Hello to all, perhaps this was commented in other topic, if it was and know where it is please send me the link!
My yamaha XT600Z 1vj (2ty beacause it was assembled in Brasil), has for the countershaft 4th wheel (21th), the part number 55u-17241-00. I can´t find it anywhere. What I can find to buy also here in Argentina is the gear 3aj-17241-00 that has also 21 th and looks the same....do you know if it has any diference ?
regarding the Cranck shaft, I saw some fretting in the right bearing. Shaft is -0.01-0.02 milimeters under nominal bearing inner diameter is this ok?
Thanks in advance for your comments!!
Regards

JP

Yes it replaces it according to fowlersparts diagrams. I assume it’s a direct replacement. If not you’ll also need the 4th pinion. Just get the one you need first and compare it.
I just bought a set of later 5th gears for mine. I believe they were actually changed so it had to be a pair. As far as I know.
Can’t upload any photos but the only specs for the crankshaft are
Crank width-74.95-75mm
Shaft runout- <0.03mm
Small end free play-0.8mm
Big end side clearance - 0.25-0.75mm
Can’t find any minimum diameter of the shaft in the book. As long as it’s a good fit in the bearing (when it’s all sat in oil). I take it you’re putting new bearings in anyway as it’s apart.

Thanks for your soon answer! 4th pinion code is the same for wheels 55u-17241-00 and 3aj-17241-00, 3rd and 1st wheels are besides this 4th pinion, 3rd wheel shares also the same part number in both motorcycles, 1st wheel has diferent code, even it has the same number of teeth. I don´t know if thikness are different or what. Thanks again!

the 55U and 3AJ gear wheels look very similar but the 3AJ part is slightly longer by 2mm? Gear widths and total gear widths on the transmission shafts are very critical. I would be very wary if fowlers says is a direct replacement. No where else on the net does it say that. The 55U gear wheel was used in later model TT600R transmissions so you may be able to find a second hand one, even if you have to buy the whole TTR transmission.