Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: billdn on June 06, 2022, 10:24:48 PM
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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 🙄
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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.
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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)
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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.
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 !
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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)
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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Maybe some new inserts with a little loctite 2620? It is certainly worth trying before anything more remedial.
Matt
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I wouls advise buying a helicoil kit and carefully retaping with the special tap then measuring carefully the depth of helicoil thread in the head and buying correct length coils, they come in 1d, 2d, 3d, etc where d is the diameter of the bolt. If necessary get a longer one than hole is deen and after fitting coil use a square or triangular needle file to cut the coil just below head surface
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Get yourself a V-coil kit and re-tap and put a new coil in >>> Link >> https://www.ebay.co.uk/itm/354074603431?hash=item52707dafa7:g:jqIAAOSw3qpimPFJ
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While torquing up the 4 bolts on cam cover, 3 wouldn't tighten.
That sounds ominously like the screw is slipping in the coil insert or the coil is slipping in the hole. So get the longest insert you can, they come in 1/2 d lengths as well. Difficult to judge as the insert comes tightly coiled (wind it on a screw, it should be the 6mm/9mm etc). Also see if a fractionally longer screw can be fitted, but be careful.
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Get yourself a V-coil kit and re-tap and put a new coil in >>> Link >> https://www.ebay.co.uk/itm/354074603431?hash=item52707dafa7:g:jqIAAOSw3qpimPFJ
Thanks Trigger!
I have a helicoil kit but not the one you mention. I'm guessing over the years experience has shown that this to be the better , more durable and precise tool ?