Apr 13, 2007
i just picked up 2 1989 yz125's for free... they both need new top ends i have a piston and rings for one of them but im not quite sure how to go about cleaning out the bottom end.. and the shaft looks to be a lil rusty on the very top but i should be able to clean that up.. the bottom end is still lubed but there looks to be some crud in the bottom end.. maybe run some oil through it ? btw this will be my first bike to work on.. my dad will be helping but any help is appreciated. :)


Sponsoring Member
N. Texas SP
Nov 25, 1999
Not real sure where to start.
The crud is most likely just residue left from the two stroke oil. If the crank moves freely AND within specs, put the top end in and have fun. If you start cleaning it, you will likely need to split the cases and do a very thorough cleaning. If you don't dislodge any of the crud and you are within the specs you should be good to go. Have fun, you'll learn alot about your bike by working on it from the start. Good Luck and come back with questions as you need. Try the search function but don't use model specific questions unless a general question doesn't answer it. Lots and lots of info on top and bottom end work. Most of the info is not model specific, just technique and things to watch out for.

Nevada Sixx

Jan 14, 2000
dont go overbored with restoring a bike that old, i totally redid a 89yz 125 a few years ago and it cost about 2 grand,,and i still had an old bike...better off buying a new one!!!!! by the way, bikebandit.com was a good source for parts of a 89yz,,but some parts i had to get ones from a 90 model as alot of the 89 were hard to find. i'll be glad to try to help you all i can if you have any questions about that 89yz...
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