Husqvarna 136 Chain Turns at Idle

[rollingreenhills]

I have a 10 year old husqvarna 136 which I have owned for 3 years and done 2 seasons worth of firewood.

 

The chain turns when the saw idles, I used to put on the chain break but now it revs so high the chain break will not hold it.

 

I have changed the diaphragms and other soft parts in the carb, and I have adjusted the idle screw ALL the way out, the low jet is set the the point where the saw chokes and dies, but yet the chain still moves at idle.

 

I have also tighten the clutch spring, but the saw is obviously revving way higher than it should so I do not think it is a clutch problem.

 

I would appreciate any pointers.

[Dan Forsh]

High revving for no apparent reason usually points to an air leak. You need to stop using it and have it pressure and vac tested before it does significant damage.

[rollingreenhills]

So is this air leaking in to the combustion side of the carb, or a worn (?) piston or something.

 

I have purchased a replacement saw ( a husq 545) but I would like to repair this is possible.

 

Thanks for your reply.

[spudulike]

You say that increasing the L screw mix so the saw is almost dying still causes the chain to spin and then say that you can't get the revs down????

 

A classic way of dropping revs on idle when there is an airleak is doing just this but if the chain still spins at low revs then the clutch spring is bad or something is binding between the clutch drum and clutch/crankshaft.

 

You also say the chain brake won't hold the chain stationary any more - this is designed to snap the saw back to stop when running flat out so it sounds like this needs attention as well!

 

It is possible the throttle is being held open a little or the throttle valve isn't closing well - try running it up with the top cover off and locate the throttle arm on the throttle valve and close it with your finger or screwdriver and see if it brings the revs down a bit.

 

The saw over revving needs to be sorted so the idle is correct - Under 3,000rpm and if the chain still spins, the clutch and drum need stripping, cleaning and lubricating.

[adw]

Just pull the carb off and make sure the throttle butterfly screw has not come loose, make sure it closes fully in the carb, whilst the carb is off check the rubber inlet tube and purge tube behind the carb mounting block have not split, it does happen on older machines

[peatff]

Take the clutch off and look at the oil pump drive if the clutch springs are not shot.

[rollingreenhills]

Wow. Thanks for all of the tips guys. I really appreciate it.

 

The chain will stop by riching up the low jet, but pretty soon after the saw stalls.

 

I have changed the clutch assembly, and replaced the sprocket (and bearings) without it rectifying this problem.

 

I have also used a torch to look inside the carb, and can see that the round flap fits snugly in the aperture.

 

I would also say this problem has been getting steadily worse over around 2 years of occasional use.

 

Really happy with response. Great forum

[rollingreenhills]

Well thanks for your replies again.

 

I suspected an air leak, and have gradually been taking apart the saw.

 

Eventually I found a ruptured impulse seal which I think may be the culprit. Genuine part only though £10 for a small tube the size of an earser that you find on the end of a pencil!

 

I have written up my finding here is any is interested.