M carb questions?

[4520BW]

The main adjust screw hole in back side of bowl, what is the thread size? I need to chase the threads. Also what are thread size on the needle? (Just curious,) thanks!

 

[DanielW]

Can't help you on the thread size, but are you sure you have to chase it and it's not just the lead packing you're looking at? You probably know this already, but around that main jet there's a lead packing: You tighten the bung nut on to 'squish' the lead around and against the jet once it's in there, and it will (kind of) mold itself into the threads. If that's what you're looking at, the 'threads' will certainly look pretty ugly, but that's because you're just looking at the lead where it (kind of) molded itself into the threads. The true 'threads' are deeper in. You can usually just get the jet threaded down into the true base threads and the lead will deform accordingly, then tighten up the bung nut some to squish the lead packing a little more. You can get new rubber packing, but the old lead stuff can usually be re-used (I don't even take it out when I do a carb with it).

Again, you probably know all this already, but if not take a look at this part of this video:

 

[4520BW]

When I took it apart to rebuild it was cross threaded and lots of tape on it.

 

[BarnyardEngineering]

When I took it apart to rebuild it was cross threaded and lots of tape on it.

Ouch. Chasing the thread isn't going to fix that...