Splitting the crankcase


XS650 Enthusiast
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Paris, Ontario
Since i bought my bike, First gear sounds like it's missing a tooth. (It reminds me of a clangy bell they put on a fork lift wheel at a summer job in high school).

So I've been attempting at splitting the crank cases, so i could investigate the gear issue, both the Haynes, Clymer, and Yamaha Manuals all state "Remove bolts in order from 18 to 1. the number is stamped next to each bolt/nut."

I don't know about you guys, but my bike is from 1978 and has had it's fair share of greasy junk on mostly the bottom of the engine. The previous owner didn't take the best care of it.

That being said, it's like finding a needle in a haystack to find these little numbers. (is it a 6 or a 9?)

Does anyone know what number the bolts/nuts are, and their locations?

Can I leave the alternator and clutch assembly on?

Any information would be extremely useful!
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- need to remove the clutch to get the bolt hidden behind it
- may as well replace the seals while youre at it too - means removing the alternator

- top box reads...removing-begin at #18, loosen half a turn each, repeat from #18
- bottom box reads...installing-start at #1, tighten half a turn each, repeat from #1

- 1st photo is the front sprocket shaft
- 14,15,17,18 are at the rear of the motor
- 9 is behind the clutch
Not to sound stupid, but i have this manual on my desktop, i forgot about it. Plus, I don't read German. :)

I have a full gasket and seal set that i was going to use.

Thank you so much!
How hard is it usually to get the case to split once all of the nuts and bolts are loose. I just double checked I went through all 18 and the case doesn't seem to want to split even with some persuasion from the rubber mallet.
From what I hear you need a 20 ton press to pull them apart. Somewhere on pirate4x4.com there is an awsome motorcycle build thread. The kid is super smart. He splits the crank with two nuts and bolts. Just opens the nut and bolt til the crank splits apart.
Yeah, they can be a bitch to split (breahn, he's splitting the cases, not the crankshaft).

Sit the motor in the sun (if your getting any) for a couple of hours can help. Be careful if you have to start prying it, can break bits easy!
Its on that pirate web page. I stumbled on it through chop cult and his bike is on 650chopper.com. He rephased it, that's why he split the crank. I'm on my phone so its hard to find the link but look around, you'll find it on pirate.
NoValidTitle, I know what you mean how hard it is to split, once you get the bolts & nuts out.

I have mine completely upside down, and i whacked all around on it with a black rubber dead blow mallet. eventually it started to move one mm at a time. The back bottom right of the engine came loose first, i carefully slipped a pry bar in between to open it up more. and i did the same at the front bottom left. Be extremely careful, i left no scratches, and i put something soft in between the pry bar and the mating surfaces.

It's a huge feeling success when you get it.
Well I got it split today! I made a makeshift oven with some scraps I had around. I got it up to about 200F and then gave it a few taps on the seems and she split right open.