Topic: Stripped Sync/Plug Screw

[DennyK]

Folks,
My son and I are bringing a 1974 CB750 back to life.  This past summer we got the bike running; that entailed rebuilding the carbs and front brake along with a lot of other basic maintenance items plus buying plates and insurance.  The engine is strong but we need to do a lot to the bike to get it really roadworthy and we have started on our list of improvements. 

One of the things I noticed in cleaning the carbs was that one of the sync screws was slightly stripped.  We attempted to balance the carbs and I don't think we did a real great job, but we learned.  Going forward I want to be sure we can balance the carbs correctly and I think this sync port needs to be fixed.  A good friend who has done a lot of motorcycle repair work recommends using a Helicoil to make the repair.  The set screw is a 5m and you can get a Helicoil for that size.  My question is has anyone out there used a Helicoil in a carb body or are there other ideas?

Cheers

DennyK

[Vinhead1957]

How bad is it stripped ? Does the screw tighten? If so I would chase the threads with the proper size tap and use some Teflon tap on the screw for a short term solution. Long term, yes a helicoil

[dlhoulton]

Might consider after repairing using something like the Motion Pro permanent brass adapters so that you wont have to be worried about something like that happening again in the future. They come in different lengths so access wont be a problem. Here is one source to consider.
http://www.amazon.com/Motion-Pro-Permanent-Brass-Adapters/dp/B0012TTA5E

[DennyK]

Thanks for the quick replies guys.  Since I am going to have the carbs off the bike for the winter; I am going to go with the Helicoil fix and then get a set of those Motion Pro adapters to avoid any further issues with the other three carbs.  Thanks for the link, that makes it easy.

[ekpent]

Maybe if your lucky it will just be the threads on the screw/plug that are bad as I believe they are made of a softer brass alloy.

[DennyK]

Thanks for that comment. I will confirm that before taking next steps

[chewbacca5000]

I would go with a solid threaded insert like these http://www.ezlok.com/Home/index.html

All you do is tap and screw in.  I do not like using springs as fasteners at all.

[evanphi]

My #2 carb has this same problem. Whenever I go to sync my carbs I have to be VERY careful putting in the brass sync tube because it hits the choke linkage and makes it go into the hole sideways. I think I just need to chase the threads.

Slight hijack, but does anyone have a tip for getting those long brass inserts to NOT hit the choke linkage?

[70CB750]

I recently Helicoiled my #4 carburetor - after using silicon tape for two years.    It works.