Alright, So What Happened?

Bryce Frazier · Feb 26, 2016

Was sawing all day. Started out running my Husqvarna 288XP. Ran the thing most of the day, probably cut 3 or 4 cords of wood with it. All of a sudden, it started not wanting to idle, ran good, and had good power, but was high idling, just, running way too fast on what should have been "idle". Decided it was best just to dismiss it for the day, and got out one of my other saws to finish up.

Get home tonight, and fire it up, same thing. Starts / runs great, but idling really high?? Shut the saw off, and made a carb adjustment, won't run now, and I noticed a knocking sound (fairly loud) when I am pulling on the rope?? Something must have failed internally, but, considering the events, I really don't know WHAT that something might be?? Nothing feels different when I am pulling it through, even very slowly? Still has good compression too?

I completely rebuilt the saw, it has new everything inside it. Meteor piston.

Thoughts?

47fivewindow · Feb 26, 2016

Flywheel key dented, changing timing?

roy prins · Feb 26, 2016

sucking air somewhere -- changing the fuel to air ratio

johnlobb · Feb 26, 2016

I agree with Roy. Could be a crank seal or a hole or crack in a fuel line..

Ozlander · Feb 26, 2016

Bryce Frazier · Feb 26, 2016

Ya, I had that though.... Took the air cleaner off first thing just to see if that made a difference, but it didn't. If it was getting air somewhere else though, I suppose it would be running lean, which WOULD explain the higher idle right?

Not sure what that sound is though??

UAFitter · Feb 26, 2016

My money is on a bad crank seal, and I'd bet the clunk is the bad bearing that took out the seal.

Bryce Frazier · Feb 26, 2016

Thats another solid possibility.....

No offense, but I reallllly hope you are wrong! :/

ss55 · Feb 26, 2016

That does sounds like a lean fuel mixture at idle. If it improves with a full tank of fuel or by tilting the saw to submerge most of the fuel line, look for a cracked fuel line inside the tank. Other possible causes could be: partially clogged idle circuit in the carb; leaking intake gasket, crankcase gasket or seal.

John - OH · Feb 26, 2016

I'm betting bad crank seal. I'm also guessing the piston got hot, started to melt and the rings stuck, now catching on the port as the piston goes up and down causing the clunking. Lets hope not, but I guess you will find out when you open it up. Let us know what you find.

Russ from MN · Feb 26, 2016

No school today?

notjustair · Feb 26, 2016

Sounds like one I had. Piston started to melt and scored the devil out of the cylinder. It still felt like it had pretty good compression but it is in the parts box now.

Adirondack case guy · Feb 26, 2016

I think you nailed it.
Loren

UncleTom · Feb 27, 2016

High idle means leaned out to me. Also clunking could be scored piston. Give us some follow up when you find it.

GVSII · Feb 27, 2016

(quoted from post at 18:25:34 02/26/16) My money is on a bad crank seal, and I'd bet the clunk is the bad bearing that took out the seal.

That'd be my guess.

JD Seller · Feb 27, 2016

I will second or third the fellows that state a lean burn issue that over heated the piston. The temperatures are warmer than normal this year. In warm weather you can lean out a two cycle too much and it will not get enough oil to lube and will also run hot. I hope not for your pocket book.

What I have found helps in warm or hit running of two cycles is running them richer than you normally would. When you adjust the carb. richen it up to where the motor is real doggy and then just lean it down a little to where it runs well. DO not lean it down to MX engine RPM like you can in the cooler months. I also run a low ration of oil in the gas in warmer weather. I can afford spark plugs easier than pistons/rings/cylinders/jugs. I am actually running 16-1 with a good low ash oil. I know most of the stuff is calling for 32 or even 50 to one mixes but I have had few engines ever fail because of too much lubrication.

T in NE · Feb 27, 2016

Running higher octane gas helps too. Its less apt to pre-detonate. Pre-detonation effectively advances your timing and can lead to melted pistons.

Alright, So What Happened?

Bryce Frazier

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47fivewindow

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roy prins

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johnlobb

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Ozlander

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Bryce Frazier

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UAFitter

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Bryce Frazier

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ss55

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John - OH

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Russ from MN

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notjustair

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Adirondack case guy

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UncleTom

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GVSII

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JD Seller

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T in NE

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