The Stihl thread

@Eccentric Aaron , the needle will hold pressure to about20 psi . But , once it pops and relieves pressure , it will not reset ,and leaks down . I’ve cleaned the seat , changed needles , tried a different spring . Still the same stuff going on . Any ideas ? ? ?

@Nixon
Did you set the lever height? Do you have the gasket against the carb body with the diaphragm on top of that? On the metering lever, if the diaphragm end of it is forked, did you make certain that the fork fits in the groove of the 'tit' on the diaphragm center plate? Odd that it holds once and then won't reseal....
 
@Nixon
Did you set the lever height? Do you have the gasket against the carb body with the diaphragm on top of that? On the metering lever, if the diaphragm end of it is forked, did you make certain that the fork fits in the groove of the 'tit' on the diaphragm center plate? Odd that it holds once and then won't reseal....
Metering lever is perfect . The gaskets are in the prper order . It has the normal button / lever set up , not the one like on some of the older tillies . Not sure what to do here . . .
 
Turn the needle 45 degrees and pressure test again?
have used 2 new needles . May try figuring a way to polish and lap the needle seat ,and bore . Sure would be nice to figure this out .:cowdance:
may stretch an old spring just to see what happens . Is the a max pressure for pop off that if you go too far beyond your saw ‘splodes ? .
 
have used 2 new needles . May try figuring a way to polish and lap the needle seat ,and bore . Sure would be nice to figure this out .:cowdance:
To me it sounds like the corner of the needle is getting stuck in the crotch of the fork, or hanging up on the edge of the bore. Or something weird. When you install all that shit I assume you give it s little flick of the lever, so it seats. Try lowering the leaver slow to see if it hangs up, you can watch it as you put the air to it?
 
When you get to the 'its the point' of the deal, rather than just making it go, you get into this territory.

Been there.

Toothpaste and a drill, spin a longer needle in it. If its a long one, may have to do it manually. (T one dated girls equipped like this)

Got to make sure all the passages are clear, air has to move as well. Some times its a check valve shot, and thats a replacement deal, too.

New/different carb failing that.
 
Haven’t timed it . But once it pops off @ about 20, the drop is relatively fast ,and steady down to about 5 . And , when you raise the pressure back to 20 ,it doesn’t pop off ,it just drops steadily as if the needle hasn’t seated properly .
And it holds under 5 or does it drop at a slower rate?