I need replace my engine bottom crank case

Hi all.

I have an 1980 XJ650 4KO and I need to replace my engines bottom crankcase.
Currently I can find a reasonable clean looking crankcase for a 1981 4H7. Does anyone know if the 2 cases are compatible?
Thanks

 

I don't think you can replace half the case as the crank main bearing areas we're line bored at the factory. We'll that's what l read on this forum.

 

Shouldn't it be possible to replace the bearings too though?

 

No, you have to keep top and bottom crankase halves together, as @Franz said, they are machined together.
If you were to replace both, you will still need to check main bearing fitment.
Is your lower case not repairable?

 

What is the condition of the crankshaft??

I think we need more details and perhaps some photos

 

Ok. So it's either repair or replace entire bottom end then. The crankcase engine mount has broken off (see photo).
The engine was not run with the gaping hole there, so I'm relatively certain that no other damage was caused.
I'm doubtful that the case can be repaired given that it a stress point?
Thanks
Steve

 

I read aluminium can be welded at high stress points but it would need to be Tig welded by someone with the expertise to do it properly.

 

There's a couple of places nearby that offer aluminium TIG welding services for engines. I'll call them.
Ultimately, I'd really prefer not having to change the original engine number on this machine, so all this helps.
Thanks for the advice all.

 

@Minimutly knows about welding aluminium he might be able to offer you more advice.

 

Wow. That's some damage you don't see every day!

 

i had exactly the same damage on my xj600 , it was atempted to repair by PO. with a 2 pack resin, obviously it leaked, so i split the bottom half case off and took it to a scooter repairers, who do this type of repair on Lambreter and Vespa scooter engine/shock mounts, the guy repaired it without any problems, he did say he would have to heat the whole half case up to enable the ally weld to take. good job done ,but it did cost me £130 GBP, but ive retained the original engine number

 

The welder will want just the bottom casing and the mount, I would recommend you get a propane torch and wire brush on both to remove the paint near the area to be welded, then clean everything scrupulously before presenting it to him. The weld repair is a 10 minute job, cleaning and prep potentially 2 hours... This is your best course of action.
If you were desperate it could be tipped upside down, cleaned and welded in place, but I would not be recommending this unless you were stuck in the desert!