to be sticking out too far but I can't remember whether it's the same nut on the 250 and 325 engines. The 325 flywheel is deeper, so maybe the 325 nut, if different, sticks out more with the 250 flywheel. Or as someone else mentioned, there could be pack washers behind it or the flywheel isn't fully home on the shaft.