Some help needed with Carb Tuning

[Captain Bruce]

Interesting, I replaced part #504724701 which is called the insulation wall. It must have something to do with an air leak because it solved my problem. Furthermore, it was sucking air from where the clip was broken. In my experience any joint/seal past the carb needs to be correct or there will be a leak

It couldn't suck air from the broken tab...the plastic piece that the insulator wraps around? That part goes on the engine , before the carb, as you know. There is no gasket or sealing between the plastic piece, and the intake manifold. When the carb is worked into place, its inner face, presses against the ribs on the face of the intake. THATS the only seal. In more than 1 case, either the intake manifold is cracked, OR the ribbed rubber has degraded, is leaking, OR, the carb isn't tight.

I too fell under the insulator must be a sealing gasket thing.......now we know the rest of the story.

 

[Captain Bruce]

I'm still all ears as to this matter, as it applies to all 435, 440, 445....

 

[Captain Bruce]

I'm still all ears as to this matter, as it applies to all 435, 440, 445....

Heres some pics. The plastic insert, which holds the heat insulator, is not a part of the fuel system. The carb seals directly to the intact manifold.

 

[Homer6679]

The picture attached is a quick sketch I drew up. There is no fastener on the top left of the carb, so therefore there isn’t anything to hold that corner against the gasket. There is a clip on the “insulator wall” on the top left that would hold the carb in place or even pull the carb against the gasket. I also circled the spot where my saw was leaking/sucking air. The only thing I replaced was the “insulator wall” as previously mentioned, my old insulator wall’s clip was broken. The new insulator wall fixed the issue. Therefore that clip must have something to do with sealing. At least that’s my theory

 

[Captain Bruce]

I'll try breaking the clip off, and re-installing the carb, on a working saw. Torqueing 3 bolts with a driver, isn't equalled by a plastic hooked barb. Your new insulator gave you a false solution. Its physics. To clarify from the start, your saw had an issue, you replaced NOTHING but the heat insulator ring, and your saw runs as new???? No other changes; carb never came aprt, etc.

 

[Homer6679]

Sort of correct, I replaced the ignition coil and took the carb apart to check the diaphragms but I didn’t replace any of them. They were in good shape. In the process I broke the clip trying getting the carb off. After reassembly it actually ran worse than before. It Displayed systems of an air leak and confirmed it by spraying carb clean where the clip was broken. The saw would stop racing and bog down when sprayed in that area. After replacing the insulator it ran well