Mikuni carb repalcement

You can get the carb you want from Sudco. If they do not have the specs for the 78 390 you have, you can give them the jets and slide required. Make sure they are working with 78 specs , not 79 or later. On early tests the 79 390CR came with the 78 specs and on the test repeated seizures were experienced. It was found that the airbox flow was increased over the 78 airbox by 300%. That forced a main jet change from 340 to 370-390 to get the proper fuel air mixture.

I got a new Mikuni from Sudco. The fellow that helped me was great. He educated me telling me they don't have the original specs for the 38 Mikuni that Husky ordered for their 78 bike. So I sprung for a new 38, ordering it with with a slide and air jet size that came in the 78 carb originally. I jetted it to match my old carb. I used the same needle jet and needle size. It was darn close. I started out with the stock 45 idle, but went all the way down to a 30 to eliminate almost all of the blubbering when cracking the throttle. I ended up going was a size richer on the main, up to a 440, and one slot richer on the needle clip, now two slots up from the bottom. I didn't mention it in the original post, but my idle was hanging before. I double checked everything and there was NO air leak. My bike now idles like it should. Raced yesterday and the bike ran wonderfully. So.....there was something a miss in the original carb, I truly was chasing my tail, and I'm glad I dumped it for a new one. I've had issues with the original carb on my 250 Mag, so I'm going to shelve that old carb and spring for a new 36 for it. Thanks all for your responses.

nice work