All 4 carbs flooding?????

[Sidecar Bob]

When I brought the 'Wing around from the shed lo these many weeks ago it didn't want to start and I smelled gas so I removed the air filter and saw that there was gas on the bottom of the plenum. I turned the gas off and it fired up right away and ran on the gas in the carbs to drive around to the front of the garage.

It has sat there since while I dealt with other projects but now I have some time to work on it so I pulled the carbs, hooked them up to a hanging fuel tank and watched while gas ran into the plenum from all 4 carb throats. So I drained them, removed the float bowls, dropped the floats and inspected the needles (they all look good to me), then carefully measured the float heights (all were correct) while re-assembling them.

And it did the same thing again.

Any ideas?

BTW: It has a '79 GL1000 engine & carbs.

Also: I have the tops of the carbs off. That shouldn't make any difference, should it?

[CYBORG]

Fuel seals between the plenum halves

[Sidecar Bob]

I was kind of thinking along those lines.... I guess I will have to split the plenum to find out

[olchris]

"watched while gas ran into the plenum from all 4 carb throats" That is weird..... Plenum gasket was my first thought but fuel coming from all 4 "carb throats"..... Are your sure?????
IMO Your that far in now, split the plenum and do the lot if it a keeper....

[zman]

If you have the slides out you can see the needle hole so If it is coming from the bowls overfilling it sounds like it would be the floats overfilling, . If you haven't I would just buy 4 new needles. The rubber can swell or the needle springs get weak and dont give a positive seal ,if your bowls are over filling and your floats are set right I cant imagine it being anything else.

[ericheath]

Chased the same a year ago. I think it was RB who suggested pulling all the slides so you can see where it comes from. If you look you'll see if it's up through the jets or from the throat on the plenum side.

[RB]

Yep that's the way to Id the source. Unusual all four..though..paper in the plenum also helps show where/which carb(s) it's coming from. you have to be looking as you turn the fuel on...

[Sidecar Bob]

OK, this is truly strange. Yesterday I was sure that I saw gas coming from the jets of all 4 carbs. Tonight I tried it again with a piece of paper on the bottom of the plenum and only the #3 was wet. So I drained them again, removed its bowl, sat them on a block so that #3 was hanging over the side above a container, held the float up and turned the gas on.

I can now say that the float valves are all OK. The gas appears to be coming from the throat of #3.

[robin1731]

Carb to plenum o-ring?

[Sidecar Bob]

Yep. I separated the plenum and detached carb #3 and I could see deep cracks in the carb to plenum seal before I pulled it out of the hole. So I detached the other 3 and their seals were not much better.

In 2008 I replaced the original rubber parts in these carbs with a Randakk kit so these were supposed to be the best seals available. It looks like the rubber reacted to the fuel (or maybe the ethanol in it?) and swelled. The holes in the centres of them are significantly smaller than they were when they went in.

This could explain why they all leaked to start with and then only 1 leaked: After they were in contact with fuel they swelled up and sealed but the cracks in that one seal were too big to seal.

When I rebuilt the carbs I tossed the original ones (probably the only original rubber parts that were not hard & brittle) into a drawer of used small o-rings and they were still there when I looked tonight. In fact, there were 6 of them because the petcock uses 2 (note to self: check the ones in the petcock too). When I go out for errands tomorrow I will see if I can get some Viton o-rings that will fit and if not I will re-assemble them with the original seals.

[zman]

Thats the D`rings your talking of, dont know if the regular O'rings will work, the D rings are fatter then the same size in O'Rings..they do still sell the D`rings in Viton, not sure about in the great white though.

[Sidecar Bob]

I figure 9mm O.D. x 3mm rings should seal pretty well. The space they have to fit in is about 2.5mm deep. If I can find them.....