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750 F2 chain damage to gearbox

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johnm37:
Hi to everyone. I'm a new member having only just dicovered this forum. I don't like starting by asking for help but I've a problem.
I got my bike out for it's first ride of the year. It rode for a few yards and stopped. A piece of rag had tangled between the chain and front sproket. Then I made my big mistake. I slackened off the chain and tried to force the rag round the sprocket. I now have a big hole in my gearbox. The damage only seems to be to the bottom part of the casing.
It looks like it's engine out to repair this.
Can I split the gearbox bottom without a complete engine strip?
My repair options seem to be: rebuild the area with epoxy putty. Stick the broken bits back in with epoxy or get the casing welded. That is my favourite. I could get the casing built up with weld or weld the broken bits back in.
What do you guys think?
I'm a capable mechanic type but with little experience on bikes.
The rest of the bike is ok. I don't want to sell it and like the idea of keeping as many original parts as possible.
Thanks in advance
John

Skoti:
Welcome to the forum John,
 
Yes you can split the motor without stripping the top end.
You could try a botch up with JB weld or something, nothing to loose.
The proper way is a weld repair which has already been documented some where on this forum.

Good luck

Skoti

Bryanj:
What you could do ismeticulously clen and epoxy the bits in so you can use then have it welded when the engine needs work.
Depending on mileage it could be due exhaust valve guides anyway, they only lasted 15 to 30,000 anyway

Martin6:
Feel your pain. Are you certain nothing has gone inside the case?

johnm37:
I'm fairly sure I've got all the bits out. I've looked at an epoxy repair. It's a possibilty but supporting the broken parts while the epoxy sets isn't easy and there's not much clearance between the case and gears.
I'm thinking it's engine out and weld the bits back together. That way I can check the internals at the same time.
I might also look at other things while it's out. I wasn't aware of the valve guide issue. I may check those at the same time.
How do I split the crankcase without removing pistons etc? Getting at the main bearing bolts seems an issue. It sounds like I can check the crank bearings too.
The bike has only done 15,000 fairly careful miles so I'm hoping it won't need much work.

John

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