Stihl 026 - fuel leaking from exhaust

[AngrySquirrel]

plus have you actually checked for a spark or just assumed as new coil?

[spudulike]

9 hours ago, TommyT said:

No you can’t with this particular model of saw. This is about my 6th rebuild and don’t think it’s a carb issue as all three are doing the exact same thing. 

Well all the guys on here say carb and that is telling you something isn't it? If you have rebuilt six of these then you must know that the rest of the engine won't make the saw flood UNLESS you keep pulling it over with the choke ON.

From some of your own suggestions I can see you don't have much of a clue about how it all works.

How about looking at the air filter and finding the choke flap is stuck shut causing all three carbs to not work and flood the machine - how about that.....reckon it may just work!

[TommyT]

I will check the fly wheel key and see if that is still in situ 

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.

 

It’s looking like I will have to strip in right back again and start from scratch. 

[spudulike]

And if it isn't that, then are you pulling the saw over too many times on full choke? Anymore than 5-8 and you risk flooding. If it doesn't pop on the choke then if you have spark, is the flywheel key sheared? What is the compression like? Should be around 160-170 on a new top end.

If all else fails, clear the engine of fuel as Bill said, heat the plug with a plumbers torch, take the air filter off, hold the saw throttle open with your right hand and pull it over hard with your left.

I KNOW IT IS DANGEROUS BUT REALLY.....THIS IS HOW THE REST OF THE WORLD SWINGS AND IT WORKS!

[TommyT]

I have tried pulling it with the choke on and no joy. I stop after a few pulls as it is leaking fuel like mad from the exhaust port. 
The same thing happens without the choke. 
I will take an air filter and carb off a good working saw and hopefully that will lead me where to go. 

[spudulike]

Three pulls on choke WILL NOT flood the engine unless the needle jet is stuck open as others have suggested. Just pressure test the carbs - pop off tester or Mityvac on the fuel line connector and see if it holds pressure.

Seals - I have had saws with NO seals completely that still fire up, top end.....really, three pulls and flooding!

Lack of fuel would be a side effect of lack of compression - you have the complete opposite!

Are you clearing the muffler of fuel when drying the saw?

 

[spudulike]

Just now, TommyT said:

I have tried pulling it with the choke on and no joy. I stop after a few pulls as it is leaking fuel like mad from the exhaust port. 
The same thing happens without the choke. 
I will take an air filter and carb off a good working saw and hopefully that will lead me where to go. 

That much fuel - it has to be needle valve, it is the only logical solution, pressure check the carbs. You are putting fuel in the fuel tank and not down the plug hole when you fill it up

[TommyT]

I’m not pulling in as many as 8 times as there is too much fuel leaking. 

I will check the flywheel key

 

I will change over the carb and air filter from my working saw. 
 

I’ve not got a compression tester but it doesn’t seem as good as the other saws. Maybe the new cylinder and piston is not fitted properly. 

[TommyT]

In the tank only with the fuel

[spudulike]

Lack of compression = NO fuel ....not what you have. It will also not cause loads of fuel to enter the engine like you have.

Here we go, another tip - get a piece of fuel line on the carb that is pissing fuel, blow down the pipe. Does it hold pressure or does it blow through. Suck on it and stick your tongue over the end When you pull your tongue off, does it hold vacuum for a while? I am guessing you don't know what pop off gauges and Mityvacs are.....back to basics!

If this test shows a leak, you either have a leaking carb pump section or probably more likely, a leaking needle valve as we keep saying!