feetupfun

Are you centring the drum on the shoes as you tighten the axle? Are the wheel bearing outers loose in their seats? Are the wheel bearings worn? Is the axle nut tight enough to hold the backing plate in position? Is the drum friction surface grooved or worn unevenly? Any of these things could give the symptoms you have mentioned (spongy feeling).

That certainly is a pretty unusual altitude to ride a trials bike. You will certainly benefit from reducing your jetting but I have no idea how far having only jetted for a two stroke riding up to 4000 feet ASL. For that I changed the main jet from a 240 to a 180 (Yamaha TY175). There was a fellow who used to post on this site from Indonesia who uses his TY250Z for mountain trail riding in Indonesia at very high altitudes. That being the same motor he may be able to give some guidance. I suggest you post in the Yamaha and maybe Techincal Help forums. It may also be helpful to someone who has jetted a bike for such low density air to know how cold it will be where you will be riding.

The cost of living must be different here. All the talk about how expensive modern trials bikes had me get out the calculator and do some figuring. Based on what a first year apprentice machinist is paid here now ($AU18000 PA) and what I was paid in 1977 for the same job ($AU2900 PA), a new trials bike ($AU1400 Sherpa in 1977 and $AU8500 Beta Rev3 in 2006) both cost 6 months pay. Depreciation rates on trials bikes here are generally $1500 for the first year and then $1000 per year until the bike is about 5 years old by which time bike condition is far more important than the age of the bike.

That frame in the Dirt Bike magazine test may well be a Sammy Miller frame made for a Sherpa and then modified in the US by <mention of this company is not permitted on Trials Central> Specialties to fit the TL250 motor.

The sections for twinshock bikes where I live provide a lower risk of injury with sufficient technical challenge. The twinshock sections are also less tiring which means I can enjoy riding all day.

There is always the option of having a replica frame made but the cost factor is considerable and there are very few people willing to pay. There is lots of labour required to copy a frame and if the production run is only a few dozen frames as it would probably be for people who want to build a TL250 motor Seely replica, you could expect to pay $1500 US to $2000 US for each replica frame.

Craig Mawlam was advertising twinshock Jialing powered trials bikes last year. His majesty moto website doesn't load any more. If you want to make contact with Craig, I think he is eBay seller "c1crm"

I'm glad you are coming to your senses on this. Did you really think you could build a replica of a Honda works trials bike for less $$ than the cost of a modern production bike? What you seemed to be seeking was a high spec bike with many custom built parts. For that you should expect to pay many times the price of a new current model trials bike (unless you provide the labour). Twinshock can be an economical class to compete in but not if you want to ride a works replica special based on something as unlikely as a TL250.

My 10 cents worth for what to include in any proposed UK national rules for twinshock trials bikes: Put an era limit on the bike ie major components of bike must have been manufactured before (say) 1986 Specify which major components are controlled (frame, engine external appearance, forks external appearance) Specify mechanically operated drum brakes and cable operated clutch Specify air cooling Specify twin shocks (not sure about the works OSSA but the idea is to exclude 1985 TY250N Yamaha) Non controlled mods are things which people fiddled with at the time like tanks, seats, mudguards, shockie mounting location, shockie type, exhaust systems, frame chops (steering angle, wheelbase, tubes removed under engines), fork travel Bikes should be able to be bitzas as long as the major components were made within the era or are exact replicas.

I wonder why they spared the engine and tyres from a similar silvery fate?

Sounds pretty likely you have found the problem. While you have it apart, see if you can work out why the washer was like that. Is it possible an impact on the shifter caused the problem?

Mr Clean the XT500/TY hybrid photo posting tells me you've definitely got a pretty wicked sense of humour. I'm beginning to wonder if this whole thing about lightening your TL250 isn't just leading us all on. It hasn't emerged yet why you have chosen the heaviest trials bike sold in that era to lighten as much as possible. Do you enjoy a challenge or is it just a Honda 4 stroke thing? To answer your NEW QUESTION, yes they are completely different bikes. The TLR250 is based on a completely different engine, has a completely different frame and running gear.

I'll assume that you either don't know or that it shifted fine before the big rest. It is possible that the indexing plunger is not holding the shift drum exactly in the right spot. Common causes for this are old gummy gearbox oil on the shift drum and in the plunger cylinder and a drum indexing plunger spring that has relaxed.

What Billy says does make sense but why do you need a battery for the fan? It gets very hot here in OZ and we just leave the motor idling when inspecting sections so the fan runs when needed. Sometimes the motor runs for hours without stopping or problems during summertime (well over 100F) events.

More info needed Neutrals between which gears? Upshifting or downshifting? Does it happen when you shift with the motor stopped? Is the shifter moving back freely after you shift? Is the shifter moving all the way back to the mid position each time? Did it have the problem before the several years rest? Why do you think something is loose in the cases? I suggest you post questions about your 172 in the twinshock or mechanical help forums

No matter what frame you use for a TL250 engine, the height of that long stroke, wet sump motor will always create a centre of gravity/ground clearance compromise that handicaps the bike in comparison with others of that vintage. If you yearn for a Honda 4 stroke twinshock that is light and handles well, a far better better starting point is the humble TL125. With suitable engine work (bore and stroke increases), a different front end and rear suspension mods, these can be made into something that is a much better competition mount than something based on the TL250. Attached is a photo of a TL250 (Jeff Eckert, Queensland, Australia) showing an exhaust that lightens the TL250 without spoiling the beauty of the original styling.

From the wide range of lightening techniques you already mentioned for your TL250, it sounds like you already know what is needed to get the TL down to a nice weight so why are you asking for more ideas? If you did all those things to your TL250, would it really still be a TL250?

This is intended for Beta Rev3 owners. If it hasn't been done since the bike was new, you should: Dissassemble, clean and grease the steering head and swingarm bearings. Remove the shock mounting bolts, clean the bolts and holes and reassemble with antisieze including the OD of the head of the lower bolt. Remove the front vertical frame member screws and apply antisieze on their threads. Remove, antisieze and refit the handlebar cross brace screws. Periodically: Check the rear axle nut is tight. Check all the brake disc screws and sprocket bolts for tightness. About the air filter Replace it if it starts falling apart. Keep a new spare in a dark cool place (the fridge is good). Only clean the filter if it is dirty or the oil is getting dry or is contaminated with water. Air filters are damaged by UV light, heat, residual detergent, incorrect cleaning solvent and the mechanical effects of cleaning and reoiling.

Suggest you go back to whoever told you an RD400 piston will make a TY175 into 200cc and point out that the TY175 (66mm) has a larger bore than an RD400 (64mm) so it would be a small bore TY175 not a big bore. Yes a TY175 made 205cc goes great if done properly but it is not easy or cheap.

Those bars on Martin's 348 are beauties. Yes he is tall. As well as the high bars, the footpegs on his 348 have been lowered. The 348 second from the right has the original bars. I wish someone still made bars with a rise like those.

We finally managed to get these four Australian Cota 348s together and thought it would be nice to share the picture

Hello Cactus Jack. Where in the wide brown land are you?

The sleeve in my bike is made from an early 1980s Suzuki GS1000 sleeve and yes it ends up thin when bored to 72mm but is suitable to be bored to 72.5mm if required. The WR200/DT200 big bore pistons are no longer available here either. I would suggest checking out big-bore kits intended for the Yamaha Blaster Quad if you are serious about making your TY into a 205cc.

More snappy: lighten the flywheel More powerful: source a later model cylinder and head. The TY250B (1975 model 434), C and D model (493 model) TY250s are noticably more powerful than the TY250 (1974 model 434) in standard trim. More powerful: Big bore it to 320cc (DT360 piston, new sleeve, welding and machining). Not cheap but works More powerful: fit an ignition that has an advance curve More powerful: raise the compression ratio More powerful: fit an expansion chamber Talk to Bob Ginder at B&J Racing

Mine uses a piston made to increase the capacity of a DT200 or WR200 to 230cc. I've heard but not tried out a big-bore kit piston made by Wiseco for the Yamaha Blaster Quad. It's not listed in the regular Wiseco catalogue but are made for someone selling the kit for the Blaster. I've also heard that a TY250 piston can be used but this must also require a different conrod because the TY250 piston has a larger gudgeon pin than the TY175. KDX220 pistons are the right diameter but I haven't checked ring locating pin locations or pin to crown height on them. There is much more to it than finding a piston. The cylinder has to be resleeved with a larger diameter sleeve, machine the crankcases to suit the sleeve OD, weld the head and remachine to suit the new bore size and weld the cylinder stud holes up and redrill a smaller size. Shape the head to achieve the correct compression ratio. Find longer studs to reach through the head. Use plain nuts. Make a bigger head gasket. Lighten the piston as much as possible. Rebalance the crank, rod and piston to suit the inevitably heavier piston.