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Stihl MS 660 not start when hot

Started by otherguy, June 11, 2017, 05:19:27 PM

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otherguy

I was cutting this weekend and the first few times it started just fine but the weather got warmer and at some point the saw wouldn't start unless I let it cool for 20-30 minutes.   After that would start fine and run but if I turned it off even after one cut I had to let it rest.

I have never ran a saw in these temperatures but this was a special circumstance, even then the temp was just 80-85.

Just wondering what to look at our what to do.
Thanks

joe_indi

Partially blocked pickup body could be the cause.
The fuel pump has to work harder to suck fuel.
The higher temperature and extra vacuum created by the partial block could cause 'boiling' of the fuel in the lines.
Try replacing the pickup body and also check the strainer at the bottom, pump side of the carb.
Check the tank's air vent also

Texas-Jim

Were you trying to start it at idle? As a rule hot saws do start better in the fast idle setting, stihl even tells you start it there.
What we do in life echoes through eternity.

HolmenTree

Could be the ignition module is breaking down.
My other advice without seeing it is check to see if the winter preheater shutter in the top cover partition is open allowing cylinder heat back to the air box.
Also check the cylinder fins if their dirty.
Making a living with a saw since age 16.

Al_Smith

For some reason often hard starters when heated up will respond better to a wide open throttle start up .Why I have no idea .
It might help if on shut down you give it a little cool down run prior to hitting the kill switch .Could be the solid state ignition system .

limbwood

my buddy has a 395 that did that he put the next cooler plug in it and hasnt done it since.

Canadiana

Hey limbwood, what is a "cooler plug?"  A few of the local auto mechanics i talked to avoided using champion plugs. They're colleagues and don't recommend a prefered brand just not the champion. I've been going with ngk. They seem fine. Bosch lasted good too. Ive no preference.
The saw is more fun than the purpose of the wood... the forest is trembling 🌳

limbwood

the regular plug is a ngk bpmr7a, you would need a bpmr6a i think.

HolmenTree

You can get a colder one like a Bosch WSR5
Making a living with a saw since age 16.

CTYank

Quote from: limbwood on June 16, 2017, 09:17:43 AM
the regular plug is a ngk bpmr7a, you would need a bpmr6a i think.
Nooooo, not if you want to go a step colder. With champions, smaller # means colder. The OPPOSITE with NGK- larger # means colder. Wouldn't want anyone to hole a piston here. (bpmr8a would be candidate.)
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