No gas getting to the engine of a 1983 GS450E?

[Synthead]

I'm a little stumped on this one at the moment! To the best of my knowledge, the engine isn't getting any gas. It cranks and cranks, and there are no signs of it combusting. I removed the spark plugs and connected them to the bike and there is a spark on both cylinders. I checked the fuel petcock (which is new), and the on and prime positions do with they should with the vacuum, and the prime position does drain fuel. I recently rebuilt the carbs and the bike has been running wonderfully for about three months. At first, I thought it was flooded, so I removed the plugs and cranked it, but I could hardly smell any gasoline from the cylinders, and there certainly wasn't any gas spraying out.

The only thing that I've changed which might matter is that I've added Lucas air filter oil to my foam filter. It's this stuff. I heard somewhere online that you want to lightly soak it, then squeeze out the excess. Could I have added too much, and maybe it's plugging the intake? Could this keep the air from pulling fuel in from the jets? I couldn't imagine something from Lucas would be problematic.

Other than that, I'm stumped. I was thinking that my float valves could possibly be stuck, but I've never had this happen, and I recently rebuilt the carbs, anyway. I've done this multiple times before, and it's been running great for about three months, so I couldn't imagine this would happen all of a sudden.

Any thoughts?

[Big T]

You rebuilt the carbs?
what method did you use?

[Synthead]

This is a bit of a backyard way of doing it, but I took them apart and removed all the rubber parts, then boiled them in water with lime juice. I've done this before on some KZ1100 carbs and it worked great. When I took them apart, everything looked super clean, but I figured I might as well clean them out anyway, since I removed them and took them apart. I also replaced the passage plugs while I was in there. All the gaskets and o-rings were good, too, so it might have had a recent-ish rebuild.

But even so, it's a twin, so it seems like it would be really weird for both carbs to have the exact problem at the exact time. I would at least expect it to run *@%^$*@%^$*@%^$*@%^$ty on one carb if a carburetor was totally plugged. And if it was a problem with the vacuum line for some reason, wouldn't setting the petcock to prime bypass this issue? Pus, it's been running great for three months.

[Brendan W]

I would open a float bowl drain screw with the tap on prime and catch everything that comes out in a jar.
Leave it run for ten seconds or more. Dirt can get hung up in the float valve and by dropping the float fully the gap opens enough to let it through.
If the flow looks too little or nothing comes out, a gentle tap with a rubber mallet can help get it started.
Keep checking what you are or are not finding in the jar, debris or water etc etc.

[rphillips]

Ran good for 3 months now neither cyl. will even try to start. What Brendan said to be sure fuel is in the bowls. Both carb needles wouldn't stick closed at the same time, Oil on air filter may make it get too much gas, but not too little. Quickest thing, give it a shot of starting fluid to see if it runs on that, just to be sure be sure it is a fuel problem.

[Synthead]

Thanks a ton for the ideas! So that's what the float drains are for!

After lots of cranking, it finally started and ran fine, so maybe there was a little water in the tank or something? I smacked the carbs with the end of a wood handle before it started, too, so maybe the floats were stuck closed? I hate having this kind of problem be such a mystery, but I suppose I'll keep my eye out for this in the future.

[rphillips]

Congrats, glad it's going again. But Dang it, if you see & fix the problem, you know what, why, & if it may happen again. But this way you still don't know "for sure" what it was, why it happened or if to expect it to happen again. I rekon if it does, first thing will be pecking on carbs. Oh yeah, You said after a lot of cranking, If happens again, be sure it's on PRI when you do the pecking then wait a minute or two for the bowls to fill. If on ON you will need to crank it long enough for the vacuum to hold the pet cock open to fill the bowls