oreo123

Hi all,
prob a stupid question to you but I cant work out what this screw does on the carburetor, the manual says nothing

BudBud

It is supposed to be a midrange adjustment.... it is the major weakness in that carburetor's design. Some people call it a needle, but actually it is an adjustable seat for the low speed needle. Almost everybody sets it flush and forgets it. They are secured by a couple of 0rings that are too small for the job and they turn easily when the rings get bad. The seat will start vibrating itself out and some guys have actually lost it. The best solution is to get some high temperature Permatex thread sealer, put a couple of drop on the threads and set it flush. As the screw goes back in, I paint the edge of the screw head with RTV and then wipe off the excess after it is set flush.

Glen

twomanytoys

Thats a set it and leave it screw. It will cause more grief trying to tune it than just to leave it alone. Tune the low and high needle and thats it.

oreo123

do you know what the factory setting is for it?

BudBud

Flush, the face of the screw should be flush with the carb body, seriously tough, get some Permatex number 59214 and seal the threads with it. You will wish you had when it starts dancing around on its own. Glen

oreo123

would some thread lock work?, also, do you know the factory settings for the Hsn and the Lsn?

3-172IN MTN

If you want factory settings set the needles flush.

mopartybob

I was also plagued by this screw's tendency to walk around it's set it and forget it setting..... [:@] [:'(] , after searching MANY threads for the answer to your question, of which i asked and posted myself, I found that you remove the Hi-speed needle assy,and look down the bore of the housing,line up one of the (4) metering holes with the open hole in the HSN bore, the face of the mid-range range needle should be as close to flush with the housing as possible,but still keeping the metering hole fully exposed, ...RTV that face with the housing and never touch it again.... thats why there is no info in the manual about it.....once you start screwing with that screw,your screwed... [:-]

BudBud

A lot of guys have completely lost that screw while running, some guys found out that when you turn the lsn, that screw turns too, and no matter what you do, the tune never gets right. It is a really bad design, but they have stuck with it.

Savage SS BEAST

Iv had that needle blow out before while i was running the truck not even jumping it just driving it around HPI sent me a new one

BudBud

What a PITA though, it looks like they would have recognized the problem and changed the design by now. When they are all sealed up, they do work fairly well. [] Glen