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 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 holes 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!

 

[Jasent]

How’s the spark look? Blue or orange?

 

[tomalophicon]

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 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 holes 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!

Have you checked spark? How about electrical connections and coil air gap? You mention a new plug but maybe spark isn't there or inadequate?

Flywheel timing key?

 

[atpchas]

How’s the spark look? Blue or orange?

Good bright blue spark. Easily jumps the 1/4" gap in my tester.

 

[atpchas]

Have you checked spark? How about electrical connections and coil air gap? You mention a new plug but maybe spark isn't there or inadequate?

Flywheel timing key?

Plenty of spark. Electrical connections are sound. Relatively new saw, wire coatings are still very flexible, no age cracks in insulation. Coil gap is usual business card and key is in its slot.

 

[tomalophicon]

Internal muffler blockage?

 

[atpchas]

Internal muffler blockage?

No blockage, screen is clean. In my experience blocked exhaust tends to cause a machine to not reach full rpms. I've got the reverse problem.
But thanks for the suggestion - at this point I'll look at just about anything.

 

[Jasent]

I’m working on a husky 41 with bad carb. It’s sucking air threw the throttle shaft. Took me forever to find the leak!!!! Would not idle with out choke

 

[GeorgiaVol]

Bad gas?

 

[cuinrearview]

I had a 450 smear the FW key and jump time.

 

[atpchas]

I’m working on a husky 41 with bad carb. It’s sucking air threw the throttle shaft. Took me forever to find the leak!!!! Would not idle with out choke

Same saw behavior with multiple carbs tends to rule that out.

Bad gas?

No, less than 2 weeks old and all my other machines run it happily.

I had a 450 smear the FW key and jump time.

That was a problem (self-inflicted, don't ask) until I replaced the FW.

 

[GeorgiaVol]

Fuel lines attached backwards? yep I did that.
Pinched fuel line?
Something in the fuel line?

 

[atpchas]

Fuel lines attached backwards? yep I did that.
Pinched fuel line?
Something in the fuel line?

Good suggestions but the fuel lines on this saw are pretty hard to screw up and easy to monitor for pinches. Nothing blocking lines when I blow through them.

 

[GeorgiaVol]

I have one that is similar. Won't settle the idle. Jumps around a lot. Originally, I found out the wrong needle valve was put in, but even after that it wasn't right. I just plan on replacing the bearing seals. They are old anyway. I'll see if that helps.

 

[GeorgiaVol]

Those are those strato Zama carbs right?
Those are real finicky in the saws I have tried to fix. I don't like those at all.

 

[atpchas]

Those are those strato Zama carbs right?
Those are real finicky in the saws I have tried to fix. I don't like those at all.

Yes, the C1M-EL37B. Problem is I can't get the rpms to a point that I can even begin to tune. The saw wants to race at near cutting speed or die as soon as the revs drop to what I'd guess is 4-5K or so.

 

[J D]

What base adjustment are you starting with? I think they should be set at 2 or 3 turns out not the usual 1 to 1½

 

[atpchas]

What base adjustment are you starting with? I think they should be set at 2 or 3 turns out not the usual 1 to 1½

The shop manual I have says 2 turns each on H & L. I've tried everything from 1 to 3.

 

[atpchas]

It's been more than a year since I posted about this and got many useful suggestions as to what might be the source of the problem. Since the owner made no effort to retrieve the saw, I let it sit. I recently took another go at getting the saw to run right and finally discovered the source of the problem. I might have found the issue earlier if (a) I knew more about strato charge engines and (b) that someone fiddles with the carb/strato parts before it came to me.

The picture shows how the butterfly for the strato air is supposed to look. My saw had the little circular hole fully open and the butterfly itself cocked so that significant air went through even at idle. Actually, so much air got through that stable idle was unobtainable. Had I known better, I might have seen that for the gigantic air leak it was. In my ignorance I assumed that was the way it should be. All I can figure is someone "modified" the butterfly because it could not have possibly migrated to that setting on its own.



As soon as I repositioned the plate so it closed off air as completely as possible, the saw started behaving properly and was easily dialed in for stable idle and good throttle response. I'll try to put it in some wood tomorrow just to make sure the high speed setting is healthy.

Thanks again to all who made suggestions.