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3 light cracks in crankcase

Submitted by christian_wyss on Sun, 25/06/2023
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Commando

Have a look at the pictures, should this be a cause for concern? What will be a good practice to take care of that?

Looks like it has been helicoiled.

Submitted by david_cooper on Sun, 25/06/2023

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It looks as if someone bashed the original stud sideways and damaged the inside edge.  Can you make out if how deep they are and if they change direction?  If they are short and vertical it doesn't look as if bits are going to break off.

Over to other views on what best to do.  I'd probably consider Lumiweld but I've zero experience of it.

Submitted by david_cooper on Sun, 25/06/2023

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I would do something.  That looks like it could escape.  I might be accused of being a botcher ...but I'd snap the bits off with pointed nose pliers to make sure they don't end up inside the crankcase.  And clean up the surface with a Dremel. There looks to be plenty of surface outside the stud to take the base gasket.  That bit isn't doing any good.

Nobody else has poked their head over the parapet yet!

You could put a copper stud in and weld it up.  The copper should unscrew.  But I would experiment elsewhere first...

Submitted by richard_payne on Mon, 26/06/2023

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An 850 presumably, with the Helicoil there ? It looks to me as if someone has wound the through bolt in, with old gasket cement and debris...enough for the hydraulic pressure to crack a casting as the Helicoil expands.

It's probably unlikely to fail catastrophically in the short term, but if you're building an engine for long-term ownership or hard use, then in my opinion the only proper way to do things for peace of mind is to remove the insert, Vee-out the cracks, weld and re-tap the thread.

You're right it's an 850. With Helicoils all around the crankcase mouth. You're right about the process, it should be the only way to go. But I'm not sure it's the best thing for me at this time.
I was mainly wondering about the strength of the remaining thread. What is the recommended torque here? It's rear LH side of the barrel.

Submitted by christian_wyss on Mon, 26/06/2023

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Good work ain't cheap.

The surprises continue. The problem actually arose because the threads in the crankcase were only half helicoiled. So the screws had to be cut, one is a bit longer, and the thread doesn't go high enough, so the unthreaded part crushed the material.

Crankcases' splitting is mandatory. Thanks to the previous mechanic. 

So what is the thread size for those studs. 

Attachments
Bolt cut.jpg

Submitted by steven_gould on Tue, 27/06/2023

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Those bolts look as if they went thread bound, there is a thick washer on those to allow them to seat in the recesses on the barrels and prevent the bolts from progressing too far down and possibly becoming thread bound on the shank of the bolts. Were the washers in place?

I can't see why the bolts were ever shortened.

Steve

Yes some washers are there, not the 06.4147, some grovers' ones squeezed in the recesses.

I can't see why the bolts were ever shortened.

We need to ask Motopow's, Fernsdale, MI. But they can't be reached...

 



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