guy53

I modified the frame of an A model to Majesty spec a few years back. I think that the first thing to do is find a straight frame than build a jig. I'm sure you will find very good advise on this site.

It sure look like an original 434 head with a modification made in an unconventional way. if it work, use it. The original plug wire must be short. Guy

If I remember correctly, Yamaha made a version of the TY 434 to be use on farm i.e. more trail oriented. Does it have the foward footrest ? Guy

Are you in North America?

I've use fiberglass and plastic gard on a dirt track bike without any problem

nice bike

I'm surprise that no one ask: Have you tried any of them? Is there one that you feel better ridding? Guy

I forgot, the chain of a trials bike doesn't very hot when riding, I think that it's the reason why the ATF work for me. Guy

For half of a century, I've used ATF to lube the chain. After a ride I wash the bike than I generously lube with ATF, I wipe of the chain before leaving for the next ride. I found the lightness of the oil penetrate the rollers and push the mud out. Only thing, don't forget to put something under the bike. Guy

I do agree with you Jon v8 that the Mikuni that come '' stock '' on TY are the best and I would never swap one for another make unless the original was worn out and I would not be able to find another original TY Mikuni, but the Mikuni VM are not the ideal replacement for a TY 250 in my opinion. Guy

A few years back, I replace a TK carb on a model 434 by a VM32, I never could make it running well. I'm not saying that I'm a Mikuni engeneer but I know my way around them, if you don't find a rebuld kit, you should consider OKO. The comment are very good. Guy

Are they still avalable ?

1st : FIT !!!!! the rest is up to you Guy

When I use ATF to try to improve a clutch, I change the oil after acouple of hour of riding 2 or 3 times before deciding if I need to change the plates, sometime it work sometime....... Guy

I would check the air filter and exhaust first. Guy