# Stihl ms290 repair



## hlee (Apr 24, 2014)

Hello
This is my first post on this site. I was reading some of the dialog on rebuilding a stihl ms290 chainsaw. I just completed my rebuild by replacing a new piston /cylinder/carburetor/bearing and seals. The problem i am having is the saw will start but will not stay running. I have adjusted the carburetor but no success. i replaced all of the fuel line and filters in the tank but it still will bog down and stop. The only way it will run is if I take off the air cleaner and hold the choke barely open. If i open it to far it stalls out. If i try to squeeze the trigger it stalls out like it does not have enough gas. I took it to a stihl dealer and he adjusted the choke. I got it home and it ran for 5 minutes cutting and then stalled out again. I took off the air cleaner and it will run if I hold the choke barley open. It races at a high RPM if i do this but stalls out if i open the choke up and try to pull the trigger.
If anyone has any ideas or comments i would really appreciate any help.


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## 30yearTech (Sep 14, 2006)

You could possibly have a small air leak somewhere in the crankcase, intake manifold or fuel pump pulse hose. Did you replace the fuel filter?


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## hlee (Apr 24, 2014)

yes I did replace the fuel filter and new spark plug. Is there a way to check for a manifold air leak?
If i have a crankcase leak i would have to tear it completely down to re-seal it. I also thought it may be a intake boot leak. i did check it before I put it back on and was sure to use my fingers to push it through the plastic housing.


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## 30yearTech (Sep 14, 2006)

Other then a visual inspection, I have never heard of any test for the rubber manifold. I usually just check for cracks tears and pinholes, on both the mainifold and pulse hose.


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## hlee (Apr 24, 2014)

i did some more research and it looks like i was suppose to put gasket sealer on the oil seals. I only put gasket sealer on the cylinder.
I think i may have an exaust leak. I checked all of the rubber hoses and replaced them. They all seem to be OK but i still have the problem. I am not sure what to do at this point but to tear it down and re-seal and check everything again.


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## paulr44 (Oct 14, 2008)

The seals used during assembly are OFTEN different than used (by Stihl) on such type crankcases that split along crank centerline. The assembly seals have raised ribs to help provide a positive seal around the outside, while replacement seals don't which eases installation. Putting the sealant around the outside of the seal technically isn't crucial, but is an ounce of prevention.

What type of sealant did you use? Ultra-Black, Dirko? Whatever is has to be impervious to fuel, else it'll most likely fail and you'll have to tear it down again.

AS 30YR axiom imparts and to add on, "you have to know how it works before you can fix it," and to continue along that line, "you have to know why it failed before you can fix it" is why 30yr asks about the manifold etc.

Simple test - spray a bit of wd-40 and carb cleaner in the carb throat (with the throttle open) and try to start it. If it runs on this prime, you're most likely got an impulse or carb problem, although it could still be a vacuum leak.


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