jse

Probably not costly. My guess is that the shift centering spring needs adjustment. It's under the clutch basket. Jon

Quite true. Honda, for instance, used double wall head pipes for many years before that. From what I was told, it served two purposes, to keep the outer chrome from blueing and for looks as the small pipes did not look as good to riders even though they were more effecient. On the 4RT, they just use the small diameter pipe tuned for that particular engine as that's what works even though it looks kinda funny. Jon Step away from the bucket, Billy, and nobody gets hurt............

I have a friend who is a Mechanical Engineer and runs a thermo-wrap on the head pipe of his Trials bike. I imagine that other than the frying-lower-leg-skin avoidance feature, the effect is probably minimal at low RPMs/fluctuating pressures in the pipe. Due to the operating conditions of a Trials engine, you also need to worry about rust and the mud stained appearance is usually not so good after a time. On road race, narrow RPM, consistant load engines I think it works well, reducing radiant heat and keeping gas velocity high. Jon

Now three old farts, but not the one who can't figure how to shut off the Caps Lock............ Jon #3

Most auto supply stores have sheets of gasket material that work fine. I buy sheets of various materials to have for emergencies and keep them in my trailer. The gaskets sheets are usually near the sealers, epoxy etc. area. Judging by the large radius at the squish band/chamber area, the insert should smooth out the throttle response well. If you can't find any material for the reedcage gasket, let me know and I'll send you one. Jon Forgot to mention, use the thickest material they have.

Thanks, Chris! I have a lot of fun writing those articles and besides, at my age I have to pass on all the stuff I've learned before I croak.... My advice as to closed throttle is just based on the design of the enrichening circuit. I also agree with you that an open throttle may also work and the best way is to try both techniques to see what works best. The PWK is a different animal from the Dellorto and the concave design of the slide would make the open throttle technique work with the PWK but probably not be as successful with the round slide Dellorto when I think about it. Cheers! Jon

Doh! You're right....brain fade, forgot it was a Raga. I would be surprized if the KTM 300 runs the PWK 28, it's more likely a PWK 39. He may have to order some jets for you as the 28 takes much smaller jets than the 39, which usually runs a main in the area of #175. I have some jets possibly and will check my jetting kit and let you know. Take a jet inventory (or "map" as it's called) when you clean and check the carb so we have a start. Main, pilot, needle, needle jet etc. The float arms will be parallel to the sealing surface of the cab body to be at the correct float level, with the carb held so the float arm assembly just touches the float valve pin. The enrichening circuit usually works well without modification in the Keihin, just don't open the throttle when kicking at first. Jon

The Dellorto's usually come with a #60 or #70 starter jet. I find that changing the SJ to a #80 (or drilling the SJ out to .031" like I did) made my Pro usually start 2nd kick, in any weather, frying to freezing. Jon

Be sure to pack the bearing with grease before installing. Check the torque setting on the rear axle, they are often over-tightened and this exerts excess side loads on the races. Jon

Try a little "practice" with the in/lb wrench with a capscrew in a nut in a workbench vice and that will give you the "feel" for what 108 in/lb torque setting will be on the ones that are difficult to reach. See you on the 28th. Jon

You may have a stock #35 pilot, try changing to a #38 before engine work. Jon

They are obviously on the Internet already and what is it about search engine and "free download" they don't understand?..... Jon

Do them "snug" as evenly as possible, run it a bit and re-check. The capscrews only go to about 9 ft lbs or 108 in lbs and chances are you don't have a torque wrench that reads accurately at that low a level. I've never had a problem with "snug", but I re-check them after a heat cycle or two and now and then when servicing the bike. The copper washers will compress over time with heat cycling but just check them once in a while and you will probably never have a problem with head o-rings going out. Remember to always grease o-rings before installation, including the one at the top of the chamber insert. They need to be able to move around slightly to "settle in" during installation, otherwise they can be damaged. Jon Forgot to mention, try lowering the needle clip before going to the low compression insert (unless you want to soften the response) to see if that solves the pinging.

The kickstart issue is not new. It was not unusual for riders to snap the forged steel kickstart lever on TY350 Yamahas. The 350 was based on the big-bore MX engine with massive crank weights and flywheel, which also had a large steel band attached. Riders would jab at the levers and all that mass would resist turning and the lever would bear the brunt. Trials engines are quite different to start than the "normal" off-road engine due to overcoming the extra mass attached to the crank. I tell riders to start the bike like a Harley, don't jab at the lever, engage and use body weight to get things moving. We love the light weight bikes but they don't take kindly to misuse. Jon

That is my Shoei I had for my blue JTR370, all my relatives liked it too.... I've never had a problem with the stock steering bearings, but I service them now and then. I'm guessing that greasing and adjusting steering bearings is one of the last things on most riders minds and they only notice them when they fail from lack of attention. I saw the crossreference for several other bearing brands but nothing came up for the SKF other than 100Cr6. Jon

No. Jon

Got a new set out and "32004X" seems to be the standard size, no other markings. Jon

Bill, If you are just messing around the property or riding a local Trial the SF should work fine. I run a large body SA I got from RYP and made a vibration-proof mounting system. It looks clunky but is essentially non-restrictive and works a treat up at the ultra high altitudes we run at the Ute Cup. Jon

Usually only come as a kit with new pucks. Jon

If you do any hillclimbing or high-altitude extended fairly hard riding, I would avoid the small clip on spark arrestors that have the outlet hole smaller than the ID of the muffler spigot. It's my experience that they tend to restrict the exhaust under severe loading and cause overheating. At the Ute Cup last year (8K-13K altitude) just about all, except one, of the plastic end cap mufflers used on the new Pros lost the end spigot due to the plastic melting at the end of the plastic cap. All ran the small add-on SA with the smaller ID outlet. I would imagine they are fine for a "normal" riding scenario, but under more severe conditions they are too restrictive. Jon

These mods were done over 20+ years ago and still work fine. Angling the tip and securing the ferrule takes the slop out of the cable allowing for a "normal" setting of the lever throw. Next time you get a chance, pull on the TY lever and most likely you'll notice the ferrule wiggle at the lower mount, it's surprizing how much it affects the engagement. I know the aftermarket machined extender you mentioned and just about everybody used them. Unless you are restoring a collector's bike and want it absolutely stock, if you are going to ride the bike it's some mods to consider. I've had the bike since new and ride it non-comp just for fun as there are no classes for it. It's not a twin-shock and it's not modern. It's still fun to ride but it does make me appreciate my Magnesium engined 147 Lb Pro.I think the classification for the TY350 is "Modern Classic"..... Jon

Bill, I'd repack the silencer. You can then clean the perforated core which will help engine response and smoothness. Oval core silencers are a pain to re-pack with sheet packing but a loose type packing, like SilentSport, makes it much easier. Be sure to read the directions carefully, the loose packings perform better if not packed too tight. Jon

I extended mine 10mm. You'll need to pull the clutch pressure plate to pull the rod out slightly so the lever shaft will clear and it should just come out. Three other things helped: replace the cable internal with woven aircraft control wire and thread the end of the outer cable ferrule at the bottom end and use a nut to cinch it up where it goes through the holder on the left, rear cylinder stud (see photo). This will keep the ferrule/housing from flexing and makes the clutch action more "direct" feeling. You'll also notice that I canted the very tip a little to the left so it has a more direct pull. My TY is a one-finger pull and feels very smooth. Jon

This is true. In the "old days" I would "read" the color (and hopefully not the ash) of the piston under the crown to set the jetting on certain of the two-stroke roadracers. It was a much better indicator of sustained chamber temps than the crown color. The crown edges and the outside of the squish band in the head is where you looked for signs of detonation precursers. Jon ps. I run, full-synthetic 70/1 in my Pro and 50/1 in my air-cooled TYs, the TYs a little more prone to cylinder distortion and hot spots due to the lack of liquid cooling. I've never had an oil-related engine failure with my Trials bikes in 41 years so my ratio guessing seems to work for my bikes and riding style (or lack thereof.....). The ratios chosen on the basis of many hundreds of engine innards I've inspected and the advice of a bunch of chemical and mechanical engineers I've talked with who replied to the question if those are good ratios to run, with "yep, sounds good to me"........

Take the rear wheel off. There should usually be two long wire clips at the top of the caliper that go through the two top holes of the pads to hold them in. When you look at the retaining clips you'll see how they should come out, usually just pulling them will work. The pads will just fall out. Put the two new ones in and re-install the clips, lever the pads apart a little with a large screwdriver (so the disc will fit in) and put the wheel back on. They may need a short break-in time to grip well so expect them to be slightly "weak" at first. Jon