weak/stripped threads on top of carb body

[kevhed]

My top cap threads are in good shape but the male threads on the top of the carb body are very weak. So much that the top cap can't be screwed tight and occasionally pops off. I am also getting some weak "return to idle" issues. Slow to come back down.

Has anyone had any luck building up the threads on the carb body or otherwise securing the top cap to the body?

Thanks
Kevin

[hornetgod]

The weak return spring and throttle friction are both very common in older Trail 70's Many have sticky throttles. The threads on the top of the carb being worn out is a first for me. You could try a new cap or some of that white thread tape. I bet the cap was over torqued at one time stripping/weakening the threads. That should only be hand tight.

[motodevo]

i had the same problem on a PE250 carby due to overtightening by PO. I just put some loctite(thread locker) on the threads, it holds it on well but you can still undo it when required and re-loctite it back on. Try lubing your throttle cable but if its the internal throttle type(earlier models) even if you lube all the parts they still tend to stick a little, infact they did from new, think of it as cruise control

[Carlyboy]

The loctite sounds like a good idea. I haven't had it happen to my K1 but can see how it can as there is not a lot of thread nor is it strong. All it would take is to be tightened crookedly .too tight or just from use over the years.. I'd be interested to see what other comments come up and if permanent fix can be done.

[zeriods]

Go to a local supply company that sell's tooling, and equipment for machine shops. Get a thread file, make sure you have the right thread pitch, and you should be able to fix the threads. I have used them in the past and they work fine. Just take your time.

[racerx]

There's also thread repair epoxy. It's a tad tricky to use but might be ideal for this application, since the threads are lightly loaded (normally) and you're a step away from replacing the carb body anyway. Loctite makes this material, or at least they did in recent years.

Otherwise, it might be possible to build up the threaded area with low-temp aluminum solder, then machine it back to the right diameter and recut new threads. Frankly, the process would be too involved & costly for a CT70 carb. It could be done but it'd make more sense to source another carb.