feetupfun

Not too sure about that statement

Headstock angle looks standard in your photos. Some stampings are quite poor. Here is what you are looking for (photo of a M49 frame headstock)

You have not said if the erratic running is throttle-position dependent or not. Because you have said that first and second gears are OK but not the higher gears, I suspect the problem is that the fuel level in the float bowl is not being sustained under conditions of high demand. This is because when accellerating through the gears, the throttle is usually held open for longer in the higher gears, yet while the bike is idling before you start to ride away, the fuel level is more likely to be able to recover). To check for this you will need to check the flow rate through the whole fuel path ie from tank though tap, hose, in-line filter if fitted, banjo fitting filter and float needle/seat and with the fuel tank cap in place all at the same time. The original fuel taps on Bultacos are notorious for being restrictive but your problem may be anywhere in the system. It would help with the diagnosis if you could work out if your problem is throttle-position dependent. It is possible for an ignition problem to be RPM dependent, but if it was that, you would probably have the problem in all gears.

Yes, YZ125 and IT175 clutch covers from C to F model at least and maybe later fit perfectly on TY175 bottom ends Sorry I don't know if there are any 250 or open class MX, YZ or IT (premix type) clutch covers that fit the TY250 bottom end. I suspect the TY250 bottom end is most similar to the trail/MX motors made from 1968 to 1973 and the production motors of that era had oil pumps.

The triple clamp geometry and steering head axis angle relative to the front downtubes are identical on all twinshock TY250 models. If one of your bikes has the wheel closer to the frame tubes than another bike, there is something non-standard about at least one of the bikes. My first thoughts were that: Are the fork tubes set to the same height in the clamps? Are you measuring with both sets of forks extended the same amount?

I must say I've not heard that sentiment before. Most people I know who have bought Fantic twinshocks have done it because they are one of the easiest bike to win twinshock trials on. I expect next someone will say that it isn't fair to fit Fantic twinshock/Marzocchi forks to a Yamaha twinshock.

If you ask your question here: http://ozvmx.com/community/index.php?board=11.0 you stand a good chance of getting a well-informed answer from Doc

Yes you are right. You are in the wrong forum and probably website as well Yes the sideport exhaust motor will have exhaust pipe issues in the twin-downtube frame - that is why Suzuki changed the frame when they changed the motor design

It would have originally had 428 chain but sprockets are available for either chain size. How accurate do you want the fork travel measurement? They should have something like 7" fork travel

No matter how well set-up a clutch is, the rear wheel will turn if the bike is in gear and the wheel is off the ground. Your not being able to stop the wheel with your hand is not unusual at all as far as clutch drag goes. You will find that the rear brake is very effective at stopping the wheel turning while you are stationary balancing.

I welded a small piece of steel on the upper side of the brake pedal arm so that the lug on the clutch cover continues to be the up-stop. If you are also wanting a neat way to hold the footrest up for starting while retaining the footpeg spring, there is a forum thread showing how. I'll see if I can find it. David Here it is http://www.trials.com.au/content/index.php...r&Itemid=42

I'll have a go Honda plan to reduce production costs. One change will be the reduction in size of operations in Spain Honda will continue to market the 4RT as a Montesa The 4RT will be assembled at a Honda plant in Italy instead of in Spain The Spanish Honda (montesa) plant will cotinue to make plastics and do painting

When new, linings are 3 to 5mm, depending on brand. Depending on how worn the drum is, the cam may go over centre with 2-3mm still left on the linings. I suggest you inspect and measure the drum diameter and measure the OD of the linings with them installed on the backing plate. Also compare the radius of curvature of your linings against the ID of the drum. To work properly ie to touch over the whole surface, the radii should be very close to the same. Many old bikes need the drum resleeved or machined and oversized linings fitted to restore the radii to be the same again.

I had to do that little filing job too but on my 348.

If you are using it for trials competition a BP5ES is ideal. I use BP5ES in my OSSA, Bultaco and Montesa twinshock trials bikes with no issues. If you are doing road riding or energetic trail riding, then go for a cooler plug.

Bogwheel be careful here because your SM frame may be different to a M199 frame regarding the rear suspension geometry. There are plenty of Betors in use here. You may not have recognised them as such though because they are "very similar" looking to Falcons. I have a set on my 348 with 60 lb springs and they are OK on that bike. If you want to try them, I can get them brought to the Conondale trial. David

Which front hub does your 349 have? They came with the 247/348 type front hub, and a front hub made by Honda that is completely different.

High exhaust gas temperature does not mean the motor is running hot If the fan cuts in and out then the mechanical parts of the motor are at the right temperature Serious overheating = coolant loss from the coolant system overpressure relief valve If you are fanatical about knowing how hot the motor is, you can use a hand-held non-contact thermometer (laser guided) on the barrel or head. It should not go above about 100 degrees C. These bikes are fine here in Summer (Australia) and it gets just as hot here as it does in China. If the bikes's cooling system is working correctly, the rider will fail long before the bike overheats. David

The engine and frame numbers would be helpful for ID The shape of the bike is quite distorted probably by the camera or reshaping of the photo so it is hard to tell if the frame has been chopped. Forks rake appears very steep. Paint scheme is mostly 1975 KT250A1 I'm assuming MD is in the US Value depends a lot on mechanical condition

You have done things that will increase the temperature of the exhaust gases Rings bedding in (friction) Reduced compression (less efficient combustion) If you have leaned off the carburetion, that will also increase the exhaust gas temp The exhaust smoke was probably due to oily deposits within the exhaust system being vapourised by the higher exhaust gas temperature. The deposits were deposited when the motor ran cooler prior to your engine work. Once they are burned out with use, the smokiness of the exhaust should return to previous levels (assuming you haven't changed oil type or mixing ratio) Using hylomar on the head gaskets will not cause exhaust smoke Oil put on the rings for reassembly would have caused slightly more smoke than a normal cold start for a few seconds The discolouration of the exhaust can probably be polished off if it worries you

A likely cause would be too much air getting to the motor with the throttle closed (air leaking into motor).

Thanks PA - it looks suspiciously like stationary balancing to me

Yeah man that's easy. Hang on a minute - whats a Track Stand?

I just measured my TY175 and TY250 twinshock forks and found that they are the same length, not 20mm different as I had thought.

This is about your 2mm ring gap comment If the old piston has a ring end setup like the MAR piston, the standard ring end gap is huge as measured by putting the ring in the bore, because the locating pin separates the ends of the ring while most bikes the pin sits within a recess in the ends of the ring.