The Forestry Forum

General Forestry => Chainsaws => Topic started by: otherguy on June 11, 2017, 05:19:27 PM

Title: Stihl MS 660 not start when hot
Post by: otherguy on June 11, 2017, 05:19:27 PM
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
Title: Re: Stihl MS 660 not start when hot
Post by: joe_indi on June 12, 2017, 01:10:36 AM
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
Title: Re: Stihl MS 660 not start when hot
Post by: Texas-Jim on June 14, 2017, 10:03:13 AM
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.
Title: Re: Stihl MS 660 not start when hot
Post by: HolmenTree on June 14, 2017, 10:45:07 PM
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.
Title: Re: Stihl MS 660 not start when hot
Post by: Al_Smith on June 15, 2017, 05:57:02 AM
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 .
Title: Re: Stihl MS 660 not start when hot
Post by: limbwood on June 15, 2017, 04:55:41 PM
my buddy has a 395 that did that he put the next cooler plug in it and hasnt done it since.
Title: Re: Stihl MS 660 not start when hot
Post by: Canadiana on June 15, 2017, 07:48:26 PM
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.
Title: Re: Stihl MS 660 not start when hot
Post by: limbwood on June 16, 2017, 09:17:43 AM
the regular plug is a ngk bpmr7a, you would need a bpmr6a i think.
Title: Re: Stihl MS 660 not start when hot
Post by: HolmenTree on June 16, 2017, 07:17:55 PM
You can get a colder one like a Bosch WSR5
Title: Re: Stihl MS 660 not start when hot
Post by: CTYank on June 20, 2017, 07:25:43 AM
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.)