Cylinder head helicoil thread

Status
Not open for further replies.
rvich said:
Or you take old head bolts with 26 CEI and cut off the head, then thread the end with 3/8-16 and you are ready to go. Oh - and make them a little longer too! OK, flame suit on!
Click to expand...

That is another method that works very well. The headbolts are made of pretty good stuff though and require a good die to cut them.
 
Last edited:
Once you start making studs, regardless of the threads on either end, the price is, roughly, the same. The UNF and UNC taps/dies are readily available and the available quality is much broader than the same tools in BSW or BSC.

When I was having sleeve nuts made the shop doing the work would have to purchased almost twice as many taps for the the 3/8-26 work saying that they (me too) couldn't find "production quality" BSC taps.

Again, if you are looking for a "Comnoz" grade solution to head fastening you won't go wrong with adopting his implementation details/protocols; if you are trying to cheap-out, it will, at some point, came back and bite you where it is least expected and most painful...

Best
 
I had Comnoz perform this same mod for me when he repaired my failing exhaust threads. Close to ten thousand miles later, and not one sign of seepage (composite/flame ring gasket, Yamabond #4 sealer).
 
Nater_Potater said:
I had Comnoz perform this same mod for me when he repaired my failing exhaust threads. Close to ten thousand miles later, and not one sign of seepage (composite/flame ring gasket, Yamabond #4 sealer).
Click to expand...

it seems to me that once you get past the new status and the bike has a number of miles, there are a number of well documented "fixes" which are desireable from a long life perspective, updating the 3 studs is #1, the exhaust thread repair by Jim Comstock is #2. once the head is off, do them both, but then you should also consider, valve guides (bronze) and kibblewhite valves #3... buy the CNW head kit which addresses # 1&2

next step is a cam... and now we are off topic...
 
Treat the symptom or the cause....... or

Cylinder head helicoil thread


:D
 
comnoz said:
You look younger in this picture than I figured you were.;)
Click to expand...

I tried to find a google pic with some resemblance but thanks for reminding me, 60 in Oct. :D

Cylinder head helicoil thread


No studs today.
180 grams of Mallory (309L on pulse) metal and back to Norton's tomorrow.

Cylinder head helicoil thread


Cylinder head helicoil thread
 
Hello Laurent,

Contact Jean-Paul M.il did it on mine 2 years ago, since 4500 miles and no more worries.
Francis.
 
Last edited:
Coming back to an earlier comment, the cNw head kit contains new proper studs and the waisted stretch bolts developed by Jim (comnoz) which seem to be the ultimate solution to the problem of the fasteners loosing their torque and causing the head to leak oil and /or blow the head gasket.
Generally, I stick to normal fasteners instead of going the stainless route, but this kit is well worth the extra money in my view.
 
Thanks to you all guys for your recommendations.

Francis, I was at Jean-Paul's on Monday. He did a very good job as usual. I put the cylinder head back on the engine yesterday, had a 100 km test ride this morning in the Vercors and re-torqued the head this afternoon. Everything is OK.
A bientôt.

L.
 
I contacted AN and got a prompt reply so maybe the correct stud for a cock up half a century ago might be rectified.

I bought some high quality 20 TPI bolts to make into studs to suit the FA cylinder head.
Screwed one into it, wobbly, screwed it into the JC inserted RH1, perfect.

To change the FA head to 16 TPI JS Motorsport studs ($164 + International post) plus a Time Sert kit ($256 + post) will be a fairly spendy operation even doing the installation myself.

My hope is and for all the other 30000+ Commando owners with stock 20 TPI heads is AN will produce a revised stud that uses all the thread in the cylinder head.

Good to see the OP got it sorted.
 
Be sure you order the correct length Timesert and the special bottoming tap to install it as in the vid below:
 
Thanks for the reply Jim.
Plus a bottoming tap so it looks like it will be close to a AU$500 repair on a already $4000 cylinder head, not to mention the dodgy valve seat which some idiot hit with a grinding burr and said whoops, stick it in the box.
I will cut back on food to raise the funds.:D

Cylinder head helicoil thread Cylinder head helicoil thread
 
For options - there is also an oversized Timesert with a larger outside diameter for those who are repairing threads that have already been helicoiled.
 
Status
Not open for further replies.
Back
Top