SOHC.co.uk Forums > CB350/400

Helicoils pulled out, replace or go size up?

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billdn:
So cam shaft in, see earlier post. While torquing up the 4 bolts on cam cover, 3 wouldn't tighten. So undid them and out come 3 helicoils installed by previous owner I presume.  The 4 bolts  are 6mm x 60mm and are the ones that fit around the cam chain sprocket in the cam cover.
Just one thing after another! 😤
So question is , can they just be replaced by putting in same size or do I need to go up a size, although not a lot of room for that ?
Fear I know the answer 🙄

Nurse Julie:
It depends on what the threads are like Bill. I take it you have all the tappets backed off fully and the rocker arms held up out of the way with rubber bands and if possible, someone pushing the cover down flat when you're trying to do the bolts up to reduce the pressure?. It's very rare to pull helicoils out unless there is an awful lot of pressure being exerted on them. If the helicoils had have been loose, why didn't they come out when you stripped the top end down 🤔🤔🤔
It's very, very easy to bend valves and crack the valve guides without taking the pressure off by doing the above.

Bryanj:
If they have unscrewed you can replace them, if they have pulled out its a problem.
Are they short coils in deep holes? If so an answer is possible but complicated, i dont think there is metal for timeserts(they need a 10mm outer thread)

billdn:

--- Quote from: Nurse Julie on June 06, 2022, 11:09:02 PM ---It depends on what the threads are like Bill. I take it you have all the tappets backed off fully and the rocker arms held up out of the way with rubber bands and if possible, someone pushing the cover down flat when you're trying to do the bolts up to reduce the pressure?. It's very rare to pull helicoils out unless there is an awful lot of pressure being exerted on them. If the helicoils had have been loose, why didn't they come out when you stripped the top end down 🤔🤔🤔
It's very, very easy to bend valves and crack the valve guides without taking the pressure off by doing the above.

--- End quote ---

Thanks Julie, all tappets fully backed off before assembly.  To be honest hardly exerted any pressure because I'd noticed they looked like helicoils when stripping down. I took them back out because just didn't feel right, you know that feeling of dread !

billdn:

--- Quote from: Bryanj on June 06, 2022, 11:31:03 PM ---If they have unscrewed you can replace them, if they have pulled out its a problem.
Are they short coils in deep holes? If so an answer is possible but complicated, i dont think there is metal for timeserts(they need a 10mm outer thread)

--- End quote ---

Cheers Bryan,
I would have said they've unscrewed rather than pulled out as not at full tension imo.
Although bolt is 60mm the threaded part is 15-20mm  in 25-30mm hole. Estimated measurements. 
Best guess is try and reinstall and see what happens , if that won't go in original helicoil thread then obviously they pulled out rather than come undone.

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