Best "fix" for stripped carb float bowl threads?

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MexicoMike

MexicoMike

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I have one stripped thread on one of the (Amal MK1) carbs float bowl. It has been that way since I bought the bike and the PO solved the problem with an oversize screw. It works fine but it offends my sense of how things should be. So what's a good fix for this to allow the correct screws? There is very little surrounding metal so I don't believe a helicoil would be able to be inserted without the hole actually breaking out of the side of the metal. Currently, I have the proper screw in there by placing a couple strands of copper wire in the hole which works fine but that offends me as well. I CANNOT deal with having one different size screw. Help me! ;)
 
Loktite makes a product called (I think) Form a Thread
It's a kind of epoxy that you put in the threaded hole and insert the screw. Makes fair threads...
 
I think those screws are some Brit size, but close to a 10-32. You could try tapping the buggered hole with a 10-24 or a metric size slightly bigger than what's there. If it holds OK, do the same on the other 3 so they're all the same.

You sure there's not enough meat for a helicoil?
 
"You sure there's not enough meat for a helicoil?"

No, I'm not sure but it looks mighty thin at the outside wall...
 
There is a thread repair called a Time-Sert which is much more substantial than a helicoil, but I couldn't say if it comes in the proper size for an Amal float bowl. I'm sure you're refering to the threaded hole in the bottom of the carb body and it's true there's not much meat there. Before I went with an epoxy, I'd leave the oversized screw in there. If it ain't broke, don't fix it.
 
maylar said:
I think those screws are some Brit size, but close to a 10-32.
Click to expand...
I have a nearby hardware store that sells stainless nuts, bolts etc and there was no SAE or metric match for the Amal bowl and top screws. I ordered a kit which presumably came from the UK. Most likely a British Standard or Whitworth thread.
 
Being a purist is one thing, Mike. Being anal over a screw hole is something else. That being said, we all have our demons. Unless you get another carn body, you will never be right with who you are as a Norton owner.

The Zen of Norton says "to get things right is a straight forward process with the Norton and for a blissful ride, all things must be right."

Your petance, grasshopper, is to run this carb on a beautiful day for nice long ride with a zip strap holding the float bowl in place on that side while repeating to your self "I will make it home! I will make it home" throughout the ride.

Just kidding,Mike............not about the Zen thing, though.
 
FYI
There is enough room for a heli coil. I have repaired one of my 932's to correct a stripped bolt.
Regards,
CNN :mrgreen:
 
Mike, hopefully you can helicoil, but if not, could you fill the existing hole with JB Weld and retap for a new proper sized screw?
 
They are 2 BA witch have 31 1/2 threads per inch Also used on levers tail lights, badge screws. And were ever else the electricians could get their 2 pence in. In American a # 10 screw is 3/16 in diameter 32 threads per inch.(24 as well) It is close but not quite right if you run a tap that size through first one can convert the whole lot than use S.S. socket head cap screws, this is done often making road side repairs easier. In the past some guys have had some batches of 2 BA socket head cap screws made up.(check with British fasteners in New York)
A 5MM screw is about .010 bigger and might be a nice way to get them all the same and in good order. But finding a 5mm screw with the American Posi drive heads might be a trick. Back to doing S.S. socket heads or a Pilaster head with Phillips head.
 
"Mike, hopefully you can helicoil, but if not, could you fill the existing hole with JB Weld and retap for a new proper sized screw?"

Well, I'd prefer the helicoil, having used them extensively. OTOH, I happen to have some JB weld. I've used it for a lot of things though I never tried thread repair but It wouldn't cost a dime to try it and if it doesn't work, I'm no worse off than before. Nobody seems to have heard of helicoils here anyway... ;)
 
Will a 10-32 tap not damage the 2BA thread in the Amal carb float and top covers so as not to be usable? I would love to put 10-32 Allen head SS machine screws in them instead of the pricey 2BA Allen heads, being a cheapskate? Maybe we could call it an improvement, not Zen.

I have replaced the 2BA hex heads in the fender/stays with hex 10/32 and the rear license plate screws (the long ones) with the 10-32 philister head with no adverse affects.

Dave
69S
 
Had a friend use JB Weld over a helicoil that pulled out and he seemed to think it worked good. I dont know if it would be good for a carb though, usually those aren't exatly maintenance free, not sure if it would work if you keep putting the screw in and out.


-My 2 cents
 
I have one stripped thread on one of the (Amal MK1) carbs float bowl.
Click to expand...

First I believe you mean you stripped the thread in the carb body. It would be a lot easier if all you needed to do was find a new float bowl. British Fasteners sell 2 BA helicoil kits. I stripped one of those myself, and I blame the stainless socket head screws I was using. I suspect they were not 2 BA but maybe 5mm metric. In any event it took very little torque to strip the threads.
I replaced the body on mine intending to try the helicoil at a later date. The points plate screws are also 2 BA and I stripped one of those when I crashed my Interstate, so I have a set of proper helicoils in the toolbox.

As a get home fix, a small 6-32 machine screw with a nut will fit and seal the bowl to the body. I now carry one in my toolkit.
 
I had a bowl screw fall out on me. I felt wet on my leg and then smelled gas. I drove home easily as one just throttles the fuel tap when needed. Not having the correct screws, I found Rochester two barrel air horn top screws worked perfectly. They are 10-32 I believe and I ended up replacing all the bowl screws with these. They go in nice and firmly like a locking screw. Never had any problems since then. I know this may not be for you, as your bike is so perfect.
 
I have repaired a float bowl thread using M5 metric (coarse).

As M5 is only slightly larger diameter than 2BA (4.7mm) and M5 coarse pitch (0.8 mm) is almost identical to 2BA (0.81 mm).
 
As far as I've seen the only difference in 10-32 Whitworth and Americn is the 55 degree angle on the threads. British screw fits in American thread, but not vica versa.
 
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