026 tests no air leaks, but runs like an air leak. Leak behind Carb??

[777funk]

It's either an impulse line to carb nipple leak or carb to intake boot. As lean as the saw is suddenly running and how long it takes to rev down from high rpms I know there has to be an air leak somewhere.

Is there a good way to test the carb to intake boot connection?

 

[HarleyT]

Spraying something at the suspected area is a quick way to find air leaks. If you hit a leak, the rpms change.
However an internal blockage in the carb can cause the problem as well.

 

[777funk]

It's now running like it used to once again. I ruled out the carb because it was cleaned and rebuilt not long ago and ran good after the rebuild. I figured it must be an air leak.

I put a layer of silicone on the carb and tightened it back to the intake boot a little tighter than it was when removed. Seems to run good again. Must have leaked there because it pressure and vacuum tested out ok. May be time for a new boot next time there's a problem.

 

[HarleyT]

I did google "Nipple Leak",
but I shouldn't share the pics.

 

[Mad Professor]

Check fuel inlet elbow. Loose or cracked will make it lean like a cracked fuel line, check that too.

 

[Mad Professor]

I did google "Nipple Leak",
but I shouldn't share the pics.

A dirty mind is a terrible thing to waste...........

 

[SteveSr]

It's either an impulse line to carb nipple leak or carb to intake boot. As lean as the saw is suddenly running and how long it takes to rev down from high rpms I know there has to be an air leak somewhere.

Is there a good way to test the carb to intake boot connection?

Do you have the metal insert in the throat of the manifold behind the carb? There is also an aluminum spacer "washer" that goes around the carb mounting bolts between the carb and the boot. If either of these are missing you could get a leak at the carb/boot interface.

 

[777funk]

Do you have the metal insert in the throat of the manifold behind the carb? There is also an aluminum spacer "washer" that goes around the carb mounting bolts between the carb and the boot. If either of these are missing you could get a leak at the carb/boot interface.

I have the rubber boot and the metal insert and then the carb. I don't see a washer. I believe that's how it's always been since I've owned it. It always has changed idle speed slightly based on position but this was different than usual when it was winding down slow and running very lean and fast at high rpms.

 

[sean donato]

It's not really a washer so much as it keeps the intake in its shape and doesn't let it squish around when the carb is tightened. It should have both the outer "washer" (retainer would be a better term.) And the inner ring as well.
Idle speed changing a bit from flipping position is normal, at least with my 026 (well kinda of my dad's now, but that's another story.) Flop it on its side and it changes a little from the upright position. Something about fuel pooling up in the intake.
Look real hard at the the fuel and impulse lines as well. The reason the 026 is back at my house and dad is running my 359 is because of a cracked fuel line. Really I would have missed it if I didn't plan on taking the carb out. Just made me justify replacing the fuel line, intake boot and impulse line. Been about 10 years or so since I rebuilt it. Easier to change them all out now then have to listen to dad complain about it and want one of my other saws. Lol.