372 XP goes lean when hot

[RedFir Down]

I scratching my head guys...
I have a 2001 (pre x-torq) 372. After cutting with it for roughly 10-15 minutes the saw goes lean.

I've pressure/vac tested and it holds 10 psi for 5 minutes with zero loss so the case is tight.
I changed the fuel line and filter at the start of the year (probably 25 tanks of fuel). OEM fuel line, Walbro filter.
The carb holds pressure. I opened up the carb and everything looks normal.
I also made sure there wasn't a small hole in the fuel line.
The tank vent is venting properly.

Has anyone had crank seals fail when the saw is a operating temp?

Thanks for the help fellas.

 

[Stevetheboatguy]

Try a low pressure test also. 2psi.

Sometimes when you apply a higer pressure it will cause a seal to well um..... Seal.

Steven

 

[Crocky28]

Try moving the intake boot when it’s under pressure. I’ve had one test fine and the boot was leaking but I had to move it about to get it to leak. The boots go and the flanges go. Either that or the clutch side crank seal and o ring. They always go. I also change the the metal sleeve while I’m in there as they wear slightly.


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[huskihl]

The intake manifold bracket is probably warping from over tightening when it gets warm. Farmertec makes an aluminum replacement that is actually a better part than the OEM

 

[John235]

Sounds awful funny reading farmertec make a better then oem part. But I 100% agree. I have one on mine.

 

[huskihl]

Sounds awful funny reading farmertec make a better then oem part. But I 100% agree. I have one on mine.

Same here. I said nope for 2 years. Finally picked up a few since they work on both 372 and 7900’s. I clean up some casting flash so it doesn’t wear on the boot, but so far other than that they’re spot on

 

[Duane(Pa)]

Great info Kevin!

 

[RedFir Down]

Try a low pressure test also. 2psi.

Sometimes when you apply a higer pressure it will cause a seal to well um..... Seal.

Steven

Good idea! I put about 4 to 5 psi and let it hang out for a minute or 2 with no change.

Try moving the intake boot when it’s under pressure. I’ve had one test fine and the boot was leaking but I had to move it about to get it to leak. The boots go and the flanges go. Either that or the clutch side crank seal and o ring. They always go. I also change the the metal sleeve while I’m in there as they wear slightly.


Sent from my iPhone using Tapatalk

I like your thinking. I gave that a shot as well with no change. I'll dive in deeper.

The intake manifold bracket is probably warping from over tightening when it gets warm. Farmertec makes an aluminum replacement that is actually a better part than the OEM

Interesting, thanks Kevin. That was the second most likely area I was thinking it might leak. Kind of a poor design.

 

[huskihl]

Good idea! I put about 4 to 5 psi and let it hang out for a minute or 2 with no change.


I like your thinking. I gave that a shot as well with no change. I'll dive in deeper.


Interesting, thanks Kevin. That was the second most likely area I was thinking it might leak. Kind of a poor design.

Trickle some carb cleaner around that area when it’s acting up

 

[mrxlh]

Trickle some carb cleaner around that area when it’s acting up

Brake clean works just as good…

 

[huskihl]

Brake clean works just as good…

Yep. Just something flammable

 

[Mastermind]

I like to do vacuum before pressure. As Steve said, pressure can actually seal stuff up.

 

[Stump Shot]

Has anyone had crank seals fail when the saw is a operating temp?

Yes, I've had a couple, my old 272xp used to do that when I was milling with it, I would tune it back to normal with the leak until I corrected the problem with new seals.
I have an old Homelite that does this as well, I don't care enough about it to fix it so I just make a few cuts to make some noise and shut it back down.
These are usually the ones that with the top end removed the crank can be rolled with near zero resistance. So they're basically worn down to near the size of the crankshaft and expand when warmed, then the leak, contract back when cooled, back to sealed.
To warn though, this isn't the only thing that will mimic this condition, a top end could be having a gasket failure, as mentioned the manifold could be having a problem, crankcase having a gasket sealing issue and so on.
So poke around pretty good and also as mentioned a can of either can help find it when it is warm and leaking.
Good luck with your repair

 

[kneedeepinsaws]

I scratching my head guys...
I have a 2001 (pre x-torq) 372. After cutting with it for roughly 10-15 minutes the saw goes lean.

I've pressure/vac tested and it holds 10 psi for 5 minutes with zero loss so the case is tight.
I changed the fuel line and filter at the start of the year (probably 25 tanks of fuel). OEM fuel line, Walbro filter.
The carb holds pressure. I opened up the carb and everything looks normal.
I also made sure there wasn't a small hole in the fuel line.
The tank vent is venting properly.

Has anyone had crank seals fail when the saw is a operating temp?

Thanks for the help fellas.

Do yourself a favor and make sure that the oil cap is OFF the machine when you pressure test. If there is a fault on the gasket it may not show up on your test if the vent for the oiler is plugged. Just a thought

 

[qurotro]

Check the crankcase screws too, might come loose just a hair so it leaks when warm, but who knows.

 

[Woodslasher]

The intake manifold bracket is probably warping from over tightening when it gets warm. Farmertec makes an aluminum replacement that is actually a better part than the OEM

+1 I haven't had any issues with the brackets but I'm running an aluminum one in my saw. It just seems like a better design and I needed to order one anyways, so I picked one up and I've run it ever since.

 

[RedFir Down]

Well the problem continues.
I ran about a half a tank of fuel through it on Saturday and it would come out of the cut lean about every 5th cut. It died a few times and was hard to restart.

I've replaced both crank seals, small O-ring as well as the sleeve on the clutch side.
I've replaced the intake mounting flange with an aluminum one like what was recommended.
I've changed the fuel tank vent to an OEM Echo vent.

The saw will hold 8 psi of vacuum and pressure all day long.

Could the carb be going wonky on me?

Thanks in advance.

 

[Matt Ellerbee]

The intake manifold bracket is probably warping from over tightening when it gets warm. Farmertec makes an aluminum replacement that is actually a better part than the OEM

Got a part number or anything? Be good to have on hand I believe.

 

[davidwyby]

Well the problem continues.
I ran about a half a tank of fuel through it on Saturday and it would come out of the cut lean about every 5th cut. It died a few times and was hard to restart.

I've replaced both crank seals, small O-ring as well as the sleeve on the clutch side.
I've replaced the intake mounting flange with an aluminum one like what was recommended.
I've changed the fuel tank vent to an OEM Echo vent.

The saw will hold 8 psi of vacuum and pressure all day long.

Could the carb be going wonky on me?

Thanks in advance.

Try the spray while running trick.

 

[Stump Shot]

Well the problem continues.
Could the carb be going wonky on me?
Thanks in advance.

Could be.
Check the inlet lever height, this needs to be dead on if too low and a little light shows between the gauge and the inlet lever it will run lean.
Once the lever is in its proper place, check the pop off pressure to see if something is wrong with the spring(been changed, is an AM carb, been stretched etc..) If abnormally high replace with new OEM spring.