576xp does not run correctly

[mbrick]

Been trying to figure out this saw for a while now. Bought this Husqvarna 576xp not running earlier this year. Pulled cyl and had very minor scoring, but piston mic'd small and ring gap was a bit large so I replaced them both. Flywheel side crank seal leaked a little so I replaced that.

It now starts (barely) but does not idle and does not rev up above 10k at WOT.

Looks to me like it has a little excess fuel spitting back out the carb.
It also seems to get hot, fairly quick. After a few seconds of revving up the exhaust and cyl are too hot to touch. I usually run with the cover on, this was just for a quick video.

Put on new OEM parts: P&C, carb rebuild kit, fuel line, pulse line, clutch cover.
Did not run right so I bought a new OEM carb and ignition coil.
Still did not run right so I bought another new OEM carb, same symptoms.

Compression is 148 psi cold, actually the same as before I took it apart. Holds 8psi pressure and 15 in Hg vacuum for 5 minutes with no drop. Re-adjusted coil gap to spec.

Tried various metering lever adjustments on carb #2. Carb does not respond to H needle all the way in and out to 3 turns. Does not idle unless I have the idle screw WAY in (at end of taper) and even then it tends to hunt around a bit. Took the carb diaphragm off and held the needle down while pulling it over and it flows a lot of fuel. It actually seems like it is using way too much fuel, just a sense from how little I've ran it and already being at about 1/2 tank.

Just ran it with the exhaust off to confirm the minor denting in the front was not restricting it. No difference, other than being louder.

I'm out of ideas on this one and would appreciate any suggestions. Way too much $ into it already.

Here is a video of how it sounds with the exhaust off:
https://photos.app.goo.gl/gK3jnGQVvpxZy3JUA

 

[lostone]

After the saw has sat for a bit does it run ok for a min or so then start doing this?

Is what I am getting at is have you checked the fuel tank vent? maybe drawing a vacuum and starving the saw. I have no idea myself since I am not familiar with this saw but if it's getting a fuel delivery issue because it cannot get enough fuel it would run lean (hot) as well as since the fuel is being metered by the lack of fuel to the carb then adjusting the carb wouldn't help.

Edit: just read where you say it's getting to much fuel.

 

[cus_deluxe]

maybe somehow the flywheel has slipped and the timing is way advanced?

 

[lostone]

maybe somehow the flywheel has slipped and the timing is way advanced?

He did pull the flywheel to replace seal so maybe didn't get it tightened back up???

 

[Brent Nowell]

Main nozzle check valve good?

 

[cus_deluxe]

He did pull the flywheel to replace seal so maybe didn't get it tightened back up???

kind of what i thought. timing WAY advanced will run way hot real quick, and not make rpms. seems like hes covered the usual stuff.

 

[backhoelover]

Tb

 

[mbrick]

Lostone, it doesn't run differently if I crack the tank cap or wait after sitting a while. It's immediately like this. I did check the tank with the mityvac on the fuel line and it was venting.

Brent, I did check the main nozzle check valve on the first carb. Punched it out and checked it with the mityvac and it was ok (one directional) if that's what you mean. I did not touch the 2nd and 3rd carbs since they are new OEM. That is what I though the issue was going to be... way over fueling.

cus_deluxe, the flywheel has the cast-in key and I lined it back up when reinstalling and tightened it. I also visually checked based on prior advice that the front of the magnet passes the coil pickup at TDC (can't remember exact instructions but it looked correct).
Does it need to be off by a small amount I might not see by eye, or a lot? I should pull the fly wheel again and just take a look to make sure the key is OK. I can do that.

backhoelover, thanks for the coil info. The new coil I bought was 510115701 so that looks correct based on your info. I did see it covers 372 through 576 now. It is different P/N than the coil that originally came on the saw but the rpm limit written on there is the same. Both run the same.

 

[backhoelover]

Have you check to see if butterflys are opening all the way. Also check plug I’ve had a few new plug been bad

 

[mbrick]

Yes, I did check and the linkage opens it all the way.

The plug has spark, what do you mean by checking it? The ones you had bad, did they exhibit similar symptoms?

 

[Huskybill]

Always check the sparkplug first, then the fuel supply. Then compression next if no improvement.

My 575 just broke my stones but a quick carb adjustment fixed it. From new it has ten cords of wood on it. It’s more backup for my 385 XP now.

With the older huskys I had there was summer and winter adjustments on the low screw the high screw was always ok. I wonder if these newer saws need weather related adjustments too?

 

[superwd6]

Yes, I did check and the linkage opens it all the way.

The plug has spark, what do you mean by checking it? The ones you had bad, did they exhibit similar symptoms?

Piston in backwards? Was this a saw somebody else played with before you got it? Another guy had 576 bottom end the previous person put 575 cylinder on and didn’t work properly.


Sent from my iPad using Tapatalk

 

[mbrick]

I think the piston is in correct, good idea to check though. Here is the new piston after I took the cyl back off to look it over and make sure I didn't see anything obvious causing it to run poorly.

I do not believe this saw was played with, it came from a arborist company and was very dirty especially in the stator area around the leaky crank seal and not maintained from my best judgement. I could be wrong though but there were not marks on fasteners like flywheel nut or ignition coil of them having been removed previously and exh screws were very tight. It did have the adjuster screw boot for the earlier carb style but came with the newer carb.

They are 576 cases based on the tag and port shapes at the front side that match the old cylinder ports and a new 576 cyl. I did at one point think the original piston may have been a 575 but after comparing to the new parts it was correct.

 

[backhoelover]

Try a new plug and can u get a pic of plug that has been running In it?

 

[backhoelover]

What year is saw and what carb did u buy?

 

[mbrick]

Here is a photo of the first plug I tried (left, Bosch WS7F) and right (NGK BPMR7A). I know there is a missing thread on nut on one, I took it off to make sure the threads were ok and dropped it. Did not run it like that.

Saw is a 2011, bought carb 580735801. Zama EL50. It's on the IPL and parts fiche.

 

[MacAttack]

Here is a photo of the first plug I tried (left, Bosch WS7F) and right (NGK BPMR7A). I know there is a missing thread on nut on one, I took it off to make sure the threads were ok and dropped it. Did not run it like that.

Saw is a 2011, bought carb 580735801. Zama EL50. It's on the IPL and parts fiche.

They don't look to me like you have a lean condition, if anything they look a bit rich.

You mentioned the high speed circuit adjustment has no effect on how the saw runs? That's very strange, like it's getting too much fuel some other way...

 

[mbrick]

I am out of town for Thanksgiving, but can record another video when I am back while adjusting the H screw. I'll also remove the stator and take a look to make sure it is ok.

I held it WOT and turned the H screw from closed to 3 turns and it did not increase in rpm. Checking with the Oppama it is hovering around 10k rpm.
I agree it seems like it must be getting too much fuel but I'm not sure why?

 

[Ozhoo]

Seems to me that the strato valve isn't opening... if it is, then not opening all the way

 

[mbrick]

maybe somehow the flywheel has slipped and the timing is way advanced?

So I think you might be right...

I removed the flywheel and the integrated aluminum woodruff key is sheared!!!
I have a rough idea of the position before removing based on where I placed the magnet opposite the coil (should have marked it exactly). Based on where I think it was visually, it was either lined up or rotated clockwise by about 20-30 degrees. Clockwise means timing is retarded though?

How much would it need to be off to run as crappy as it was? Maybe this would explain why it also seems to run hotter than it should?

Do I need to replace the flywheel, or can it be lined up/timed and then tightened and not expected to slip while running? I imagine the modders adjusting timing are doing it without a key so it can be turned?

What could cause it to break like this? Does the face need to be lubricated so the nut does not try to rotate it during tightening? The key was in-tact before reassembly.

Ozhoo, I checked and the strato valve is opening all the way. Here is a photo.