feetupfun

Hi James I suggest you might get more response if you post your 349 queries in the twinshock forum. I would say it is very likely that the 248 front end would fit your 349 provided you use an axle length and wheel that matches the width of the fork tube spacing of whatever clamps you use. David

Mich Lin Are you having a bit of a lend here? Do you really carry a handgun when out riding? Where I ride we have snakes that leave anything in the "Wild West" of the USA far behind for danger to humans (Australian taipans, eastern browns, and tiger snakes in particular are quite deadly while death adders provide a similar risk of death from a bite to the US rattlesnake) yet all most people do is keep their eyes open. People who like to take precautions carry constricting bandages and some form of hand held communications. Please tell me the snake shot gun thing is really a joke.

2001 Rev 3 270 should have come from Beta with a hydraulic clutch. Betas have had hydraulic clutches standard in all Rev 3 and also the preceeding series which came out first in 1994 (Beta Techno). Are you able to post or email a photo of the bike you are looking to buy?

Mate those forks must be pretty confused with all that swapping around. The forks with the Bultaco sliders should work well with 190ml per leg and so should the ones with the OSSA Betor sliders. If you are ever in doubt, just use the measurement method with the forks bottomed with springs removed. Add oil slowly until it is about 5" from the top of the tubes. As a check, extend the forks with the springs out and caps off and if they snore near the bottom, you need more oil. Fork setup is such a personal thing that I am reluctant to suggest oil weight and spring preload for you but seeing I am also 14 stone of rippling flab you may find my numbers are a suitable starting spot. 75mm of preload with straight wound trials rate springs and 7.5WT oil works pretty well for me in my M49 Sherpa T and MAR OSSA. 10WT is a bit heavy unless you like a slow fork action.

I suggest you ride a few other 349s and compare. The clutch on the 349 and 348 is probably the worst aspect of those bikes for modern trials riding techniques. The drag should be livable but it should not slip. Sometimes slip combined with drag can mean plates that are not flat. Slip combined with drag can also be caused by the springs exerting uneven pressure on the pressure plate. After lots of work, my 348 clutch disengages nicely and doesn't slip, but engagement is still difficult to control in tight turns. It really is a good bike for non-stop events!

With Rev 3s, the riding duration is highly variable depending on how much fuel goes out the float bowl overflow. If you have yours sorted, and have a clean air filter and good jetting, it should do more than 20 miles of steady gentle trail riding on a tankful. That 20 miles would take about 3 hours to cover in the sort of terrain I'm talking about.

The aluminium tanks fitted to the TY250 models after the A model are pretty much the same capacity as the steel A model tank. If it's important that the volume be known, I could accurately measure the capacity of an aluminium TY250 tank. The aluminium tanks are definitely lighter than the steel.

If you don't have enough oil in your fuel, the friction from the rings and piston rubbing against the bore greatly increases. This friction can get the rings and bore and piston very hot. Aluminium expands more with temperature rise than steel and cast iron so as your bits get very hot, the clearance between the piston and the bore becomes too small. If this process goes far enough the parts may stick (sieze) together. Even if they don't get to the point of seizing, running an engine with insufficient oil will make the rubbing bits wear out faster than otherwise. The heating due to rubbing friction has nothing to do with the heat produced when fuel is burned in the engine. The amount of oil in your fuel has only a tiny effect on the amount of heat produced by combustion.

I put lightweight all plastic acerbis hand guards on a trials bike but took them off after one ride because they made the steering feel noticably heavier in the tight bits. I was trying them out after having problems on an exploration ride with the lever knobs catching on vines and branches.

Yes it is a common problem with tubeless fronts on tube type rims.

How can you tell that the knock happens at the top of the piston's travel?

I've had another look at the TY175 engine number/year of manufacture chart and on closer look it appears to be attributed to Australian TY175 researcher Stephen Fox rather than to John Cane. The chart indicates that based on your engine number the bike was made in 1979.

Yes Stuart, I can do photos of the M49. At the moment it is pretty ugly with black frame and paint being stripped from tank and sidecovers. Is there some particular feature that you want to see? Mine is also very early M49000100. Let me know what you want to see and I'll send them to your PM box or email. David

I tried riding the bike with the old Firestone front tyre and by the feel of it I reckon the air might have been from another planet because that is what the steering felt like. Unfortunately I suspect the air was not from such well regarded Trials riding areas as the rocky dry Spain or slippery Yorkshire because it was contained in a tube that was marked "made in Thailand" and so probably was inflated by the previous Aussie owner with nice clean Aussie air.

The oil ratio you use depends on what you use your bike for and the conditions under which you ride it. For trials work (in sections) the engine doesn't need much oil in the petrol. If however you are going to use your bike to ride along a beach in soft sand, or to cruise up the highway at 100km/h, or to climb mountains that require lots of open throttle work, it is prudent to use more oil in your fuel. As well as the type of riding, it also depends on how hot the air is where you ride and if you ride with mud on the fins. Where I ride it gets extremely hot in summer and some bikes just stop running due to fuel vapourisation problems. You can hear the fuel boiling in the carby. Higher engine temperature usage should be matched with more oil per unit of petrol. What one person gets away with in their riding conditions may bring on high wear rates and maybe even seizures in another person's riding conditions.

I just took a very old front trials tyre off a recently acquired M49 Sherpa and thought it felt a bit heavy. It is a Firestone made in Spain with vee pattern blocks and is worn down to about 3mm block height. The worn out old Firestone weighs 4765 grams while the slightly worn 2003 tube-type Michelin that went onto the bike weighs 3506 grams. For non-metric people that is a weight difference of more than 2.5 pounds. I hate to think what an unworn Firestone would weigh. The sidewall of the Firestone has a little brag label saying "gum dipped" which I guess was a pretty cool thing at the time. I can't bear to throw it away as it is a terrific reminder of how much tyres have improved since 1970.

If you want the best shock action, buy Falcon. If you want to keep to a tight budget, buy NJB.

Ok I've found a reference chart for TY175 engine numbers vs model and year attributed to John Cane and printed in VMX magazine issue 18. I'm not going to spend half an hour typing it out but here is what you will need to post or PM to me if you want a dating for your TY175: If it starts with 525, the first two digits after the 525 If it starts with 1N4, the first digit after the 1N4 If it starts with 1R1, thats enough. If it has a different prefix to those above, it may have started out as a TY125.

For a manual, watch eBay. One will come up. A good starting point is: 6psi front 4psi rear No you wont hurt the sidewalls unless you smash the rim into something hard at speed in which case yes you will cut through the sidewalls and tube. If you ride at high speed in warm conditions you might overheat the tyres so if you do much road work, you may need to pump them up for that use. It is impossible to find decent grip off road with trials tyres at tyre pressures much above what I have recommended. Many newcomers are worried about getting flat tyres when using trials pressure so you are not alone. David

Yes it is OK and an economical option to have the silencer patched. It's a common sight on pinkys. Yes there is not much tyre clearance on the pinky. If the rim is true, the problem may be that the tyre has sat parked in one spot for a while. Pump it up to 20psi until you are ready to ride it. That will help a bit. Then riding it at normal trials pressure should get rid of the rest of the lump in the tyre quite quickly. If you have some way of warming the tyre before riding the bike it will recover shape quicker. If the rim is out too much, you may be able to get it straight using spoke adjustment. A few mm run out is usually OK on a trials bike unless you are going to ride it fast on a road. If the spoke threads are frozen, you may need to replace some or all of the spokes (about $100 for a set of spokes for one wheel). Put some penetrating oil on the spoke threads now if you want to try and adjust your spokes. It is normal for spoke threads to sieze up within a few years from new unless they have been treated with antisieze early on. Have a good look at where the tyre fits to the rim and see if it is evenly seated on the rim. Some tubeless tyres (Dunlop especially) won't stay in position on rims like your pinky so one part of the bead stays in a bit. This also causes the tyre to appear uneven when rotated. Your bike really should have a tube type tyre if you want it to fit properly and easily. If it is a Dunlop rear it is a tubeless type. Michelin make tube type and tubeless type. A Michelin X11 tubeless will probably be OK on your rim if you can't get a Michelin tube type.

There should be three digits at the start. That will determine the type of TY175. If it is the type that has the stand on the swingarm, it will be 525. If it is one of the models made to meet road rego requirements in some countries it might start with 1N4 or another set of three digits. The digits after the hyphen tell you when it was made which is of very little importance generally as all the bikes with the 525 prefix are mechanically identical no matter when they were made. I don't have the reference for the second set of numbers handy. If no one else posts it in the meantime, I will look it up and do another posting tonight. What is the thing about not wanting to post the engine number?

Yes welding and lots of machine shop work are required. Yes it's quite expensive. If you have to pay someone to do the work it would cost probably more than most people would be prepared to pay for a whole TY175 in good condition. The worth of it to you depends on how you value engine performance. They go just like you would expect a TY175 that was made to 205cc ie it has about 17% more torque at the same RPM.

To answer your question about the age of the TY175, yes the engine number is a good place to start. What is it?

Is Bioethanol actually ethanol or is it car fuel which contains some (5% to 20%) ethanol? I wouldn't recommend either for a two stroke trials bike. If it is 100% ethanol you would need to radically rejet your carby to suit it and drain the fuel system and replace it with petrol each time you stop riding (to prevent corrosion of the fuel system). If it is car fuel containing some ethanol, it will still absorb water from the atmosphere into your (vented) bike fuel system but less than if pure ethanol. The wet ethanol would give problems with corrosion within the bike fuel system. Modern cars have sealed fuel systems so usually avoid this problem. The trials bike with a carburettor would also need to be rejetted to suit the different fuel, if you want to retain smooth running. Again modern cars usually have fuel injection which avoids problems with the minor change in fuel properties.

Thanks Terry. It sounds like yours is the first model TY250 which some call TY250A. The cylinder porting and a few other less important motor internals on these is different to the later TY250 twinshock motors. A standard TY250B and later TY250 twinshock motor will pull noticably harder at low to mid RPM than the first TY250 due to their improved porting. The other changes between the first TY250 and later models is that the later ones have a lighter conrod, lighter(mass)clutch and a heavier flywheel weight. This means that one option for you for more grunt is to get the barrel and head from or fit a whole motor from a later model TY250. Another option for more grunt is to big bore your motor to 320cc which requires a bigger cylinder sleeve and piston, the head welded and machined and the crankcases machined to suit the sleeve. You may also need to raise the cylinder with a barrel spacer if the piston you use has a lower gudgeon pin location. Another option for better low RPM power is to fit boyesen reeds and a reed case spacer. An option for more power in the midrange is to have a specially designed expansion chamber and muffler made up to replace the standard exhaust. I suggest that you have a ride of an unmodified B or later model TY250 before you decide on a course of action.