Need Husqvarna 576 help

[CoreyB]

Have a long story but need help. Have a 576 that came into the shop last week low on power and sounds like it is missing. Have a new mechanic that is having trouble diagnosing the issue. It has good spark. Starts easy but just never quiet right. Any help would be awesome. @Spike60 @Miller Mod Saws @Mastermind
OR please lead me to someone who may be able to help.
Thank you guys

 

[huskyboy]

Is it an autotune?

 

[Duce]

Do a vacuum test. 576 and 575 like to eat clutch side bearings from time to time. If you have to replace bearing, make sure to use a sleeve retainer. Bearing and seal are all in one.

 

[Onan18]

Is it an autotune?

This, also out of curiosity did you try a new spark plug, sometimes it is the simple things. I had a run of them with leaking decomp valves, have you pulled the muffler and inspected, pressure/vac test?

Joe

 

[CoreyB]

Is it an autotune?

This, also out of curiosity did you try a new spark plug, sometimes it is the simple things. I had a run of them with leaking decomp valves, have you pulled the muffler and inspected, pressure/vac test?

Joe

Yes it is an Auto tune and we did replace the spark plug and fuel filter. Dumped the gas put ours in. Have not done a pressure vac test. Mechanic says no scoring and compression is 120.

 

[Duce]

Compression is low, plug decomp valve and re-check. Does he want to trade it in, or sell it?

 

[Mastermind]

Check coil air gap, flywheel key, carb, fuel line, etc....

 

[Onan18]

Check coil air gap, flywheel key, carb, fuel line, etc....

Especially this, pull it out of the tank, seen them crack at the tank more times than I can count.

 

[backhoelover]

Didn't hey have a problem with cylinder plateing at one time?

 

[backhoelover]

Also Is everything up to date?

 

[CoreyB]

Also Is everything up to date?

This is the older style AT so I don't think it can be updated or hooked up to the diagnostic tool

 

[huskyboy]

Compression should be around 140-150 at least. Might need carb kit and set of rings in very least is my guess

 

[backhoelover]

oh you can reset them

 

[Outback]

Im gonna ignore the compression test. Don't forget the ever lovable side fin/plug wire melt through...... I've replaced a coil before I found a little melted spot on the plug wire once. I've never messed with a 576, so if it doesn't route the wire that way forgive me.

 

[Spike60]

Gotta get out the mighty vac and do the pressure test on these things. Air leaks are not all that common, but can occur in several places. Could be simple case of a bad deco. The first generation AT is great at compensating for air leaks as it would "default rich" and dump fuel into the saw. This actually saves a lots of saws from toasting themselves. Just replaced a torn intake boot on one that would surely have fried if it wasn't AT. But this can also send a tech off in the wrong direction bacause the typical air leak symptoms are masked.

Another thing to keep in mind about the 576 AT is that it MUST have the gray coil to run properly. Put any of the blue or black coils, (or aftermarket coil), in there and it will run totally screwed up.

 

[Stump Shot]

Have a long story but need help. Have a 576 that came into the shop last week low on power and sounds like it is missing. Have a new mechanic that is having trouble diagnosing the issue. It has good spark. Starts easy but just never quiet right. Any help would be awesome. @Spike60 @Miller Mod Saws @Mastermind
OR please lead me to someone who may be able to help.
Thank you guys

When you say good spark, will it jump say a 5mm air gap and be a bright blue color, not white or pink? If not the coil could be giving out what I like to call a ghost spark, not really enough to run on under compression. Which you don't seem to have a lot of which may lead the saw to run just a bit.(Possibly) if no air leaks are found check the muffler screen, then pull the muffler and check for collapsed/broken ring/s or even a loosened ring pin. Of course all the above advice should be headed as well. Hard to diagnose stuff through this key board, but if your mechanic stays the course and starts crossing things off the list it will eventually point him in the right direction.

 

[Adirondackstihl]

Didn't some of them have base gasket issues or was that the 575?

 

[huskyboy]

I know the 575 spun bearings in the case I believe but that was fixed with the 576

 

[CoreyB]

How long of a spark should it get in a spark gap test?

 

[Stump Shot]

How long of a spark should it get in a spark gap test?

Opinions may differ slightly here, as it really depends on the output of the coil, but as a general rule I follow any coil should jump a 5 millimeter air gap out in the open.(Husqvarna does offer a spark checking tool for this purpose and is a good one) This mimics the spark under compression. If it won't jump, is puny/skinny/weak/light in color or the wrong color your coil is suspect. If it has a good bright blue spark that snaps across the gap, you should have a good coil. Then move on to one of the other things a motor needs to run, fuel compression and exhaust. Some of these newer saws are giving newer problems, so keep an open mind and keep digging. Also please let us know what the outcome was after it is found. SS