Sorry about forgetting to add the website link to the oem parts place I use, meant to have it in my post to look at the part numbers. 1984 XT600L Yamaha Motorcycle Parts

The one problem with the plated TT cylinder is once it is worn, it is done. You can bore it out and have it replated, but they are never as good as the original factory, I think it has to do with oil penetrated into the walls and the plating then flakes easier. As long as it is within spec the TT should be good, they do wear a little longer than the non plated.

Anyway, since the gears are the same #'s and the bearing are different I think they just used a different bearing in the TT (but why?) so that corresponds back to the axle assembly # needing to be changed slightly, I would bet the axles are interchangeable. Gearing commanders # must be wrong or they are comparing the XT/TT550 and the 600's. Anyone have a factory TT service manual to see what the ratio truly are? Also I see it has '89 XT, it's possible the '88-'89 has changed there also, these years have several differences to the '84-'87 years.

EDIT: I see the bearing that has different numbers between the XT and TT are actually the same trade number, so the physical dimensions are the same, it is the seal or seals that was changed, maybe they used a bearing that had 1 seal and the XT had none or 2 ect... have to look into why it was changed.


I did see the '84XT part breakdown, there is 2 carb assembly numbers, 1 for 49 states(and the rest of the world), 1 for California(leaner jetting only diff., third series of numbers is changed to 01, it shows the third series change to the standard part.

Momentum is indeed the other reason for the heavier flywheel, and for kicking it would again be nice to know just how much a difference it makes.