Still MS170 chainsaw hard to start & doesn’t run long

[Burnerman]

This is how I set the idle, or slow running speed screw.
Get the machine running - use the mechanical throttle stop screw to achieve this if necessary, but have the machine running pretty slow - if it allows this!
Turning the idle screw in weakens the mixture.......the engine should speed up but it will have no power when you squeeze the throttle. Turning in too far will cause the engine to stall.
Turning the idle screw out makes the mixture richer.......the machine should start to slow up and maybe there will be a little smoke. Turn the screw back in at that point so the machine just starts to run slightly quicker and that should be it.
I hope this helps, but these carb settings are pretty critical!
John

 

[ipbr21054]

The screw on the carb is left hand thread.
I think you are talking about a normal screw

I am correct or wrong ?

 

[Burnerman]

I sort of remember this odd ball carb......does it have a funny slotted head?
No matter, turning it in weakens the mixture, turning it out riches it again.
Give what I’ve said a try and see what happens.....nothing to lose!
John

 

[ipbr21054]

Yes it’s a slotted screw.
So tomorrow I will get it warm then try in & out until I can rev it with the bogging & chains spinning in bar.

Thanks.

 

[ipbr21054]

So the question I haven’t asked yet is When I try to rev & it bogs down does that mean it’s not getting enough fuel ie I need to turn the idle screw out to make it richer.

Would that be correct.

 

[Burnerman]

It's usually not enough fuel, but unfortunately this syndrome can occur either way, and the machine still bogs down.
Experiment time, I'm afraid!
John

 

[ipbr21054]

Yesterday i started it & left it to run a few minutes to warm up.
I started to turn the screw a 1/4 of a turn & gave it a rev, i did this until i was able to rev without it bogging.
Even though these are a very good copy of the original something internal must be different slightly as i was turning it for a while until it was sweet.
Took the saw to the job where it performed fine & logs all cut up.

Many thanks.