Stihl 660 started idling high now quit running

My Stihl 660 randomly started idling a bit it didn’t seem like a big deal, I just figured I needed to adjust the carb. I kept cutting and the saw reved high like it was running out of gas and quit running. It still had about a quarter tank of gas. I let the saw cool down and now it won’t start at all. it has plenty of compression.

I’m figuring an air leak? Could it be the fuel filter? Where should I start checking for an air leak?

 

Pull the muffler/muffler cover and take a pic of the piston and ring(s). Post it here. If it developed an air leak, there could be scoring on that piston, and on the cylinder wall. I wouldn’t try starting it again till you see for sure. Could do more damage.

 

Classic air leak signs. Check the hoses, intake and crank seals.

 

This!

 

Thanks, I’ll pull the muffler and take a look. Might be a couple days before I get a chance to get at it. I’ll report back

 

I pulled the muffler quick and good news the p and C look good. Looks like an easy fix, but how the heck do I get at the bolts to tighten them?

 

WOW...
There should be 4 access holes starting at the top of the cylinder. Most likely torx head screws.

 

Glad it's an easy fix, but I haven't seen bolts back out that much on a cylinder before. That's pretty wild.

 

Do I take the plastic covers off first?

 

Yes. The air filter plastic, then the top plastic. It has 3 or 4 screws holding it on. I don't remember without looking.

 

Wait a minute here....I thought only Husqvarna had screws / bolts come loose. At least thats what the internet says.

Joking aside, I'm glad you didn't end up with a damaged engine from this. Luckily the air leak was so large and quick there wasn't enough time to melt down.

 

Thanks 2 more questions.

do the bolts need to be set at a certain torque?

should I use loctite on the bolts?

 

I’d pull the loose ones out, one at a time, loctite and re install just snug to a little more than snug. Then pull the back two, one at a time and loctite and reinstall, a little more than snug
Then cross pattern tighten incrementally. With a T handle, until the shaft starts to twist. I’m sure there is a torque value you could find if you want to go with thst

 

Blue loctite will be sufficient. Make sure no sawdust boogers get in there.

 

Thats pretty much how I do it after using brake cleaner on the holes and bolts.

 

You ever use the Loctite primer? It makes a big difference...I had never heard of it until one of the machinists at work was talking about it...we tried it on some 3/4" studs that we were having issues keeping things tight, it took "locked" to a whole nother level! (it doesn't make the Loctite stronger, but it promotes adhesion, and speeds curing, big time!)
Loctite Klean 'N Prime Adhesive Activator 4.5 oz NCB 37509 | Buy Online - NAPA Auto Parts

 

I have not. Thank you for the information.

 

Not to cause you more work, but trying to prevent issues down the road. I’d be concerned about sawdust getting sucked into the base gasket area with only a metal base gasket. If it were me I would clean it up as good as I could, remove the cylinder, clean the area, and then bolt it back down

 

You can pretty much tighten them all you can get out of a T handle. They are M6 where most others are M5