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Author Topic: MS290 won't run slow  (Read 1552 times)

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Offline jvh24521

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MS290 won't run slow
« on: March 04, 2014, 04:43:46 pm »
Greetings,
I had been using my saw all day. Started cutting a large standing tree and suddenly it would not run unless the throttle was wide open or nearly so.

It will start in the choked position and then if I can get it started in fast idle and rev it up it will stay lit but it will not run slow.

Fuel and impulse lines are OK. Impulse stem on block is open too. Cleaned the carb, put in a kit, new fuel filter, and screen too. Same problem, just seems like it is not pulling in the fuel since it has to be choked or high RPM.

John, aka, Sixty and stumped.
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Offline jmester

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Re: MS290 won't run slow
« Reply #1 on: March 04, 2014, 05:06:35 pm »
Pull the muffler and look and see if you have some scoring or seize marks on the piston. Could have ran lean today for how cold it was.
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FEAR NO TREE. FEAR GOD.

Offline jmester

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Re: MS290 won't run slow
« Reply #2 on: March 04, 2014, 05:11:03 pm »
What makes me say that is, had a 660 do that to me before I knew anything about chainsaws and did the same thing you did. Then took it to a shop and they said the piston was scored from a lean seizure. Hope it is not the case.
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Offline roostersgt

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Re: MS290 won't run slow
« Reply #3 on: March 04, 2014, 05:21:35 pm »
How about checking the muffler outlet and screen? Might be clogged.
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Offline Cut4fun

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Re: MS290 won't run slow
« Reply #4 on: March 04, 2014, 06:52:36 pm »
WAG what about tank vent?  If it was stopped blocked up with crud would or could it maybe cause this?
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Offline jmester

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Re: MS290 won't run slow
« Reply #5 on: March 04, 2014, 09:07:00 pm »
The only other thing I could think is the primary or secondary idle jet is clogged in the carb. But don't think that as he said he cleaned it and the saw will start with the choke on. And if they where it would be real lean on the high side. If it is a faulty vent I don't think he would be able to get it started as the vent releases the pressure in the tank as to not vapor lock. Once they build pressure in the tank it is hard for the pump to get any fuel up the line to the carb.
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Offline 3000 FPS

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Re: MS290 won't run slow
« Reply #6 on: March 04, 2014, 10:38:43 pm »
Look for scoring on the cylinder and then I would check for an air leak.    The carburetor is pulling fuel or else it would not start and run at all.   Sounds like it is very lean from a bad air leak.
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Offline AKDoug

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Re: MS290 won't run slow
« Reply #7 on: March 05, 2014, 01:15:03 am »
Very likely a bad air leak. You can't run at low RPM's because you have too much air for the mixture. When you are adding fuel it is able to run, but it is likely running very lean. Do not run the saw anymore until you thoroughly check out the saw. It needs to be vacuum/pressure checked.
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Offline stihls066

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Re: MS290 won't run slow
« Reply #8 on: March 05, 2014, 02:11:49 am »
Clutch issue is possibility. Had a 066 that stopped idling because a bad spring
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Offline 3000 FPS

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Re: MS290 won't run slow
« Reply #9 on: March 05, 2014, 09:55:21 am »
Quote from: stihls066 on March 05, 2014, 02:11:49 am
Clutch issue is possibility. Had a 066 that stopped idling because a bad spring


You can pull the bar and chain off and start it.    If a bad clutch spring it will run and idle without the bar and chain attached.
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