feetupfun

The shape and location of the AB and DE airboxes is the same, but the lids are slightly different because the CD models breathe through a slot in the lid. Nothing that will cause a problem with the seat screws.

It's not raining so I can get to my shed and take photos These are photos of later model TY250 frames showing the seat mounting lugs. The photo showing the RH side of a frame is of a D model and the one showing the LH side seat mount is of a C model. The inner surfaces of the lugs are flush with the inner edges of the frame tubing

yes but you will need to add seat mounting lugs to the A model frame. I can do a photo if you want

I'd like to use Greg's top picture to show people what normal 1970s handlebars look like when they tell me that mine look like ape hangers

It looks like a YZ or IT Yamaha to me. See if you can get a photo that shows more of shape of the hub (between the spoke flanges) and another that shows the backing plate.

Bondy if you post photos of the rear wheel someone might be able to tell you wnat bike it is from so you can easily source a sprocket

Very nice job. I especially like the rubber slipper for the lower chain run

Yes

Unless the nut rubs on the cover you don't need to do anything as there is no problem

Old geezers can have problems getting their boot high enough to kick start some twinshocks. I can get my boot high enough even for my Cota 348, but then it takes such a big hummmph to kick it, it seems to be the hardest part of riding a trial on it. I think JonV8's electric start twinshock has a lot of merit for that reason. As far as standard bikes go, my least tiring bike to kick start and compete on is my M49 (250cc) Bultaco. It is very relaxing to ride and I guess because it is so old, it has somehow learned how to ride.

maybe that one has been turned down - it might explain why it is so clean too

This might sound strange but have you tried the damping with them up the other way? Some shocks have damping that only works with the shock one way up

The standard nut does stick out past the flywheel, but yours appears to be sticking out a bit more than normal. It might be sometning as simple as there being too many washers behind it, or the nut may be longer than the original, or it may be standard and your photo makes it hard to judge exactly how far it is sticking out. It has to stick out somewhat, or you wouldn't be able to get a standard-walled socket on the hex. The flywheel appears to be much better-looking than the usual Bultaco flywheels I see which has me wondering if it is a non-original flywheel

I just thought of something else. Some people just call them "triples", which can get mixed up with another "triples" (three jumps in a row on an MX track)

Despite being a colonial, I don't know where the term "triple trees" comes from. I call them "triple clamps" because each "yoke" has three clamps (for clamping the two fork tubes and the one steering stem) I find the alternate spelling often used for "yokes" quite amusing ("yolks")

Roughness of the race will definitely cause you grief. I hope you know for about $50 you can buy a full set of tapered needle roller bearings, or if you are an originality-is-important type person, you can still buy the standard Yamaha races and use loose balls for about $80.

Yes it works but it is not by flooding the engine. It is by the fuel moving to the "top" of the float bowl, away from where the jets normall suck it from - so it just instantly runs out of fuel

The reason it gets tighter when you fit the top bolt is that there is a small amount of axial clearance in the threads of the stem and the castellated nut, so when you tighten the top bolt, the castellated nut moves downwards slightly, which tightens the clearance on the ball races. I find I have to set the castellated nut slightly loose so that when I tighten the top bolt it ends up perfect. Sometimes it takes a couple of goes to get it right. I suggest you leave the stem clamp bolt and the tube clamp bolts on the top triple clamp loose until you have got the top bolt tight and the castellated nut set in the right spot.

Even if a carb does not ice up, in conditions of high Relative Humidity, the water that condenses out of the air as it goes through the venturi can cause havoc. Have even seen problems with this in the balmy climes here when riding in just after a summer thunderstorm.

You can add a piece to a chain to suit different sprocket sizes, swingarm length etc. Using the rear axle slot would also make the rear suspension a lot softer if you used the same shocks as for the front slot.

may also have been to make it a better flat tracker. It wouldn't be the first TL250 to be used for that

I haven't pulled a Cota 200 apart so don't know the answer. Surely it is no big deal to work out what to do as the sides come apart and support the motor with the side down that you want the bits to stay in.

I used a piece of thin-walled rubber hose as a sleeve when I fitted a KT250 Mikuni to my 348

heat the outside of the case around the main bearing you want to come out of the casing. Use discretion to avoid overheating the aluminium. You are aiming for about 150 to 180 degrees celsius

I have a M49 (1968 model) with those tapered top forks and I can't tell any difference between the quality of the fork action of the M49 forks and M198 forks on an M198. The later type top triple clamp does make it easier to remove the tubes though. The later type (curved downwards) lower clamp is meant to provide reduced fork flex but I don't think many people would be able to tell the difference when riding. From memory of when I had both sets of forks apart, the damper rod assemblies looked the same.