VM20 carb rescues.
Posted: Thu Aug 06, 2020 10:19 am
I just managed to rescue an otherwise doomed VM20 that had two situations. The first was a main jet that wouldn't unscrew because the pin that locates the needle jet had been broken off and there is no way of otherwise holding the needle jet.
I hammered a flat on the end of the little brass pin and used a 1/16" drill to drill it out. Yes, you have to be careful to drill on center and go slow as it will probably just spin with the bit and come out before you've gone much past the head. I then used a 14 gauge bicycle spoke - the most common 2mm size - and screwed it in until it just bottomed on the jet slot and then backed off a quarter turn. A Dremel cut off the spoke and I left about two threads to grab if ever it needed to be removed.
The great mystery of why some carb tops are loose on some carb bodies and not others is just a feature of these carbs. This carb was so bad that the cap just didn't grab at all despite the threads looking fine. Another cap was marginally better but it was as if the carb had shrunk. So I put the cap in the vise and cut through it with a hacksaw. Some stainless lock wire twisted tight around the boot groove closed up the gap and it went on like it is supposed to. I then put a hose clamp on it and locked it in place. I know, it's a bit ugly, but you can use the narrower style clamps that don't shout hose clamp quite so much. I guess you could also cut a groove through the nubs and put some serious wire around it, but the clamp seems like a more secure way to keep it from loosening, which has been a feature of this carb since the beginning.
I hammered a flat on the end of the little brass pin and used a 1/16" drill to drill it out. Yes, you have to be careful to drill on center and go slow as it will probably just spin with the bit and come out before you've gone much past the head. I then used a 14 gauge bicycle spoke - the most common 2mm size - and screwed it in until it just bottomed on the jet slot and then backed off a quarter turn. A Dremel cut off the spoke and I left about two threads to grab if ever it needed to be removed.
The great mystery of why some carb tops are loose on some carb bodies and not others is just a feature of these carbs. This carb was so bad that the cap just didn't grab at all despite the threads looking fine. Another cap was marginally better but it was as if the carb had shrunk. So I put the cap in the vise and cut through it with a hacksaw. Some stainless lock wire twisted tight around the boot groove closed up the gap and it went on like it is supposed to. I then put a hose clamp on it and locked it in place. I know, it's a bit ugly, but you can use the narrower style clamps that don't shout hose clamp quite so much. I guess you could also cut a groove through the nubs and put some serious wire around it, but the clamp seems like a more secure way to keep it from loosening, which has been a feature of this carb since the beginning.