Husqvarna 445 won't rev up

[Nutball]

I'm not in to working on these 4xx series saws, or chasing down strange problems anyway. I'm not going to rebuild the carb. I was told this saw worked well recently, but suddenly had the issue.

It starts and idles, stalls occasionally. It will fast idle a little faster than idle, but not much more and it sounds rich when fast idling. I was able to tune it to run on full throttle (I turned it .5 turn rich). The engine responds to tuning, but not by much. I can close the needles, and open them too much.

Full throttle runs slightly slower than it does barely above idle (where it is fastest, but barely moves the chain). I'm assuming some glitch in the ignition is limiting its max rpm to idle. The faster it goes, the more strokes the ignition misses causing the rough 4 stroking sound.

That's my assumption, what's yours? I'm ok with trying a $12 ignition, but otherwise it's going on ebay.

 

[Nutball]

Note the smoke is because I put lots of benol in the carb to make sure low compression wasn't causing the issue, but no change.

 

[Simondo]

I'm not in to working on these 4xx series saws, or chasing down strange problems anyway. I'm not going to rebuild the carb. I was told this saw worked well recently, but suddenly had the issue.

It starts and idles, stalls occasionally. It will fast idle a little faster than idle, but not much more and it sounds rich when fast idling. I was able to tune it to run on full throttle (I turned it .5 turn rich). The engine responds to tuning, but not by much. I can close the needles, and open them too much.

Full throttle runs slightly slower than it does barely above idle (where it is fastest, but barely moves the chain). I'm assuming some glitch in the ignition is limiting its max rpm to idle. The faster it goes, the more strokes the ignition misses causing the rough 4 stroking sound.

That's my assumption, what's yours? I'm ok with trying a $12 ignition, but otherwise it's going on ebay.

Ignition limiter coil issue sound about right to me and if you can get coil for $12.00 to eliminate .......

 

[Wood Doctor]

This reminds me of a problem I just solved with a Stihl gas leaf blower. The exhaust port screen on the muffler was blocked with caked on, burned up gunk so bad that is was solid black. I removed the screen, cleaned it all up with solvents (gas, acetone, etc,) so that I could see through the screen again, put it back on and the engine ran perfectly. It's possible your exhaust port is blocked the same way. It's worth a look, anyway.

 

[Nutball]

That was the first thing I checked

 

[beaglebriar]

Coils shot.

 

[Nutball]

Coils shot.

Not yet, I haven't been to the range

 

[Wood Doctor]

That was the first thing I checked.

Are you sure? I did not see that mentioned in your earlier posts, #1 or #2. Can you show a Pic of the muffler's spark screen?

 

[Nutball]

I'm sure, It was so the first thing I checked, that I was long over it by the time I posted, so I forgot to mention it. I had just thrown away the spark screen in a 193t before the guy hand's me the 445 to fix.

 

[Stump Shot]

Sure sounds like the ignition is giving it the fits.

 

[Stump Shot]

... either that or it's having an allergic reaction to the Castor bean oil.

 

[Nutball]

The new ignition spun it up to about 1/4 throttle, chain speed is way faster than before, but still can't get full rpm or even close to it. I tried leaning the high speed thinking it was just rich, but no rpm increase, just an audible leaning sound. The flywheel appears to be positioned correctly: magnet reaching the coil near TDC. I don't know exactly how they are to be positioned since I assume the coil waits nearly a full turn after the magnet goes by before sparking. I haven't checked the key though.

120psi warm

 

[Spike60]

Coils shot.

Yup, definitely the coil.

573 935 702 About $23

 

[Nutball]

I find it strange that the aftermarket coil spun a little faster, but still not near where it should. I'm doubting the coil being the problem.

 

[Terry Syd]

I'm interested in that aftermarket coil. The stock coil has a rev limiter at 13,000. I've modded my 450 enough that it likes to cut between 12,000 and 12,500. The rev limiter works as a 'dull chain indicator'.

Gawd, if I had access to an unlimited coil, I might be stupid enough to have a pop-up piston made for it (the cranking pressure is around 145 psi) Then I could tune it for cutting at around 13,000-13,500. I don't really need that extra cutting speed, but most of the guys on the forum would understand why I did it...

 

[Spike60]

Really? Went with an aftermarket coil when the OEM only lists for $22.99?

Also want to point out that there is a difference between the 445/450 and the newer saws with the "II" designation. (they don't say "mark II" like the new 550's, just 450II or whatever. So it brings up the question: is the saw in the OP a 445 or 445 II?

Those new "II" saws, without the decos, have a different coil, that costs $72 BTW. The deal is the new coils are made to fire at a lower RPM when starting. Something like 700 rpm vs 1400-1500 for the original coil. That and a spring assist starter are way better than a deco cause there's no compression drop when starting. (This is also why the new 545/550 have no deco.) And there's never a concern about a leaking deco either.

In addition to different coils, the 2 generations of these saws also use different flywheels. I'm not sure if you can mix and match them or not. Don't know that I've tried it yet. One thing I do know is that the new coils hardly ever fail. Not uncommon for the old ones to go.

 

[Nutball]

The primer bulb won't fill with gas

 

[Nutball]

I put the old ignition back on and fired it up again to make sure all works like it has before trying to sell it, and it revved up fine, cut well.