Chainsaw Not Revving

Mach Two

I have a Stihl MS180c. This saw has been working good and bad intermittently. It was working perfectly last week. Now when I rev it it dies. And would probably stop if I don't release the accelerator. Air filter has been cleaned. Same problem when I take off the bar and chain. Any suggestions welcome. Sounds like a carburetor problem. It is a small saw with a 12" or 14" bar.

philog

Mach Two wrote: »

I have a Stihl MS180c. This saw has been working good and bad intermittently. It was working perfectly last week. Now when I rev it it dies. And would probably stop if I don't release the accelerator. Air filter has been cleaned. Same problem when I take off the bar and chain. Any suggestions welcome. Sounds like a carburetor problem. It is a small saw with a 12" or 14" bar.

Take the spark arrest or out of the muffler .. clean it or throw it away

philog

philog wrote: »

Take the spark arrest or out of the muffler .. clean it or throw it away

Hold your horses...

Fuel filter first.

Mach Two

JayZeus wrote: »

Hold your horses...

Fuel filter first.

Fuel filter seems to be ok.

Mach Two

philog wrote: »

Take the spark arrest or out of the muffler .. clean it or throw it away

What is a "spark arrest". Never heard of one but by the sound of it it stops sparks from coming off the exhaust.

Mach Two

It seems to be working alright again today. But only to start acting up again I expect.

Mach Two

Ok. I have taken the cover off the exhaust and I can see the spark arrestor. It is actually part of the exhaust so I can't throw it away. It looks perfectly clean. The holes are completely open. The air filter has been cleaned so I expect that is ok. I rechecked the fuel filter and that looks perfectly clean.

Mach Two

Anymore suggestions on this.

bonzodog2

Check the gap etc on the sparkplug

MrFireCoalMan

Had the exact same thing on a strimmer recently. Worked fine one week, then this the next. Small adjustment to the high speed mixture screw on the carb was all that was needed. YouTube will have what you need.

Rows Grower

Mach Two wrote: »

Anymore suggestions on this.

Get youtubeing if you decide it's a carburetor problem.

Friend of mine had exact same problems with a small stihl, handed it in to tool hire/repair crowd. They rang him today, it's a carburetor problem they said, 150 euro to fix.

Before giving it in anywhere, check that the fuel tank breather is working, or just replace it with a new one. Should cost you buttons for the part. If the breather isn't working properly, there will be a vacuum in the fuel tank which will starve the carb when you rev it up. If you're careful (remove the chain, leave the bar on and put the clutch/brake cover back on, you'll be able to lay the saw on its side when it's acting up/bogging down while it's running and just loosen the fuel filler cap a bit. If the breather hasn't worked right and there's a vacuum, loosening the cap a bit should let the saw rev up properly, proving to an extent that the breather's at fault. It happens.

Melodeon

Check the rubber pipe from tank to carb isn't kinked or collapsed or otherwise restricted, or collapsing when the engine is running.

Rows Grower

JayZeus wrote: »

Before giving it in anywhere, check that the fuel tank breather is working, or just replace it with a new one. Should cost you buttons for the part. If the breather isn't working properly, there will be a vacuum in the fuel tank which will starve the carb when you rev it up. If you're careful (remove the chain, leave the bar on and put the clutch/brake cover back on, you'll be able to lay the saw on its side when it's acting up/bogging down while it's running and just loosen the fuel filler cap a bit. If the breather hasn't worked right and there's a vacuum, loosening the cap a bit should let the saw rev up properly, proving to an extent that the breather's at fault. It happens.

Fair play, you know what you are talking about.

Rows Grower

Rows Grower wrote: »

Fair play, you know what you are talking about.

Ah sure, it's good to give the benefit of my own experience is all I'd say. I wasted the price of a new Walbro carb on a Husky 242 (fughnfughnfurgh)before I copped the new breather I'd fitted (spurious) when I rebuilt the saw had a ball valve that was sticking on it. Not to mention the carb kit and ultrasonic cleaner I spent money on before I bought the new carb.

Just wasn't thinking right, so nowadays it's the simple stuff first and not a euro spent before I've spent time picking through the troubleshooting steps properly, even if I think it's unlikely. Too easy throwing money into something that only needs a bit of a cleaning, adjustment or a €2 part replaced. Step by step and don't skip any will often lead you right to the problem.

Ten Pin

Fuel filter might look OK but if it's a cotton filter it might work OK on idle but not when revved if it's clogged. If the saw is left for an hour, the filter will soak up fuel and be fine at first start but then cut out as the filter won't allow higher flow.

Then check tank breather (as mentioned above)

Then check fuel line for cracks, if it's cracked inside the tank it will just end up drawing air instead of fuel. To check this, fill the tank to the very top and see if saw runs OK (no air to draw).

Then it's a matter of taking off the carb and carefully opening it to check the diaphragm and fuel inlet gauze/screen. Take pics as you go so you know how to reassemble.

Mach Two

A lot of really great tips there. Really appreciate all of your commits.