Husqvarna 55Rancher Won't Rev Up as Before

[sonnyboy53]

I've had a Husky 55Rancher for a little over a year and it's been a great saw.  A month or two ago, it would not rev up as it once did and it will kill more often than not.  I worked on saws for years and so I thought I had seen it all but this one's got me stumped. The saw starts fine cold and restarts OK when warm.  It idles & will get up to about half speed but that's it.   This is what I've tried so far:  cleaned the carb (Walbro not Zama) & installed new kit (no difference in operation), checked compression (135psi), checked crankcase for vacuum & pressure (no leaks), checked fuel tank vent (fine, not blocked), checked impulse grommet (seemed OK but didn't replace), checked muffler for carbon build up (found none).  I have not bought a new ignition module but am leaning in that direction as that's about all I can think of. 
Before doing that, can any of you think of anything I've over looked or that I should go back to & recheck?

[mike_belben]

Youve tuned carb to no avail?


Gotta pressure test it.  

Build a blank off plate for the muffler with a piece of sheetmetal and a rubber inner tube cut into a gasket.  Use your compression tester adapter to rig up a way to put air into plug hole.  Dont forget to pull schrader out.  The intake is a pain to block off if its the round boot style.  Spray soapy water while you pump it up to look for leaks around crank seals and intake boot, base area etc.  Thats a clamshell right?  


Otherwise id say be sure the float tab is adjusted right.  Tanks vented, fuel pickup filter isnt full of algae and is opening. Lines not turning to dust etc

[Tin Horse]

My Dolmar 5105 did the exact same thing. Less than 2 years old. Took it back to my dealer and he said it was the coil. $200.00 plus and it's ok now. Never had a coil fail. He says it happens a lot now.

[sonnyboy53]

Mike:
As I said, I have done both a pressure & vacuum test on the crankcase, checked the fuel tank vent and I didn't mention it in the original post but the fuel filter & lines have been replaced.  It's not a clamshell design-the jug sits in the crankcase and the bearings & seals fit into each half of the crankcase.  Thanks anyhow

[dougand3]

You've checked most all items. Could be coil. May be carb. You try a new carb. Clones of WT-170 are readily available.

[wild262]

              I would check or swap coil if I were you, and make sure no wires are shorting out on the case or cyl. somewhere.  Maybe flywheel key.

[sonnyboy53]

With just about everyone mentioning the coil, I think I'm going to look at that.  The Walbro WT-170 is a replacement as the saw had the original Zama on it when I got it.  I've had better luck with Walbros.
Thanks for the help & I'll keep you posted.