Some Carb Strangeness

[Pain]

So I was out on the new 1981 H yesterday, and decided to stop for gas (170 miles on the trip, farther than I had ever gone on one tank before. Little nervous that I had not hit reserve yet).

I put in 5.1 gallons, and might've over-filled the tank a little. Paid, and the bike wouldn't start.

Pushed it out of the gas-pump area, and take quick look. Can't see much with all that plastic on, and I don't have any tools, but I smell gas. And I see gas, dripping from the air filter box.

I take the box off, and there is and inch of standing gas in the bottom. I dump it out, out it back on, and the bike starts right up. I just think "ooookay," turn the bike off, and go in to wash my hands.

Come back out, out the stuff back on, and the bike won't start. Again, a small dribble of gas from the air filter case. Again, an inch of gas. This time I start the bike without replacing the cover, and the further right carb has a small stream of gas coming out.

Now, I did mention no tools, but not too far from home, and the vintage bike garage within walking distance of said home, so I figure I will just get the bike there, and let them deal with it. The really do good work, and while I can clea carbs, and I not sure I would notice something wrong.

The bike runs kinda rough, but it does run, and I just take it easy. After a mile or 2, I am smoking a lot form the right side, and pull off to make sure the bike is not about to blow up. the smoke is coing from the right exhaust. All four cylinders are hot, and I keep riding.

Another mile, and the Interstate onramp for home. I open up the throttle a bit, and notice the bike repsonds just fine. Doesn't seem to be smoking either,

Exit where I should, and hit the first parking lot. No smoke, no gas dribble, bike runs like nothing was ever wrong.

I let it sit for a while, come back later. It starts right up, nad I drive a round my neighbourhood, just to see if I can get a reoccurance. Nothing.

So.... Is this a "Too much gas in the Tank" thing (Which I can't see, but???), or do I have something about to majorly fail? I am not sure what to look for on my own, and while I do believe in supporting my local shop (hee hee, The Shop), I am not too keen on paying for a non-problem.

Any pearl of wisdom would be appriciated, but ones referring to my issue would be the best.

[xssiveone]

Sounds to me like you got a tiny piece of dirt or something holding the float valve open in the right carb. Of course, this "shouldn't" EVER happen (yeah, right!!) because you have the screen filter in the tank, and also the tiny screen above the float valve in each carb. Might be time to think about inline filters.

[MAXIMAN]

xxsiveone is right. Probably a little piece of trash stuck in the float valve and when you started riding it flushed out of the seat.

I fill my XJ11 up to the brim alot and it never does that. However if you suspect gum or varnish build up beggining in the float valve run a can of Seafoam through the fuel and see if that deosn't help. If not you may have to replace the float valves and float seats.

Good luck

[MAXIMAN]

One more thing. If you EVER suspect the float bowls have overflowed for a very long time, you might wanna change your oil.

This happened on Kong when I first got him. I figured the gasoline not only flowed into the airbox but also the other way...into the cylinders.

Sure enough when I drained the oil it had a faint odor of gasoline. I dunno if that is enough to damage anything but I tool no chance.

[TopCatGr58]

Hey there Pain,

Well, I hate to point out another problem, but aside from the float needle valve getting stuck, with the "H" model, there shouldn't have been any fuel flowing into the carbs with the bike turned off, cause there wasn't any vacuum going to the petcocks, and so it shouldn't have kept flowing into the carb to flood it, SO.... you may also have a problem/leaking petcock that feeds the right bank.

You may want to investigate the petcock and possibly rebuild it to prevent it from leaking while the engine is off, that will help to reduce the chance of flooding the carbs if/when the needle valve gets stuck again.
T.C.

[skids]

reconditioning the petcock?

One thing you can do is to order a couple of holey rubber gaskets for the petcock, or bite the bullet and get a couple of kits.

You can drain the gas out using prime and rout a hose to a gas can. Then, take the petcocks apart. Keep track of which one goes where, as there is a right handle and a left.

Examine the holey gasket. If there are any gouges from hole-to hole, it can leak. Sometimes you can rotate the gasket so that the damaged holt is up(? I think).

Take the valve handle and polish it (contact surface) using fine grit emerory paper, followed by mother's milk polish. I slightly smoothed the sharp edges around the holes. Those surfaces are rough from the factory mill.

Bend the wavey washer so that it is effective again, if needed.

Take the diaphragm assembly apart, noting the location and allignment of the breather holes in each layer. Now you have access to the plunger and conical hole that the oring seals. Do what you can to clean the conical surface so that a good seal is made when the bike is off. I recommend polishing it.

The Plunger Oring may need replacement, but if you don't get a perfect oring, it won't seal well. Examine the diaphragm for holes. I do NOT recommend that you stretch out the spring like I did on one of mine (at least not much). I had trouble at highway speeds, with the associated carbs starving for fuel.

There is a one-way valve in the assembly that is near the nipple for the vacuum hose. Make sure that it is clean and clear.

The filter towers can detach themselves or become clogged, or the top caps can come off. You will have to remove the petcocks from the tank if you choose to clean the towers. If you do, the mating gasket may need to be soaked in mineral oil to help "puff it up again" and cleaned. Those have been squashed for so long, they may be deformed enough that they will no longer seal against the tank. The screws have fiber washers to help seal the works. Be careful with them, or get new ones (substantial ones). It may be a good time to rinse the tank with the petcocks off and the filters out of the way. I would use gas or mineral spirits (less flamable).

[skids]

The petcock problem is not the only problem. The valve at the float is also a likely culpret OR you have some leaking going on at the float valve's oring (the valve has an oring around it and it is pressed in place).

One thing you can try if it still gives you trouble is to drop the float down and flush out the valve:

Bike off, petcock to run, open valve at bottom of float bowl with a screwdriver and catch fuel in tuppaware (your wife will kill you), turn the cock to prime and flush out any particles, turn the cock back to run, close the bowl drain, turn to prime to fill it back up, and with the air filter off, check for dribbles. Turn it back to the run position.

[Pain]

I love this site.

I just rebuilt some petcoks, so I can do that. There was no leaking with the filter cover off and the bike not running, but hey, I hate breaking down.

Oil was just changed prior to the trip after purchase.

Going to find some Seafoam now.

Thanks all.