oops, studs penetrated the case

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WallysmotordemonsWMD

New Member
Jun 2, 2014
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Springfield, IL
I was doing improvements to my little BGF ebay engine. Ordered some SBP Grade 8.8 cylinder studs. Torqued them down into the case then installed the jug and head and torqued the nuts down. Tried a ride, no start and a terrible squeal then the back tire locked up. It appeared that the crank seized.

Upon disassembly saw the pictured penetration into the crank case from one of the studs. Crank was contacting the metal in about 90 degrees of rotation and caused a small scratch on the very outer edge of the crank, not a big deal IMO.

Now, should I just replace the case, or can I Dremel the pooch of metal smooth and try again? Of course being very careful when re-installing the studs. Perhaps only torque them into the case at half spec, then full spec after the jug and head are put on. Maybe grind off a thread or two in the one stud that broke through the case?
And yes that is a less than a quarter inch hairline crack on the pooch of metal.

Also, the clutch shaft will not come out, don't want to beat on it too hard, am I missing something?

Thanks in advance for all your help!!
 

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fatdaddy

fatdaddy

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May 4, 2011
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I'd probably just use locktight on the stud, Screw it in to the proper depth, let it set. Then make sure the head nuts go on smooth so ya don't drive in the stud any further. It looks like a chunk of yer case might come loose and wind up in yer bottom end, NOT a good thing. I really don't know if you should try to remove it or not. BUT you are gonna have problems if it falls into the bottom end.
fatdaddy.usflg

IF yer gonna use that case don't worry about the clutch arm. If ya order a new case yer gonna probably screw up the bearing getting it out. You can save the clutch arm,But probably not the bearing.
 
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YesImLDS

YesImLDS

Member
Jun 29, 2013
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Might be safer just to get another case if you already got it torn apart? I would be if you were to take that chip off and seal it up you wouldn't have any other problems, but why do that when you can spend $15 and get a new case.
 
fatdaddy

fatdaddy

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YesImLDS said:
Also clutch I usually have to use a rubber mallet to get it out.
Click to expand...
I've never had problems with tight clutch arm bearings in the past, But the last year or so, I think they changed the assembly method, A heavy press or something. Last time I did one, Getting out that bearing was a challenge.
fatdaddy.usflg
 
Venice Motor Bikes

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I think the case is ok to re-use... Just break off the loose pieces of metal & use good sealer on the stud threads. (^)

Also... Heat the case with a heat gun & the clutch shaft bearing will easily fall out. ;)
 
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WallysmotordemonsWMD

New Member
Jun 2, 2014
19
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Springfield, IL
Thanks for your help!
Got a case for $22, think I'll go that route,
heat gun trick worked for the clutch shaft, but not the bearing, it's toast.
New set of bearings $15, will update how they fit in new case.
Lesson learned, don't torque studs into case! (at least don't overdo it!)
Thanks Again.
 
MEASURE TWICE

MEASURE TWICE

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Jul 13, 2010
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For the fact you got a replacement case, this is sort of mute point. I had tried to drill a steel rusted broken off bolt head remains from the outside wall of a crank case. This was for one of the engine flywheel cover fasteners. Not knowing that the threads were real close to the inside of the crankcase of the engine. When I ended up veering the drill it broached the wall of the crankcase.

I made do, keeping the old crankcase by plugging the hole with a Heli Coil for new threads and the 1/4 - 20 bolt I coated the threads with high temp RTV. No problem ever noticed 7 years running.

MT
 
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