...okay, i'm gonna fess-up here...my main jet is actually a Kehin...it's threads were not a perfect match to the holder's threads...
..but that's the neat thing about brass...it's millable, and can be forced to comply to your will fairly easily...
..the threads would start..for about 3/4 of a turn, maybe a little more, then would begin to lock up..
..so, i broke out the thread lube and a cpl of wrenches..lubed it up real well and began to work the jet in and out of the holder, turning it in a little further each time...this generated heat, so i had to cool it from time to time..
..with a little patience, and a lotta lube, i was able to mold the two threads together..
..the other thing about the Kehin jet is that it was a bit longer than my original..(which i seem to have lost)..too long as a matter of fact, and I had to shave quite a bit off of it's head to get sufficient clearance between it and the carb's bowl...
..don't know if you want to try this, but if the threads will start, and you go slow, it should work...
peace