Hi all, my first post to this forum. I have a Stihl Ms361. It always starts 3rd pull, when it starts it runs at full throttle for 5-7 seconds and then quickly dies. I've replaced the carb and the coil, also have removed the fuel filter. When replacing the carb, I checked to make sure I could blow through the fuel hose, so no blockages. I'm wondering if this could be a compression problem, but when pulling it over its not an easy pull unless I use the compression release. Any suggestions would be appreciated.
Ms361 starts but stalls quickly
- Thread starter keitha
- Start date
My guess would be- the saw has a massive air leak- likely a torn manifold between carb and cylinder.
This will allow for a huge change of the air to fuel vapour ratio, meaning the mix is extremely lean and causing the high revs when the saw is set at idle and you are not activating the trigger. Then it sucks enough air in to over rule any fuel in the combustion chamber and dies.
If it starts on the third pull I might suggest you still have compression- but if you continue to start it and allow it to free rev- you wont for long and be costing yourself a new piston and possibly cylinder as well.
Pull the muffler, look at he piston through the exhaust port and see if it is cutting up already.
If you have the tooling and knowhow- do a pressure and vacuum test on the saw now!
If you do not, take it to a shop and have them do it.
Manifold is my most likely guess- but it could be main crank seals.
This will allow for a huge change of the air to fuel vapour ratio, meaning the mix is extremely lean and causing the high revs when the saw is set at idle and you are not activating the trigger. Then it sucks enough air in to over rule any fuel in the combustion chamber and dies.
If it starts on the third pull I might suggest you still have compression- but if you continue to start it and allow it to free rev- you wont for long and be costing yourself a new piston and possibly cylinder as well.
Pull the muffler, look at he piston through the exhaust port and see if it is cutting up already.
If you have the tooling and knowhow- do a pressure and vacuum test on the saw now!
If you do not, take it to a shop and have them do it.
Manifold is my most likely guess- but it could be main crank seals.
Hi Bob,
I made an error in my description, it only revs high when I engage the throttle. I was saying that it runs very well for a couple of seconds, and then shuts down. Now that I say that, I've not tried to start it and just let it idle. When the problem first started, I was thinking I had a clogged jet etc nd was running at high speed to see if i could keep it going. Sorry about that.
I made an error in my description, it only revs high when I engage the throttle. I was saying that it runs very well for a couple of seconds, and then shuts down. Now that I say that, I've not tried to start it and just let it idle. When the problem first started, I was thinking I had a clogged jet etc nd was running at high speed to see if i could keep it going. Sorry about that.
So it starts- idles, but when you pull the trigger it screams up into high revs and dies?
Still an air leak is my guess- could be manifold or main crank seals. Pressure and vacuum test will diagnose- but if it will idle you can spray brake clean around the exposed clutch, flywheel areas to check for seal leaks and around the manifold for leaks there- if they are present- the saw should stop running as it sucks in the brake clean spray.
Still an air leak is my guess- could be manifold or main crank seals. Pressure and vacuum test will diagnose- but if it will idle you can spray brake clean around the exposed clutch, flywheel areas to check for seal leaks and around the manifold for leaks there- if they are present- the saw should stop running as it sucks in the brake clean spray.
Start with pressure- should hold 7lb for a good long while.
If it passes that- say sits at 7lb for 5 minutes- (I doubt it will) then go to vacuum test but do not exceed .4-.6 BAR or 11.8-17.7 in-Hg.