Stihl 026 - fuel leaking from exhaust

[Tom Stitt]

I have just rebuilt another 026, but this time round it has fuel oozing out of the exhaust. It has a new piston, rings and cylinder. New exhaust gasket.
I've tried three different carburettors all with new carb kits, but exactly the same result. When I take off the carb the impulse line runs with fuel for nearly a couple of seconds.
Could it be that the piston rings are not seated correctly?
Any advice would be really helpful.

 

[mike-s]

The impulse line should be completely sealed at the carb end - it just goes to a flexible pump diaphragm. With a good carb, there's no way for fuel to get to it. Bad diaphragm, or it's installed wrong.

 

[Tom Stitt]

The impulse line should be completely sealed at the carb end - it just goes to a flexible pump diaphragm. With a good carb, there's no way for fuel to get to it. Bad diaphragm, or it's installed wrong.

I’ve changed the impulse line when I rebuilt the saw. I’ve changed three carbs all with new kits. I’ve even went and double checked that the gaskets and diaphragms were on the right order and way. Have rebuilt numerous saws but this is a first.

 

[rupedoggy]

It's flooded

 

[Andyshine77]

It's flooded, or the metering valve on the carb is pushed or stuck open. The valve can be held open if the lever is too high, or the carb diaphragm and gasket is reversed.

 

[Tom Stitt]

Would bad crankcase seals cause this issue, as it does seem lower on compression than my other saws I rebuild. It’s a rocwood cylinder piston kit.

 

[RED-85-Z51]

Does it actually start and run?

Sent from my LM-G820 using Tapatalk

 

[Tom Stitt]

No it doesn’t and isn’t even close to starting. I don’t think it’s a carb issue as all three carbs are doing the exact same thing.
This is probably my 6th rebuild of this model of saw and never had this issue before.

 

[SteveSr]

No it doesn’t and isn’t even close to starting. I don’t think it’s a carb issue as all three carbs are doing the exact same thing.
This is probably my 6th rebuild of this model of saw and never had this issue before.

Will any of the 3 carbs hold 7-10 PSI at the fuel inlet?

 

[RED-85-Z51]

Does it do anything after clearing the flood..and removing the muffler...and trying to start?

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[Tom Stitt]

I’m going to borrow a carb compression tester, but all three having the same issue after been ultrasonic cleaned and a new carb kit installed seems odd. That’s why I’m starting to think it must be something to do with the cylinder, piston or seals?
After removing the muffler and carb and blowing everything dry with an airline it does the exact same thing. Not even trying to start, but within three pulls it is ozzing fuel out of the exhaust port.

 

[jltrent]

Take a carb off one of the 026 running saws you have rebuilt. If flooding it is the metering in the carb hands down. The kits you have have the wrong diaphragm in them.

 

[drf255]

Do you have spark?

Is flywheel key in position or sheared?

If you went with an AM P&C, you may have such low compression that the saw won’t run. The AM crap can be out of round or have huge squish. Coulda given you 44mm rings for a 44.7 jug. Anything possible.

You need a minimum compression for a saw to start. You may just be pulling and pulling with no firing and hence flooding.

 

[Tom Stitt]

Ihave to thank everyone who took time out on my saws issue.
Guess what the forum here said it was the needle valve and I was thinking that three carburettors can’t possibly have all the same problem.
THEY ALL DID!!!

I bought a number of various carb kits last Autumn and have found out the hard way that I have mixed up two lots.



Huge thanks again to everyone.


Tom

 

[chilipeppermaniac]

Ihave to thank everyone who took time out on my saws issue.
Guess what the forum here said it was the needle valve and I was thinking that three carburettors can’t possibly have all the same problem.
THEY ALL DID!!!

I bought a number of various carb kits last Autumn and have found out the hard way that I have mixed up two lots.



Huge thanks again to everyone.


Tom

Yup, I figured, Operator ( mechanic) error, since all 3 were doing same thing.
At least it was a chainsaw and a non running one at that. I was riding my Harley on a trip maybe 150 miles from home, The bike ran fine for maybe 300 miles of riding until I was 1/2 way home one night and noticed gas was pouring out of the carb when I had come to a stop. The scary part is I could not figure out how to make the fuel stop dumping, and of course hot exhaust and surely tons of gas fumes. I luckily made it to my buddy's house and he essentially maxed out the throttle back and forth a bunch of times with the bike off, and then started it up again. I think he said the needle valve must have been sticking. Anyhow his trick worked.

 

[Tom Stitt]

Thanks everyone from a guy starting off that was looking for friendly advice.

 

[chilipeppermaniac]

Glad you got it sorted out, from one novice to a fellow "starting off"member.