Weird ms170 issue

[Sagaris650]

I’ve got a problem with my ms170. It doesn’t idle very well all the time but when I manage to get it to it will die when I pull the trigger while I’m holding it. The weird thing is if I pull the trigger while it’s on the floor it revs fine. 
what would cause it to work properly when it’s on solid ground opposed to holding it in the air? When I hold it I have it in the exact position as it is when it’s on The floor as well. 
 

I’ve put on a brand new carb, air/fuel filter, using brand new aspen fuel and a brand new spark plug. The only thing I’ve noticed about the spark plug is half of it is brown and the other half is black. 
Does it sound like I need new crank seals? 
 

Thanks James
 

 

[openspaceman]

4 hours ago, Sagaris650 said:

The weird thing is if I pull the trigger while it’s on the floor it revs fine. 
what would cause it to work properly when it’s on solid ground opposed to holding it in the air?

AV mounts flexing and affecting the throttle linkage?

 

Strange mechanical things can happen; I had a saw on which the choke would only engage if it was held vertical, problem was a loose choke butterfly screw letting the butterfly drop and jam against the carburetor when horizontal.

[Sagaris650]

I was thinking a mount or a vibration issue. I don’t think it’s a throttle issue because the carb opens and closes fine on the floor or in the air. The saw is struggling to rev like it’s a fuel or air problem but I don’t get why revving the saw on the floor works opposed to when I’m holding it in the air. 

[Stubby]

1 minute ago, Sagaris650 said:

I was thinking a mount or a vibration issue. I don’t think it’s a throttle issue because the carb opens and closes fine on the floor or in the air. The saw is struggling to rev like it’s a fuel or air problem but I don’t get why revving the saw on the floor works opposed to when I’m holding it in the air. 

Could be split fuel line or intake boot that stretches slightly when the saw is moved on its AV . 

[Doug Tait]

Had a saw which would start and idle no problems hanging on a harness but cut out when turned on its side due to impulse line.

[Sagaris650]

What is an impulse line? I will check this as well. Cheers

Edited April 14, 2023 by Sagaris650

[Sagaris650]

1 hour ago, Stubby said:

Could be split fuel line or intake boot that stretches slightly when the saw is moved on its AV . 

Ok I will check that. I did change the fuel line but it wasn’t genuine. 

[Doug Tait]

1 hour ago, Sagaris650 said:

What is an impulse line? I will check this as well. Cheers

 

This might help explain better than I can, I only know it was an issue because the dealer told me when I paid them!

 

https://arbtalk.co.uk/forums/topic/113185-impulse-hose/

[Sagaris650]

I think I might of found the problem. I stripped the saw down and the rubber part that connects the carb to the engine had a bent bit f tube where it’s meant to go to the carb for fuel suction. 

[Stubby]

6 hours ago, Sagaris650 said:

I think I might of found the problem. I stripped the saw down and the rubber part that connects the carb to the engine had a bent bit f tube where it’s meant to go to the carb for fuel suction. 

That intake boot might be split because of that .