SOHC.co.uk Forums > CB750

Over torqued?

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Johnny4428:
Hi guys, after fitting of new pistons and rebore cylinders thanks to Julie and Trigger, I fitted and torqued down the cylinder head, backed off and torqued again, no problems all looking good. When I fitted the cam towers and tried to torque to the specified torque the threads seemed to strip without much torque at all. Well two, I tightened the rest by hand but wasn’t satisfied after fitting helicoils to two that was stripped. I am now convinced that there is some debris has found it’s way down the cam chain tunnel. So firstly I had to question how much torque I was actually putting on these bolts so ordered a smaller torque wrench that was hopefully more sensitive to lower settings. 4 to 18lb foot compared to 5 to 150lb foot. But having checked (very unscientifically) against the other the longer wrench 8lb setting wasn’t far off maybe just liable to slightly over torque. I don’t believe I had reached the specific torque before these delicate threads gave way. I must say there is something that is resonating in my head about helicoiling all these threads before fitting. (Trigger?) So onward and upward I will now dismantle again downed to cases and helicoil remaining threads clean thoroughly and assemble. I would probably be wise to get another head gasket?

philward:
You are probably over thinking the debri ending up in the bottom end BUT, I would probably do the same.
I personally wouldn't have any issues with helicoils (had to fit them to the cam tower retaining threads on one of the 750's I've rebuilt - bolts were just pushed into fully stripped holes!) and for piece of mind, I would put a new head gasket on.
Hope everything goes ok.

Spitfire:
Back in the olden days I had to get quite a few of those helicoiled, they seemed pretty prone to stripping.

Cheers

Dennis

Nurse Julie:
You can use the existing head gasket Johnny as the engine hasn't been run.

Johnny4428:
Thanks guys and Julie. I’m quite sure I hadn’t quite got the leverage applied before stripping difficult to gauge with that long lever, get a better idea with the shorter new wrench. The other thing is was the damage done before? Wouldn’t surprise me having witnessed some of the work done previously.

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