Help with 288xp running problems

[bnmc98]

I have a 288xp supposedly rebuilt recently. was running fine a while ago, then developed a problem of not staying in tune. I thought the screws were backing out as I had to reset them and it would load up and run pig rich after working with it a little bit. so I replaced the needles and springs. would last about 15 minutes before it would run rich again. so I ordered a brand new tillotson carb for it. needless to say that wasn't the problem obviously.

Saw will run with high screw shut all the way and not run lean. will also decrease in idle and almost die if I roll it sprocket side up, will not tune right with low screw either. Cant seem to figure this one out as I thought air leaks made them run lean.

I recently had the oil pump out of it, the seal was reseated on that side (sprocket) and everything looked fine and went back together the way it should, I was watching the tech do it and he's pretty reputable around here.

Thoughts????

 

[bnmc98]

nobody wants to take a stab at it. maybe I got a bum carb but that wouldn't explain the problems with the previous one.

 

[RandyMac]

the stihl guys are off sucking their thumbs.

15 minutes run time is long enough to heat up the fuel in the tank, perhaps there is too much pressure in the fuel tank, check the vent.

 

[lfnh]

I have a 288xp supposedly rebuilt recently. was running fine a while ago, then developed a problem of not staying in tune. I thought the screws were backing out as I had to reset them and it would load up and run pig rich after working with it a little bit. so I replaced the needles and springs. would last about 15 minutes before it would run rich again. so I ordered a brand new tillotson carb for it. needless to say that wasn't the problem obviously.

Saw will run with high screw shut all the way and not run lean. will also decrease in idle and almost die if I roll it sprocket side up, will not tune right with low screw either. Cant seem to figure this one out as I thought air leaks made them run lean.

I recently had the oil pump out of it, the seal was reseated on that side (sprocket) and everything looked fine and went back together the way it should, I was watching the tech do it and he's pretty reputable around here.

Thoughts????

that saw has two seals in oiler body. crank seal should not be reused, and only oem (imo) and outer should be too al though that one isn;t under rotation, but smart and cheaper in end.
how long did tech run vac test for and was crank turned during test.
new carb still should have p-test done
needle and float tab should be checked to make sure that section not letting to much feul by.
been a couple of threads on 288 carb problems lately, that'd be worth checking.

 

[bnmc98]

thanks I will give them a shot including the vent

 

[Eccentric]

Another vote for replacing the crank seal on the PTO side. Also replace the o-ring on the oil pump body where it fits into the crankcase. Use the actual Husky part. If you haven't replaced the flywheel side seal then I suggest you replace that while you're at it. Start with a clean slate.

Since you installed a brand new carb, the problem should lie here rather than in the carburetor. As far as your old carb is concerned:

The 'super rich' issues sound like the governor valve in the carburetor is malfunctioning. Best thing to do with it is to block off the valve. You'll have to remove the carb for this. Use a good, tight fitting screwdriver (I use a hollow ground screwdriver for this) and unscrew the brass governor valve assembly. Cut a .250" disc from a beer/soda can and drop the disc into the hole in the carb body. Put some sealer on the threaded portion (and only the threaded portion) of the governor valve and screw it back in tight. Set your needles at one turn out each and see if she'll tune right now.

 

[bnmc98]

well seeing as the new carburetor did the same thing as the old, I think I will just leave the old carb the way it is. Using the KISS philosophy I first checked the vent before I dove into more time consuming areas.

BTW wouldn't bad seals make the engine race lean instead of richen up?

I cant blow air through the vent, Looks like there is a hard plastic disc in the vent housing as well as there was one used as a plug over the vent on the tank. Is this some special porous material or what. Looks like is was foam at one time but hardened over age. anyways have not dove into a vent before but I cant see how pressure could get through that. correct me if I am wrong. I have one from a old 181 that I cant blow through either, am I missing something or is it clogged?

 

[Eccentric]

You won't be able to blow through the vent. It's a check valve. Primary function is to let air in as the fuel is drawn from the tank..................without letting gas out. Some tank vents also release excess tank pressure. I can't remember if the Husqvarna vents do this or not.

Saws don't always race/rev up when they have leaking crank seals (or any other air leak). The changing tune with the tilt of the saw is a classic sign of leaking crank seals (although it also doesn't always happen with leaking seals).