Husqvarna 450 x-torq, help needed

[atpchas]

I'm working on a Husky 450 x-torq for a buddy's buddy, so the history is less than ideal. Basic statement of problem I'm seeing: saw starts (reluctantly) but will not run at anything approaching an idle. Things I've done/checked:
1. Tried several different carbs, no appreciable change.
2. New fuel lines and filter - no change,
3. P/V tested (twice) - tight as a drum.
4. Fresh spark plug
5. Compression is about 140 - not great but certainly should be adequate.
6. Rubber manifold between carb and cylinder is sound, no tears or rubber rot.
7. MityVac plugged into impulse tube shows pressure changes when engine is pulled over.
8. Tried all sorts of variations on needles from approx 1 turn out to 3. Shop manual says start at 2 turns on H & L.
9. No scoring evident through muff port or carb ports.

Thanks for any other avenues to pursue before I completely give up on this saw.

P.S. The engineer/designer who thought it would be fun for the carb needle access hole to hide behind the rope handle should be sentenced to eternity trying to make adjustments on such a saw when it requires one hand on throttle to keep it running. AAARRRGH!


Moved to the Chainsaw forum where I meant to post it initially. Senior moments, gotta love 'em.

 

[ndlawrence]

Have you checked to coil-to-flywheel gap? What about the coil itself?

 

[atpchas]

Have you checked to coil-to-flywheel gap? What about the coil itself?

Checked the gap, no problem there. As to checking the coil, what test(s) are you suggesting?

 

[ndlawrence]

Checked the gap, no problem there. As to checking the coil, what test(s) are you suggesting?

Someone with a shop manual for the 450 can chime in with the resistance specs.

 

[atpchas]

Someone with a shop manual for the 450 can chime in with the resistance specs.

Finding resistance specs is annoyingly difficult. The shop manual I have only suggests checking that plug makes a spark (pull plug, lay on cylinder, pull cord, observe), no resistance test mentioned.

 

[ndlawrence]

Finding resistance specs is annoyingly difficult. The shop manual I have only suggests checking that plug makes a spark (pull plug, lay on cylinder, pull cord, observe), no resistance test mentioned.

Try another coil then.

 

[atpchas]

Try another coil then.

I'm getting ready to do just that. There's not much else left to check.

 

[cscltd]

435-450 modules sometimes failed and still showed spark.

 

[smokey7]

Been seeing a quite a few of the limited coils and some on coils with the built in retard/advance. They have issues when making the switch. Try another coil and make sure strato/choke butterfly's work right.

 

[atpchas]

Try another coil then.

435-450 modules sometimes failed and still showed spark.

Been seeing a quite a few of the limited coils and some on coils with the built in retard/advance. They have issues when making the switch. Try another coil and make sure strato/choke butterfly's work right.

Just ordered a new Husqvarna coil. My ohm meter shows the primary as an open circuit. Hope this cures what ails it. Will update when the new coil arrives.

 

[smokey7]

When the internal circuit for advance/retard fails they still spark and test good but have issues running

 

[atpchas]

When the internal circuit for advance/retard fails they still spark and test good but have issues running

That describes this saw, for sure. It does run and the spark looks super strong but it can't sustain low rpms.