Looks like I will be splitting the cases,advice please!

my 1980 yz100 has a cracked case from the chain comeing off.I tried to go the easy way and sell the bike,:thumbsup: but I cant get the $500 I was looking for.I know thats a little high but the engine only has maybe 2 hours on it top and bottom and everything else is new or looks new.this will be my first time splitting cases so any adivce would help.the crack is in the left side case.how far will I have to tear it down? will the crank have to come out?any special tools I will need?should I be scared?I do have a clymer manual that should be here tomorrow.

You will have to completly dissisamble the engine, to isolate the left case. There are several specal tools for the job but you can ussually make do without buy You will need a puller for the flywheel. Whats your plan for repair, replacement or welding. If the crack is minor you could fill it with metal epoxy without dissisambling.

Check out the video at Rocky Mountain ATV (linked here somewhere)....it shows you step by step how to crack the cases.

Best bet would be if you could borrow the case cracking puller tool they demonstrate. I have one, but unless you're north of Toronto, I can't help ya! ;-)

I agree with the suggestion to use the rocky mountain videos. There are three parts to the "bottom end rebuild" and it is a very helpful tutorial.

Part 1:

part 2:

part 3:

have you tried j.b weld?

Thanks for the advice,the video's are a great help.the crack is top to bottom,I tried jb weld but it only held up for one ride and the crack came back.I got a complete case off ebay.this will be my first time,Ive always wanted to tear one down.wish me luck!

splittin' those suckers is cake if you have the tool. A nice guy at the local shop will prob'ly let you use one if you bring the motor in your truck (just the bottom) and literally split and hand it back to him. If you have the right connections, you can take it home and borrow it for the day.

I would try to avoid buying the tool. A flywheel puller is a must if you don't have one/borrow one. that is a good tool to have kickin' around.

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