stihl restoring

danny23

Hi, I have changed cylinder set in my MS 390 but I used new set for 290 model(aftermarket), there is one problem, i cant set carburetor. Is necessary to change jetts?
New sealings in engine, new carb membrane, nedle valve, clean air filter......
Thanks

CJR72

G,day done that myself and according to the ipl there is a different jet, its listed as the high altidude jet, but i went down to the local stihl dealer and was told that the 290 through to 390 run the same carb and jet size here in australia ,sounds like you might have another issue if you can't tune it,did u do a vac test on it after assembly?

danny23

No, i did not do vac test. How to do it? Do you think there is some air getting? Where coluld be possible place of air inlet? I have tuned needle valve lift in carburetor cca 5 times, it seems still too much fuel gets into engine. H screw must be more than 1 turn off, im affraid when too lean mix leads to overheat and destruction of cylinder and piston. And at H screw is o-ring sealing missing, could affect this? When ran saw first time after new cylid.set, it went nice, good performance, sound, fast gets in high rpm. After 3 - 4 fuel tank burned out, started problems: turning off, irregular running. Compression stil good