walbro carb

[400brian]

I find myself in the hole with a WR7-5 Walbro carb.
I've had the 72 400 running, but its way too rich. It all started when I first tried to fire it up...it made a snort, which was quickly smothered out by fuel running everywhere. I took it off, disassembled, and lowered the metering lever so that it "just" deflected when a straight edge passed over. Put it back on...engine fired right up. Let it run for a while, exhaust sprayed black goo all over the engine shroud, secondary sheave, tunnel...grrrrrrrrrr.

A few hours later, I went to fire it up to put a timing light on it ( I have timing issues as well ). cranking with the e-start, fuel started running out the air bleed at the base of the tube the high speed needle is in. Pulling it over by hand it was OK, but at starter rpm it is running gas all over my freshly painted tunnel.

Its not supposed to do that!

I just pulled apart another WR7-5. Clean as a whistle inside, covered with crud on the outside. The metering lever appears to be set just as high as the first carb.
I've measured the metering diaphragm and the button in the center of it that mates to the metering lever ( windrosa ) it seems very similar to the original. I'm trying to figure out why the first carb is pushing fuel out the air bleed. I've never personally had this issue before.
I'm going to bolt the second one on and see what happens.

[lwb140]

good luck let us know how it goes wade

[400brian]

I may have found the source of the problem late last night, after starting this thread.

Hopefully will have a report later today.

[400brian]

It appears that installing the thick gasket that is supposed to be between the main carb body and the metering diaphragm, cured the problem. The original Walbro gasket/diaphragm was a single unit. I've managed to do this correctly in the past, but on this carb I was "doing it by the book", and the manual shows the single unit, thus the confusion.

[400brian]

Perhaps I spoke too soon. Once again, progress made in the afternoon is taken back in the evening.
Cranking the engine with the starter had gas running out the bleed just as before. What's worse, I never did get it to start.

[johndeerejamie]

this is the issue im going through on mine. is gas spitting out the rear of the carb?
mines a wda 31 so im not sure how similiar mine is to yours but i couldnt figure it out, i seem to think it may be plugged somewhere so im gonna soak it again.

[400brian]

The carb used on the 72s was a bit different. The newer carbs don't have the air bleed hole I'm referring to.

The fuel is spewing out the throat.