Chainsaw problems.

[Ton-up]

Hello all,
I have a Stihl MS170 chainsaw that I use a few times a year. I was using it a few days ago, and after about an our of use, with no problems, it suddenly lost power when cutting.
The saw starts, ticks over and rev's fine (maybe a bit less max rev's than normal, but hard to tell) but as soon as you put the chain on wood, it bogs and the clutch slips, and engine carries on running slowly.
The chain is fine and I have swapped the chain, bar, spark plug and the have taken the carb off, cleaned it out and still no difference. I then emptied the fuel tank and refilled it with new fuel mix. Then changed the carb for another good one I had.
Still the same, lack of power.
So, any suggestions where to go from here please!

 

[wristpin]

Possibly a dodgy coil/electronic gizmo.

 

[TomCGB]

Sounds like it could be the muffler. Its quite common for the spark arrestor to get clogged up.

 

[Migmac]

Change the fuel filter and clean the air filter

 

[pedrobedro]

Strip and clean the carb and check the fuel pipe, don't leave old fuel in as it gums them up and rots rubbers with the ethanol content. I had to put new diaphragms in my old Dynamac for the same reason. Start the saw at knock off then stop it and tip the fuel into something then start it and let it tick over till it runs out. It seems wasteful but it is better for the saw.

 

[Ton-up]

Sounds like it could be the muffler. Its quite common for the spark arrestor to get clogged up.

Tom, your'e a legend , and I feel like a pratt!!! It was the muffler holes underneath the outer louvred plate that were nearly all blocked. In my defence, being annoyed with it, I had stopped for my dinner and wrote the question, but a blocked exhaust is basics!!

Thanks again.

 

[TomCGB]

No worries. Glad you've got it sorted.

 

[rich r]

I've had exactly the same on my MS180 (almost the same as an MS170). And yes, it was a blocked spark arrestor mesh in the muffler too. I've also had similar symptoms due to a blocked air filter. Would start and run fine with the orange cover off, but bog down or even stall if the cover's fitted and it's asked to actually cut anything.

 

[balmerchris]

Pull the muffler off and port it while your at it.

 

[The_Yellow_Ardvark]

When that happened to mine, I had a husky what the silencer would bung up. In the end ran it with the guts ripped out.
In the middle of no were who cares.
End of the day if it got to bad I would burn it out.
Pop it off, Oxy acc kit heat it up red heat, then reduce the gas and increase the O2. It would then burn back all the crap off.