SOHC.co.uk Forums > CB350/400

Helicoil and crankcase thread repair... opinions..!!

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Oz350Four:
GDay forum folk,

Cracking on with rebuilding a CB400F engine and have managed to purchase the requisite tools (micrometer and appropriate torque wrench) so that I can obtain the measurements to determine the correct bearing shells needed.
As you may have seen on a previous thread one of the crankcase bolts was swapped out with a head stud and topped off with a domed nut.
The previous owner probably did this because they had stripped the thread and the head stud was able to reach the last remaining threads...

So, if I am correct in what Ive read on this and other small 4 forums I need to torque down the cases so I can get a close measurement of the bearing ID and cross reference that with the crankshaft journal measurements to work out which bearing shell is required, however that is hard to do when one of the bolts is not quite right.

The question I have, is one of technical expertise regarding the use of helicoils in this situation. Even double stacking helicoils if need be.
Is this considered an appropriate fix to take or is it not worth it because of the bolts location and operating stress..???

Once agian thank for the feedback.

Regards...

Trevor

kevski:
My own personal thoughts are go for a time sert or big sert system as these are a better fix and come in various lengths, they cost more, but my view is pay cheap pay twice, others may view it differently.

Bryanj:
Dont think there is enough metal for a timesert, helicoils will work and you can getdifferent lengths of those.
Dont want to e rude but if you have just bought a micrometer you wont be accurate enough to work out shell sizes

Moorey:

 Nothing wrong with heli coils if done right.they are stronger than the original threads.

philward:
You mention double helicoils - I assume you mean one inserted on top of the other? (to cover full length of damaged thread?) If so, DON'T. if the 2 the helecoil threads end/start parts of the thread don't line up, you will lock the bolt/helicoil - you will struggle to remove the bolt and certainly the helicoils if they jam

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