feetupfun

Here is what it looks like with the Explorer tank.

The Explorer is an easy conversion unless you want the same wheelbase as the Mk1 MAR. The Explorer is based on the Mk2 MAR which has a longer swingarm than the Mk1 MAR so if you want the short wheelbase you will need to shorten the Explorer arm or get a MK 1 swingarm. If you fit a shorter swingarm to the Explorer, the bottom mudguard mount needs to me modified to provide rear tyre clearance. My OSSA trials bike is based on an Explorer and has been fitted with a redecorated MAR tank, MAR seat and a MK1 MAR swingarm. It is great to ride. The photo was taken yesterday at a trial.

This model Alpina can be made into a very nice trials bike, very much like the M199 Sherpa T but how good depends on how far you want to go with the conversion. Yes the tank and seat are obvious. The airbox and sidecovers arrangement on that Alpina is much wider than the Sherpa T. Replica M198 Sherpa T airboxes and sidecovers are available. An early model Sherpa T or Alpina funnel type air filter would also work but would be a lot louder (induction noise) The wheel hubs on that model Alpina are Pursang/Frontera type and as such are lots stronger/heavier than Sherpa T hubs. The triple clamps are Pursang type (to provide more trail in the steering geometry) so to get the trail down to the same as Sherpa T, you will need Sherpa T triple clamps. The M213 frame has good geometry for trials, but has extra bits that could be cut off to save weight like the rear grab rail. The motor setup should be fine for trials as it is, but you will need a very big rear sprocket to get first gear slow enough, because the lower gears are taller in the Alpina than on the Sherpa T while 5th is about the same. If it still has the original Betor shocks, the springs will be a much higher rate than ideal for trials. Regards David

The bit I'm a bit lost with is that you are mentioning the relative cost of things that priceless. Since when does the cost of your hobby/dreams/memories come into the equation? Yes my twinshocks have cost lots of $$$ and I've spent thousands of hours in my workshop but riding those bikes is still probably the best value for money fun I have ever had in my life. I suspect that my lukewarm feelings about TY monos are because I eased up on riding trials in about 1980 and it was 1994 before I became fully obsessed again. The years of riding from 1973 to 1980 are burned forever into my psyche. I suspect that you have a connection with TY monos for a similar reason.

If Oliver's Dad looks at this forum or of someone else knows, please tell if Oliver is using the rear brake to help with balance or is it all throttle control? Thanks David (yes my kid rides an OSET 16)

What election?

Did you mean to type "sold" or "solid"? If you meant "sold", then I think you need to think again. Maybe you are a bit young to have witnessed what happened in the 1970s but Bultaco Sherpa Ts and Yamaha twinshock trials bikes would both have outsold air-cooled Yamaha monos by a ratio of at least 10 to 1, and are also well loved by the riders of their era. I do think a class for air cooled monos would be good for the people who like riding them.

I can't see much of the fork caps in that photo but the caps look like they are of modern manufacture to me rather than made by Montesa. Schrader valves are simply the type of valves that are used on car and bike tyre tubes and act as a non-return valve to hold the gas in and you push a litle pin in the end to let the gas pressure out. A different type of gas valve was used in the fork caps of a few old trials bikes like Bultaco Sherpa Ts and Kawasaki KTs. These are called vented caps.

An Alpina sold in 1975 might be a M115(250)/116(350) or a M137(250)/138(350). The M137/138 is the type of Alpina that is furthest removed in design concept from the Sherpa T of the same year. I'm not sure about the M116/117 as the ones I have came with triple clamps removed and mixed up in a box. After the M137/138 Alpinas came Alpina models (M212/213) that went back to being very similar in geometry and design to the 1978 M198 Sherpa T. The M137/138 has the Pursang triple clamps as Woody mentioned and a long swingarm - I have a restored M138 Alpina and I can tell you it would make a poor trials bike compared with one of the Alpina models that are very similar to Sherpa Ts. The first Alpinas were the M85 (250) and M99 (325) and it is these models that are most like the Sherpa Ts of the same era, differing mainly in the internal gearbox ratios and the seat/tank. If you can advise the model (the M number is the first part of the engine and frame numbers) of your Alpina or post a photo it would help identify it.

If it runs with the choke on, then there is fuel getting to the float bowl. If it stops when you turn the choke off, then either the pilot jet or the main jet or both jets are blocked. You haven't given enough info to differentiate/diagnose further.

Yes there is no friction at the spring/tube surface if you have no springs, but the friction at the fork seals goes up dramatically with increasing air pressure which is why very few manufacturers used air springing on its own. Most had air and steel springs together. Any bike with sealed fork caps is making use of the air inside as a spring, whether the caps have the facility to adjust the pressure (schrader valves) or not. Jaan, you can buy new springs for the Cota 348/349 but most people just add a bit more preload to the spring. When the springs get so sagged that to get the preload right, you have to put in enough spacers that the coils touch each other before the forks bottom, it is time for new springs. Sagged single-rate springs have the same spring rate as new springs, they are just shorter overall when relaxed - hence needing longer spacers to achieve the same preload force. In the case of my 1976 348, I have about 10mm more spacer length than standard, and ride with the pressure set at atmospheric pressure with the forks topped out. Be careful when comparing settings from one 348 with another 348 because some came with higher rate springs than others. If you have the low rate springs, as Peter says, you will need to run some air pressure in them.

If it is a standard 348 kickstart lever, it will bend OK cold but it will be much easier to bend if you heat it up. A standard lever will not shatter. Either way you will be wrecking the plating finish. It must have taken quite a hit to bend it out of shape as they are very strong - as you will find if you try and bend it cold.

Yes it should move a wee bit. Its called a floating disc and helps the disc stay nice and flat when it gets hot, and ensures that the disc can move to align with the pad surfaces when braking if there is any slight difference in alignment without flexing the disc.

Yes it is a matter of opinion and I didn't want yours to be the only one.

I have to disagree about sliding TY175 forks down flush. Whatever shockie length, footpeg location or handlebar rise, sliding the forks tubes down flush with the top clamp might improve the ground clearance but it makes the steering in sections worse, not better.

The 88 model TY250 has a completely different hub so has a different cable to the twinshock TY

I don't know how common they are around the world but there was one a bit like that in our club until 2 years ago when he finally got sick of my complaining and converted it back to being a lovely, standard, M198A. As a monoshock it looked hideous to my eyes, having USD forks from an early 1990s Fantic and a modified Pursang swingarm and front and rear disc brakes. The linkage mechanism and shock were from a TY250N.

http://www.southwestmontesa.com/ http://www.inmotiontrials.com/

Stork I posted the spacer details including a photo on the Trials Australia website this afternoon. David Lahey

Yes the Hebos do have a different angle. I always felt like I was standing on the leading edge of my Rev3 footpegs so it was a great relief to ride it with Hebo pegs. My feet and legs were much happier.

I haven't had a van for many years now and am interested in getting one for trials bike transport. The Vito is by far the most popular bike transporting van here. The other vans I see mentioned in this forum are available here with the exception of the little Transit but in the popularity stakes the merc Vito leaves the others for dead. What I'm interested in is why is it so? What is wrong with the Vee Dub and the Citroen? We also get a newcomer from Hyundai (the iLoad) that is a Vito look-alike and I haven't heard anything good or bad about them yet.

Neither type of tank shown in the slide show looks like anything I've seen on a modern motorcycle. My guess would be that both shapes are recently made and purpose built to go on a bicycle and the especially ugly shape with the side bulges is intended to appear like something from a 1960s Eastern bloc motorcycle. They are probably made from fibreglass.

TY80 small wheel tank too short TY80 big wheel tank too long TY175 tank too short A DT tank will be too wide at the back end Most twinshock Yamaha dirt bike tanks will "fit" but it would pretty lucky to get one that looks good. Even YZ125C tanks look strange on a TY. Surely there are the later model (aluminium) TY250 tanks available from wreckers. They look fine on an A model. David

Yes it is the wrong kickstart lever. I'm not sure if the 247 arrangement is the same as the 348 but if it is, then yes there should be a stop but the stop is a bit fragile and yours may have been broken by overrotation of the kickstart shaft. Remove the magneto flywheel cover and all will be revealed. There is lots of info available here about your 247 http://www.southwestmontesa.com/ David

Sorry Woody I had the metallic green paint matched by a spraypainter from an old KT sidecover. I suspect that is the sort of thing that most people have done. The spraypainter told me there were no listings (or he didn't have access to any listings) of paint numbers for old dirt bikes like the KT. David