Two carb problem questions

[John in MA]

OK, just a couple quick questions:

1. The carb (HA-135) on my XL-98 has been leaking since I rebuilt it. I don't know if it did before, becasue the saw was too messed up to put gas in. Anyway, after pulling the rope and getting gas to the carb, the gas starts dribbling out of the barrel. What might this be? Everything has been replaced, including the main needle valve. I really want to get this pain taken care of.

2. My Stihl 032ave just started dying at high speed. It'll run for about three seconds wide open and then it'll die unless you return it to idle. I've never rebuilt the carb on it. It's probably running with the original diaphragms. Am I correct to assume the fuel pump isn't delivering enough fuel?

Thanks in advance.

 

[rupedoggy]

I don't know about that Homelite. That Stihl 032 sounds like a screen plugged up. There is a small screen under one of the carb plates. Take off the plate and clean that screen. Then you will get enough flow to run faster than an idle. Mike

 

[sonny]

sounds correct on the 032, on the other you sure the fuel line is not leaking.

 

[John in MA]

Thanks. I changed the screen in the Stihl and that didn't work, so it's off to get a carb kit.

The Homelite actually has new fuel lines. No leaking there. It's just after you crank it. The gas starts running out the barrel. I've been over it several times and I can't figure out what's up.

 

[Walt Galer]

Howdy,

The gas running out of the "barrel" of the Carburetor is due to a stuck open inlet needle in most cases. This can be caused by something between the needle and seat, (not likely) or by an incorrectly installed atmospheric pressure diaphram. (Most common, especially if the mechanic was inexperienced). The problem happens due to putting the little rivet in the centre of the diaphram on top of the inlet lever to the needle, instead of putting the forks on this lever around the relief in the rivet that engages it so the diaphram can work the inlet lever up and down, openning and closing the needle as needed.

The lever must be shaped so it is lying parallel
to the floor of the chamber. If it is bent upwards, that also will hold the needle open, even if the diaphram was correctly installed.

Regards,
Walt Galer

 

[John in MA]

This is really starting to mystify me. I checked the needle valve lever and the diaphragm pin engagement. No problem there. The needle valve seats well and seals tight.

Next?

 

[Walt Galer]

Howdy,

Well, here is one more to try. I have run into cases here locally of Honda motors on outdoor power equipment at a local rental, repeadidly flooding out. When I recommended they quit using 87 octane Exxon fuel, and change to 92 octane Conocco, their problems went away!

It seems the excessive high vapor pressure of the poorer gas was blowing the inlet needle off seat, over-riding even the float! I have also seen this effect on rototillers in Tenn. when I lived there. A plugged up tank vent can be at fault, or it just may be darn poor gas with excessive vapor pressure/volitility as sometimes seen with 87 octane fuel these days.

Regards,
Walt Galer