T540xp cutting out.

[Mark_Skyland]

Having a bit of an issue with a 540. It will idle fine but the revs drop too low and it cuts out of you let go of the throttle while under load. No issue if you let go of the throttle while not cutting.

 

Tried lots of things so just wondering what the most common faulty component would cause this issue?

 

Pressure and vacuum fine, good compression including new piston ring. Plug and coil gaps fine, tried swapping coil and carb from other 540

but still no good, no faults on autotune and wiring all good, also tank vent and pipes all good. Never had this much trouble with a machine before!

 

 

 

[Stubby]

Electronic fuel valve possibly .  (Not split impulse line as you say all pipe work is ok ).

[Husqvarna King]

Is the throttle cable correct ( to right of filter), I must have knocked mine when cleaning out once on my MK1. Took me half hour to spot what was wrong. Wouldn't run right. Just a thought

Edited November 18, 2018 by Husqvarna King

[adw]

As with any auto tune saw lack of compression effects the idle first, i think i would have put a piston into it rather than a ring, have seen excessive ring wear on a number of T540s

[spudulike]

As ADW said, the autotune likes a perfect engine and doesn't take wear and tear as a friend. Expect any wear in the engine to cause idling issues like this. It is a shame you cant raise the idle speed but guess it will breach the emissions the machine is certified to produce....give me a standard carb any day!

If the machine marks on the piston have smoothed then it is usually best just to fit a new piston as the saw is a bit of a bitch to strip down in my humble opinion!

[Mark_Skyland]

Cheers for the replies.

 

Noo problem with the throttle cable or linkage. Changing the ring has sorted out a few saws that had idling issues but they struggled to idle all the time, this one only struggles to idle after the throttle is shut under load. So I thought it a long shot but I had already tried most things. True about them being a bit of a bitch to strip down! Tbh there was hardly any wear on the ring and since the operator has been using aspen the engine was spotless. 

 

I should of added that there are no issues that I can see with the drive train. The time I have spent on this machine would probably run a labour charge close enough to that of a new saw but since I won't be charging the customer anywhere near that much I might strip it back down and check the piston out. Shame not to get it sorted now.

[spudulike]

And that's the way it goes sometimes, hopefully the next five on the bench will go smoothly and make up for one saw that just saps time. Been there and sympathise!

[adw]

Did you manage to sort this??

[Mark_Skyland]

Not yet unfortunately. Might try the new piston kit route.