donmurray

Had the same problem with a 2003. Decided to forget anything that looked like a halfway fix. 1. New standard clutch plates. Cork and paper. The mix of material helps the engagement to be more progressive. Insert them in the proper order (ask the supplier). 2. Sanded the steel plates with a crosshatch pattern with something about 400 grit. 3. Use oil recommended by the manual. It was ELF, but don't remember the exact spec on that. Clutch worked perfect. Zero drag and nice progressive engagement. Depending on rider and conditions, these clutches are worked hard, so they may only be good for a year or two. Any 315 that's been rode hard and put away wet will probably need a clutch rebuild.

I got significant improvement by replacing the 3 stock inner fibre plates with BJ plates. The BJ plates may be too abrasive for the outer alloy clutch parts. I kept the stock steel plates and just put a cross hatch pattern on'em with some medium grit paper. Changed nothing else and the engagement was more progressive. My 125 is a later model that already had the hydraulic setup, but not the longer arm.

http://www.progoldmfr.com/products/chainlube.html Great stuff. Goes on thin, but dries overnight to leave a dry lube coating. I recoat when the chain starts looking really shiny. No sticky, greasy mess to pickup dirt. I think gease or oil lube on a dirt bike chain become grinding paste as soon as it picks up some dirt.

Thousands of an inch. .08 means 8 thousands. Sorry, but here in the backwards USA we still use that system a lot.

Can't help with torque numbers. No oil filter on mine, but there is a wire screen located inside the right enging cover. If you want to clean this, be sure to have a new gasket on hand. The old one was stuck hard. Probably not necessar to clean this very often as it would only catch good sized pieces. Like when there was some hard transmission usage, or bad engine wear/failure. With no filter, it's a good idea to change the oil often, and right after a good warm run. This removes suspended particles. Valve clearance Cold= 0.08-0.12 inlet, 0.10-0.14 exh. Screw and locknut adjusted. Make sure you're on top dead center of the power stroke when adjusting. I use a small round wood rod or piece of wire in the spark plug hole to check for tdc. Put it in top gear, rear wheel off the ground, and bump the wheel to make small movements in engine.

Don't fool around with unusual solutions, when a new the stock clutch works OK. Replace all cork, fibre, and steel plates with a new standard plate set. Change the oil to exactly what the manual specifies. It will disengage fine and have a progressive feel. Install the cork and fibre plates in the correct order. You could put a cross hatch pattern on the steel plates with some 400 grit emory cloth. That will make them retain oil film better.

The rear tread knob squares usually wear down more on the front part of the knob. If you reverse the tires there will be a sharper point on the front side of the knob, and a down taper on the back side. Should grip better.

A comment on the rich condition being discussed. I've done some thinking about adapting modern 4T engines to the unique demands of trials. One of the problems is that a 4T engine can be easily stalled at low rpm if the throttle is quickly opened wide. Maybe the mfgs are trying to prevent this with a max rich mixture. This would reduce the instant lean that occurs when fuel cannot respond as quickly as air. Not a big problem when the rpms are up, but in thump mode just one gulp of lean mixture can be a big surprise. You get drag when you expected thrust. When you wack the throttle on a 2T engine there's a fresh, correct ratio, mixture just waiting in the crankcase. 4T engines may need to use a computer controlled throttle, or direct injection to make them more stall proof. You would think injection in the port near the valve would handle it. From a 4T lover

Same happened on my 125F. I took all the original paint off and resprayed with some high temp exhaust paint from an auto store. It still peeled off from the first few inches. I'm sure there's a paint that will hold. Maybe somone will post.

I filed down a long wood stick until the end fit the square hole inside the tube. Used this stick to keep it from turning while I tightened the outside bottum nut. Make sure the threads at the bottom are clean and lubed with a little light oil so it tightens easy.

Probably oily carbon buildup. It's hard to remove and clean, so many of them may have never been cleaned. I tried soaking mine in a small tub of diesel with some fuel system cleaner added. Left it in there for a couple of days, but not much came loose. Next I suspended the expansion chamber vertically from a piece of pipe set across two saw horses, and set it afire. Just held a propane torch under it aimed at the bottom opening until smoke was pouring out. It would have a little flame inside and smoke would come out the top end. I would then turn off the torch and let'r smoke for a bit. When the smoking decresed, set the torch back to the bottom again. I did this from both ends until it would not smoke anymore. Tapped it some to get any loose stuff out. BTW, the diesel soak may have saturated the carbon buildup and helped the burnout procedure. A little warning. If you let the flame inside get too big or burn too long, it may get too hot and melt some aluminum. I think there's a type of cleaning dip that could be used. One that will not harm aluminum. Like those 5 gal buckets of carb cleaner. If you can find a radiator shop or such that has that type of cleaner it would be a lot less trouble.

Austini, How much did you extend the clutch arm, and was it hard to remove?

Can't help you with the sub frame, but had to let you know that in 1959 I purchased new one of the 250 500cc English made Enfields that Indian rebranded. It was called the "Woodsman". Had a high pipe, alloy fenders, and higher final drive ratio. It was my only transportation, but I also used it for enduros, and scrambles (motocross). Rode it hard for 2 years, and 17K miles. Wish I still had it, but that's a common story.

Found a US source. http://www.sprocketspecialists.com/ It was listed in their catalog under Yamaha TTR125.

Where did you get the 10T sprocket. Can't find one in the US. Don't understand what you mean by extending the clutch actuator arm. Really like my 125F long ride. Plenty of power for a low skill rider. FYI. Mine came with a 105 main and a needle that is not adjustable, so they may have changed standard jetting recently. If you're going to change/check the jets, get a new float gasket. They're hard to save. I sanded the steel clutch plates, and replaced 3 middle fibre plates with ones from a US company called B&J. More progressive engagement.

Anyone know of a source for a 10 tooth front sprocket. I've tried The Tryals Shop, and Sprocket Specialist in the US.

Use the highest gear you can and still have enough power. Lower rpm is suposed to produce better grip because the longer pause between power pulses lets the tire regrip. Static friction is harder to overcome than dynamic friction. Another way it was explained is: If a loaded cardboard box is sitting on the floor, it takes more effort to start the box sliding than to keep it sliding. Use a new tire or reverse the old one so the knob edges are sharper, or you could shave the knobs so the forward side is shorter than the back (griping) side.

Americans like motorsports that exibit power, close racing, and a little violence. Motorsports that emphasis technical and driver sophistication don't do as well.

Looks like trials keeps moving further from any normal form of motorcycling. There's some very impressive esoteric riding, but it may be appealing to a smaller and smaller group. It's more like motobatics. Too much stuff that's totally removed from bike riding. The hopping looks a little silly. Other ideas that would get the sport closer to something all riders can relate to: 1. A min weight limit that's just a little less than the average trail bike. 2. A required seat at a min height 3. Min tank capacity 4. Four strokes only. 5. Some small point reduction (negative points?) for quicker times, and keep sections tight to reduce risk. 6. Points for hopping and stopping Just make them start and RIDE through a section.

FYI and opinions on a new TY-S125F My new Long Ride came with a 105 main jet which may be fine. It did have a 15 pilot jet instead of the preferred 17.5. If you order new jets, order a new float bowl gasket also. The bowl and gasket can be stuck hard and it's difficult to save the old gasket. I had to tap a thin sharp object between the bowl and body to get it separated. The idle mixture screw is very difficult to get to. You have to move some cables out of the way to see it. From the right side you can get a very short/shortened driver in there, but one of those 90 degree geared drivers is best. Perhaps a driver bit for a small rachet handle would work. Mine came with the Magura hydraulic clutch, but the clutch is not progressive enough for a clutzy rider. Has anyone experimented with one of the synthetic oils that have friction modifiers? I know they are not recommended for bike clutches, but I wonder if the slicker oil might soften the clutch latch point. I plan to install a slow throttle spool and a 10 tooth sprocket so I'm less dependant on clutch work for slow stuff. The head pipe paint was not high temp stuff, and the first 200mm melted instantly on startup. Starter crank hits the brake pedal at the bottom of its stroke. Some careful work with a small hand held grinder can shape the bottom of the brake lever to conform with the starter crank shape. Position, mark, grind, repeat until I finally got more clearance. They still touch, but no real hard contact. The rear tire is not tubless. Could be vulnerable to tube pinching if riding with low pressure over hard stuff. The seat is low but still useful for old guys or weak legs. Runs a long time on a tank of gas. Fun bike to ride. I like the sound and feel of the 4 stroke engine. This might be the ultimate play bike. The engine does not have the snap of a good 2 stroke trials bike, so if you want power for a hard launch or a long steep climb it may not be the best choice.

Anyone know the Mikuni part # or jet type codes for the 102.5 mainjet, 17.5 pilot jet ?

On my Montesa 315 I thougt the only useful purpose of the front chain guard was to keep toes, or other body parts, out.

My 02 has a 35 pilot jet, 110 main jet, D37 needle at 2nd from bot slot. No flat spots in throttle response and no hesitation. Don Murray

Thanks Mostar, May just try that. I was planning on using the Krylon Fusion paint that's supposed to bond well with plastic, but I'm not sure how it will stick to the orginal paint. May be easier to sand a little and not use the Fusion stuff. What kind of paint did you use?

Anyone know an easy way to remove the paint from a 315 tank? I'm afraid to try any of the usual paint removers on a plastic tank.