Carby thread stripped

[Andrew Henshall]

A Bradford owner has just rung me to ask if anyone has successfully repaired a stripped thread in the carburettor housing where the fuel supply banjo bolt fits on a CC Bradford?

Any idea what thread form the banjo bolt is, and if there is a helicoil insert to suit? Is there even enough "meat" around the thread to insert a helicoil?

Cheers,

Andrew

[Keith Clements]

Spoke on this very subject with Neil More in NZ recently. The threads are metric so a helicoil should be available. The issue usually is enough meat in the casting to hold the insert. One might try Lumiweld or some other low temperature braze to build it up. I will have a go with my TIG on a scrap one with some high silicone filler rod and see if that is possible.

See this topic

[Tony Fearn]

Hello Andrew.
I used Araldite on my petrol pump when a bit of the casting broke away where the brass elbow joins it from the petrol input pipe, and it's lasted 8 years, but I don't think I could dismantle it again.
If the high tech helicoil route isn't feasible, then a coating of the banjo bolt thread with Araldite, when the female thread In the carb is cleaned up of oxidation, and everything is ready to assemble, could possibly save the day.
The bolt would only have to be finger tight, and perhaps fibre washers might be of use, with the Araldite on both sides so that it oozes when the bolt is tightened.
Make sure the Araldite doesn't block off the petrol flow.
Of course it's a one off fix - if it works.
Tony.

[Andrew Henshall]

Thanks for the suggestions; I look forward to your update Keith following your trial.

My only thought was to use Devcon, which is a very useful product used by auto manufacturer's prototyping areas to modify & repair castings. It can be drilled, tapped, machined or painted.

Cheers,

Andrew

[Keith Clements]

I have tried similar, but not successfully. That may have been because the surface was not clean or some other reason. My method was not to rethread but to stick the banjo in with it. I put some wax on the thread in the hope I could extract the banjo.

[Andrew Henshall]

I've learnt that stripping the thread in the carby housing where the banjo bolt fits is fairly common: several Morris models use the same 30VM carby. A mate with a Morris said that it is possible to replace the original M12 x 1.25 thread with 1/2" UNF (20 tpi), which is very nearly the same pitch (1.27mm i.l.o. 1.25mm), but 0.7mm bigger in OD. They then machine a special 1/2" UNF banjo bolt out of a regular 1/2" UNF bolt.

They are going to try to tap the inlet of the carby out to 1/2" UNF and see how it goes, then send me feedback.

Regards, Andrew

[Andrew Henshall]

Success! Tapping out the inlet to 1/2" UNF and a new banjo bolt to suit has solved the problem.

Andrew

[AlanBartlett]

This has just happened to me on the fuel pump of the Bradford, will see how I get on with the above suggestions.