High screw almost in but still rich

[Stergos Rodos]

Hello to everyone! I have a jonsered 670 champ. I m trying to find the reason it is running rich even with the high screw in. The saw has new meteor piston, new fuel lines, new muffler, new diaphragms. Tillotson hs series. Service manual says welch plug or nozzle valve leaking. This has not a welch plug but a main nozzle valve. I have to test if it works well and if it seals. Any suggestions ?

 

[heimannm]

To test the High Speed check valve, I just press the square end of a piece of tubing against the brass nozzle body and alternately suck and blow. It should pass when you blow and hold when you suck.

Too rich with the H jet mostly closed could also be the metering lever set incorrectly or the metering diaphragm (assuming you changed it) has the wrong projection on the nub that presses the metering lever. If it were way off the carburetor would not hold pressure and the saw would be prone to flooding even when switched off.

Mark

 

[Kenskip1]

Is the choke all the way open? How about a partially clogged air filter? Just the basics but you have to start some place. Could the choke be slightly closing during high speed operation?

 

[Ozhoo]

Can also be caused be your metering diaphragm not being hooked into the control level. One of those Tilly HS things that people often overlook.