feetupfun

That was very nice Tim. Which one was you?

Jaan If you want to respoke your 348 front wheel with plated spokes, you can use TY175/TY250 front wheel spokes which are readily available and where I live sell for about half the cost of a set of stainless steel spokes. Yamaha plated spokes and nipples set $90. Stainless steel spokes and stainless steel nipples set $180. I've used TY twinshock front wheel spokes in my 348 front wheel to replace some that were missing when I got it and they fit without any modifications. No idea about what other bike spokes fit the rear 348 wheel. If the bike is to be used in harsh conditions, it is usually worth fitting the stainless steel spokes. We rarely ride in anything but dry conditions so stainless steel is often used solely for the bling factor rather than for practical reasons. Some of my twinshock bikes have painted spokes! I've pulled the wheel apart to machine the brake drum and polish the rim, and the spokes have lost their plating but are still fine so I just paint them silver! The first wheel I did like that was about 8 years ago now and the paint is still fine. I wouldn't recommend it if you are going to ride much in the wet though or if you want a bike for concours de elegance. David

For the doggish 348 Headstock "strengthen" may be a repair - they commonly failed there. There was a factory recall/mod to fit extra gusseting on early 348s. Removal of tubes under engine - to increase ground clearance (just like a 349!!) The extra 1" in the top frame tube is to steepen the steering head angle.

I was there and I confess to loving 1970s Akront rims - even or maybe especially the shouldered type. I just don't know why the combination of 1970s Akront rims and stainless steel spokes invokes concern, being that so many of the bikes from then with Akront rims came with stainless steel spokes as standard. Maybe the enquirer is wondering why those same stainless steel spokes often had aluminium nipples??

(USA) http://www.southwestmontesa.com/ (UK) http://www.inmotiontrials.com/ Ball bearings can usually be sourced from local bearing suppliers. You will find that most of the bearings are off-the-shelf.

Yes I've done 4 or 5 with no problems. In fact most of the wheels came with stainless steel spokes as standard. It's a bit of a funny question though. What is so special about 1970s Akront rims?

If you are not bottoming out, then the spring rate is probably OK. To get the preload right, set the ring so that with no rider aboard, the suspension will almost top out ie it settles with the shockies about 5mm from being fully extended. I am a little bit surprised that you at 14 stone are not bottoming out Betors with 40lb springs. I have 50lb springs on a set of Betors on a TY250 and also weigh about 14 stone and do bottom them out regularly on big landings. I would have thought a Fantic having more leverage on the shockies would have been even more prone to bottoming out.

Put soft plasticene (oil based modelling clay) in a layer about 6mm thick on top of the piston and refit the head. Carefully bump the cylinder loose by turning the crankshaft. When the gasket joint lets go, take the cylinder head back off and lift the cylinder off the rest of the way by hand.

Tom I'm a little bit lighter than you at about 205 pounds and ride 1970s trials bikes. There are plenty of guys your weight successfully riding old trials bikes and yes you can easily set up the suspension to suit. Modern shockies for old trials bikes can be easily bought with a range of spring rates and with standard damping that works great. I would recommend 60lb/inch shockie springs for your weight. They come in stiffness increments of 10lb/inch. They are way better quality and performance than what came new on your Sherpa T. Falcon and Betor brand shockies are popular and suitable. I have fitted Matador springs in my M49 Sherpa T forks, and have increased the preload over standard by about 20mm and use 20WT fork oil. Seeing you are a Bultaco nut, have a rummage throught your 35mm Betor forks parts and see if you can find some springs with a higher rate. If not there are plenty of suppliers with new springs for Bultaco Betor forks. By the way, the ideal suspension sag for trials use is lots more than for speed type bikes. I use 50% sag with rider aboard and 5 mm sag without rider.

Yes you are right. The change to being allowed to stop/reverse without penalty till your foot went down did happen during the later part of the twinshock era. However being a certain age, the bikes I want to see used in competition are from an earlier time. One that springs to mind is the Cota 348. When I ride my 348 in events that are suited to stop-start riding, the 348 is hard work compared with the OSSA MAR, KT250 or any Yamaha, mainly due to the clutch action. We have a once-a-year event that is run to no-stop rules, and the 348 is just as easy to use and maybe even better than some of the others in those conditions. I'm not alone in choosing not to ride their 348 in events with modern rules, instead favouring a bike with a nice clutch. Part of it is to get a lower score, but mostly it is to be able to ride all day without being beaten up too much by the bike. I suspect that in the UK, the sections that twinshock bikes are ridden in are generally more suitable for clutch out riding, so there may not be such a divide between the suitability of different bikes there.

Have you got a decent photo of the Alpina tail-light you are seeking? I have some Bultaco electrical items including tail lights that I don't need but do not know what models they are for.

I reckon when it comes to the twinshock bikes, there are some that are much more suited to stopping than others, mainly due to action of the clutch. When the twinshock bikes were made, the rules penalised stopping, so it didn't matter what the clutch was like and those bikes were not at a disadvantage. Here in OZ, almost all twinshock competition riding is to modern, stopping-allowed rules. By allowing stopping, the bikes with suitable clutches for stop type riding have become more popular than the others. My concern is that there are lots of twinshocks that are not being used in competition, due to their being at a disadvantage under stopping-allowed rules. I enjoy riding both non-stop and stop type trials equally, but would love to see more variety in the range of bikes being ridden in twinshock class so would be happy to ride twinshock as non-stop all the time if that would make a difference.

I'm not totally sure what you are asking but it is common for a new bike to be sold in a different year to when it was made (sold as a superceded model). In the case of Yamaha twinshocks, the last model may have been constructed in 1981, but the last of the bikes constructed in 1981 might not have been sold until 1985. To me they are still a 1981 model but some people may call them a 1985 model, because they were sold new in 1985.

The answer depends on what you mean by making monoshock bikes. Yamaha made works monoshock trials bikes in the mid 1970s that were non-linkage (cantilever) type. These were not available for sale to the public. Yamaha started selling single shock trials bikes in 1984 but the design was nothing like the works bikes of ten years before and had a linkage type arrangement for the rear shock (monocross). Twinshock Yamaha trials bikes continued to be sold up until and probably even after 1984 (leftover unsold production) but while the graphics changed over time and were different in different markets around the world, were mechanically unchanged from the models first sold in 1976. 1973/74 and 1975 models are mechanically slightly different to the 1976 and later twinshock models.

It doesn't look like the standard tank for that bike. Here's a TY250 with a white TY250 tank for comparison purposes.

There are good photos of one of those cantilever OSSAs in a recent VMX magazine. From the photos there you can see one reason why that concept didn't work out that well - there is no space to fit an airbox. I can't help but think that some manufacturers had a bit of a rush of blood to the head at the time when Yamaha started selling their cantilever MX bikes and then the Mick Andrews works bike appeared and seemed to go well. In all likelyhood, the Yamaha cantilever design on Micks works bike did not work as well as the moved-up/laid down twinshock designs later seen on Fantics, SWMs, Majestys and others, due to the higher centre of gravity, greater mass and greater unsprung mass of the cantilever design compared with a good twin shock design.

Yes the wheel hubs are the same on all the twinshock TY175 and TY250 models. However there are some minor differences in the brake actuating arms and brake backing plates of some models - ie some have steel arms while most have aluminium arms and some have inspection holes in the backing plates. The differences do not prevent interchangability.

If it happened suddenly, I would guess that you have a split in the centre section of the exhaust pipe. Have a good look along the welds.

Thanks Tim. That is the most informative story I have ever seen in the mainstream media about motorbike racing. I wonder of there any lessons in that story for us regarding the popularity of Motorcycle Trials? David

Woody who do I contact about buying a replacement ignition to fit a MAR? Thanks David

The 1983 349 is better to ride and harder to get parts for so it depends on how complete and in what condition they are as to which one is better. Why decide anyway? If you like 1980s Montys, just buy both and enjoy comparing them.

I wouldn't single out Majesty parts prices on that. The prices for the Majesty fuel tanks are similar to prices for replica fuel tanks for other bikes of the era.

It's just the brilliant Aussie sunshine ScrumpyJack. This photo shows the colour better

Here is what one of the French aluminium replica tanks looks like on a 250 Godden Majesty

After the discussion on KT250 steering geometry on this string, there has been a bit of experimentation going on over here in OZ. While I was continuing to try multiple different setups with the KT forks, another Aussie just went ahead and tried fitting forks and wheel from a TY250, retaining the KT triple clamps. Soon after I heard how good the steering became, I set my KT up the same and we both think it works very well. KT purists will probably miss enjoying the visual appeal of the polished conical hub and extravagant brake arm setup but once they go for a ride, they may be won over. A word of warning though - the standard TY front guard as seen in my pictures touches the exhaust. It doesn't hit hard enough to affect the steering but does put small scratches in the finish of the guard. I'm working out what alternative guard to use. The KT in the pictures has 340mm shockies and I have also tried 360mm shockies. The bike steers very much like a TY250 now with either length shockies on it. For people with an interest in the change to the dimensions, sorry but I haven't measured anything exactly but by eyeball the front axle is about 25mm rearwards (in-line axle) and the steering head is about 25mm lower (shorter length forks) as a result of the changes. David Lahey