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

[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

[Bryanj]

You may have to order them but helicol lengths are measured in multiples of diameter so an 8mm2d is 16mm long. Most firms only keep 1d coils but the longer ones are definately available

[Oz350Four]

Thanks folks... Will look at getting longer Helicoils...
Bryanj I'm not sure what you meant about the micrometer bit, happy to be informed...!!!??
Dont I need the two measurements (case ID and crankshaft journal OD)..??

Trevor

[Bryanj]

People who have been using mics for years may not be accurate enough for Honda tolerances, they used way more accurate stuff to get down to 3 decimal places properly

[Oz350Four]

Bryanj thanks for the info...  so I can get the crankshaft journals mic'd to the level required in the workshop manual.
Unfortunately I'm not in a position to spring for an uber accurate tool that I might only use once (maybe twice) short of taking the buttoned up cases to a machine shop I'm kinda stymied.
I have the letters on the end of the case (BBABB) and the numbers / letters from the crank along with the journal measurements that I have taken.
Is there any way of determining the shells required..

[Bryanj]

In the genuine Honda manual there is a table to cross refer crank codes to casing and rod codes giving you shell colours needed, its also in the parts book.
In the same table should be the pin sizes that Honda say fit the code given so you can check your measured size against that as well.
It takes a lot of practice to use a micrometer accurately, Honda used air gauges to get sizes.
Never seen casings wear or rods unless a siezure has caused a shell to spin and in that scenarion the case or rod is scrap

[Oz350Four]

Bryanj,

Thanks for the insight... It is a pleasure learning from those that have gone through the struggle before us...
Each step I take to completing this project has a huge learning curve to it and I'm appreciative of that...

[McCabe-Thiele (Ted)]

Bryanj,

Thanks for the insight... It is a pleasure learning from those that have gone through the struggle before us...
Each step I take to completing this project has a huge learning curve to it and I'm appreciative of that...

Screenshot 2021-04-10 132841 by Macabe Thiele, on Flickr