Saw and blower problems...

[Little Butch]

Got given an ms170 which apparently didn't run. After some fresh fuel it fired up perfectly and after a while it eventually revved up fine. Used it cutting some oak up for my parents a couple of days ago and it ran perfectly for about 15 minutes, then slowly the revs lowered and it died. If you let it rest for a bit it will eventually start and do the same again... Any ideas what this could be?

 

I've also got an old stihl blower, runs okay as long as you keep pumping the primer while it's running. What could this be? Blocked jet or something? Perished pipe?

[Stubby]

Saw is possibly low comp . caused by wear/previously light seize in the piston and cylinder . starts and runs initially then as things warm up and expand clearances become wider and comp drops off to below whats needed for combustion .

[Little Butch]

Thanks for he quick reply stubby! Somebody else had mentioned that and it does make sense. It's a 2007 saw I think but looks like it's not done much work. Maybe run with a wrong mix of fuel?

[spudulike]

Pop the muffler off and look for scoring to the piston, should be obvious if it is damaged.

 

The blower will need the metering arm lifting 0.5mm or a new diaphragm in the metering section of the carb going on your description.

[Little Butch]

I'll whip the muffler off and check that tomorrow. Okay I'll look into that. Carb will probably need a good clear out anyway judging by the state of the blower! Got it cheap though so can't complain if I can get it running properly.

 

Cheers!

[Little Butch]

Whipped the exhaust off, pulled it over slowly so I could see the piston properly, didn't notice anything abnormal, rings looked okay too. So what's next lol?

[Stubby]

Whipped the exhaust off, pulled it over slowly so I could see the piston properly, didn't notice anything abnormal, rings looked okay too. So what's next lol?

 

Could be a blocked tank breather . Eventual sucks a vacuum . Try cleaning / or fitting a new breather .

[Little Butch]

Never heard of a tank breather, where can I find this lol?

[spudulike]

Whipped the exhaust off, pulled it over slowly so I could see the piston properly, didn't notice anything abnormal, rings looked okay too. So what's next lol?

 

Just strip the carb and clean it and reset the metering arm

Quite often it is all they need!

[Little Butch]

I've got Friday off so I think a day of tinkering is in order. I'll take the carb off both the 170 and blower and see if that solved anything. Thanks for your help