Popping on Overrun
- Thread starter bmetcalf
- Start date
One hand on each bellmouth - work the twistgrip with your teeth!
Until last week my Comet wore a rather knackered Monobloc on it and I could wiggle the slide in the chamber bore with my finger. The popping and banging was getting embarrassing . A pal has loaned me the correct 229 carb, recently refurbed and it is running now as sweet as the proverbial nut.
BTW the exhaust nut was a non standard o/size .A new o/size bronze nut was made by a very nice man I know in Cornwall, but I dare not insert the gasket which butts up against the flange in the port. (I found it very difficult to swage the flange on the ss pipe so too much radius) and not wanting to put the otherwise good thread at risk simply assembled with copious quantities of silicon gasket. If ever this was prone to leaking it would be now but seems good. I have placed an ad for someones unwanted 229 carb body in for MPH wanted ads (I have a float chamber) The new ones are simply too expensive for me. Happy to swap for anything useful also. Hope you sort it soon
BTW the exhaust nut was a non standard o/size .A new o/size bronze nut was made by a very nice man I know in Cornwall, but I dare not insert the gasket which butts up against the flange in the port. (I found it very difficult to swage the flange on the ss pipe so too much radius) and not wanting to put the otherwise good thread at risk simply assembled with copious quantities of silicon gasket. If ever this was prone to leaking it would be now but seems good. I have placed an ad for someones unwanted 229 carb body in for MPH wanted ads (I have a float chamber) The new ones are simply too expensive for me. Happy to swap for anything useful also. Hope you sort it soon
John,
I have flanged the steel pipes easily, but on the stainless pipes I have welded on the flange. It was for another owner, but the piece I welded on came from a used Vincent bearing as I remember.
I do not know the prices, but I think it is worth quite a bit to have a new tight carb, even if it is not original. I have run the new monobloc as well as the Amal MK 2, which I prefer to the Mikuni.
If the nut is a little loose in the threads, Maughan Ex nuts are slightly oversize (at least the one I fitted was) and it will restore the fit of the nut quite nicely.
Good Luck!
David
I have flanged the steel pipes easily, but on the stainless pipes I have welded on the flange. It was for another owner, but the piece I welded on came from a used Vincent bearing as I remember.
I do not know the prices, but I think it is worth quite a bit to have a new tight carb, even if it is not original. I have run the new monobloc as well as the Amal MK 2, which I prefer to the Mikuni.
If the nut is a little loose in the threads, Maughan Ex nuts are slightly oversize (at least the one I fitted was) and it will restore the fit of the nut quite nicely.
Good Luck!
David
David,
Thanks. In hindsight welding the flange on ss sounds like a good solution. The head was bought from a pal and was in lovely condition the ex port thread looked like new, that is because it was more or less. A knowledgeable local member said he recalled a chap in our area that made up a set of o'size taps and used them to restore threads and made nuts to suit. All long in the past now. The thread itself was 1.895" ID and I had a new nut made this size and it is spot on. Interestingly of the three oe bronze nuts I had, one was very tapered from 1.855'' at the end and 1.875 " ( the correct size ) at the fins end, but all were tapered to some extent. Even with this o/size cut in the port I still managed to turn a little off the end of an oe nut and then get it to hold by the skin of its teeth on about three threads using the old steel ex pipe, again without a gasket so I could get the threads as far in as possible to bite. I got going with this but the risk of serious damage to the head with more expensive remedial work was not worth it so I asked for help and the results are excellent, our club is still one of the best in that respect.
I agree about the 229carbs. But they really are stupid money now. They weren't cheap to start with when they first appeared a couple of years ago but are now £310 before VAT without a float chamber ! I am trying to get my Comet a little more original but it is a very modified bike anyway so I am redressing the balance as it were, and it goes so well with the oe carb oddly enough !
I get the feeling (call it paranoic if you like) they are trading on the name and have the perception that all Vin owners are millionaires. Materials don't come into it because they charge the same for the rhs alu carb as the l/hand bronze job.hey ho atb J
Thanks. In hindsight welding the flange on ss sounds like a good solution. The head was bought from a pal and was in lovely condition the ex port thread looked like new, that is because it was more or less. A knowledgeable local member said he recalled a chap in our area that made up a set of o'size taps and used them to restore threads and made nuts to suit. All long in the past now. The thread itself was 1.895" ID and I had a new nut made this size and it is spot on. Interestingly of the three oe bronze nuts I had, one was very tapered from 1.855'' at the end and 1.875 " ( the correct size ) at the fins end, but all were tapered to some extent. Even with this o/size cut in the port I still managed to turn a little off the end of an oe nut and then get it to hold by the skin of its teeth on about three threads using the old steel ex pipe, again without a gasket so I could get the threads as far in as possible to bite. I got going with this but the risk of serious damage to the head with more expensive remedial work was not worth it so I asked for help and the results are excellent, our club is still one of the best in that respect.
I agree about the 229carbs. But they really are stupid money now. They weren't cheap to start with when they first appeared a couple of years ago but are now £310 before VAT without a float chamber ! I am trying to get my Comet a little more original but it is a very modified bike anyway so I am redressing the balance as it were, and it goes so well with the oe carb oddly enough !
I get the feeling (call it paranoic if you like) they are trading on the name and have the perception that all Vin owners are millionaires. Materials don't come into it because they charge the same for the rhs alu carb as the l/hand bronze job.hey ho atb J
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What you do with your tapered threads, is to have a tapered steel drift, and heat the nut a little, and tap the drift in, until you have restored the thread back to parallel. The taper has been induced by heavy handed tightening, over the years.