Flaky float valve.

[jmerlino]

Ever since I got my R100, I've been having problems with the right side carburetor. Up until recently, the problem has been that sometimes when I take the bike out, when I first open the petcocks, the carb would leak fuel. If I took off the float bowl and tapped the float a couple of times, it would stop, and then it would be fine.

Yesterday, a new dimension revealed itself. I made a stop on the road, and I didn't close the petcocks when I shut the bike off (I was only planning to be a few minutes.) After a couple of minutes, I saw a guy run over to my bike and shut off the petcocks. This was the first time it had leaked after the bike had been running.

So I did the tapping the float thing, and all appeared to be well, until I started the bike and rode off. I got a couple of hundred yards, and then the right side cylinder died. I pulled over, and sure enough, there was no gas in the carb at all. I tapped the float again, and all seemed to be well.

The same thing happened to me again today. It doesn't appear to be a huge problem, but it is irritating, and it does spill gas, which could be potentially dangerous. And it would really suck if this were to start happening when the bike was running.

So... any ideas as to what's causing this? Is it just a sticky valve?

[PGlaves]

The float needle is binding in the seat bore for some reason - and seems to be sticking in either the open or closed position as it sees fit.

So - you need to thoroughly clean that needle bore and seat. It is probably gummed up. Clean the outside edges of the needle too. And if it has a neopreme tip (it probably does) make sure it isn't deformed or worn.

[jmerlino]

How hard is this to do? (I downloaded the exploded view of the carb from the Bing website, so I have an idea of where the float needle is.) I have never done anything like this before. Is this something I can attempt and be reasonably sure of success? It looks like I could do it with fairly minimal disassembly of the carb.

[jmerlino]

So here's what I did: I did NOT remove the carb from the bike. I DID remove the float bowl and the float, and the float needle. I gave the float needle a good cleaning with Simple Green. I took a pin and did what I could to clean the bore. I put it all back together and opened the fuel line. It did not leak. I took the bike for a short ride, and when I got back, I left the petcocks open. Again, no leaks. This by no means proves that it's fixed, but I'm cautiously optimistic.

In other news: (File this under "the joy of a used bike") I'm discovering that some of the quirks in my lighting system have to do with attempted modifications on the part of a previous owner. Hopefully, I'll get them all disentangled before too long. Evidently, he installed Run-n-lites on the rear turn signals (but not the front), and may have reversed the wiring on the tail and brake lights.

[jmerlino]

Bah. It's not fixed. Leaked again yesterday.

[jmerlino]

Further update:

Took it to my "local" indy dealer/mechanic (who sold me the bike). We replaced the float needle. He looked at the old one and said, "This looks brand new." Once the new one was installed we opened the petcock, and sure enough, the thing starts leaking all over the place. His helper opined as how he thought it might be a particle of crud wedged in there. He took the bowl off and said that he saw something floating in there, which he believed to be the offending particle. Never the less, he took a look up into the bore and pronounced it and the needle seat to be clean. We reassembled everything, and this time there was no leakage.

One thing the dealer did comment on was that the float itself was out of adjustment. I believe that this was done when I took it for a tuneup to the "non-indy" dealer. I told them I wanted the float valve fixed, and they said they "adjusted" it. I believe that this is what was causing the needle to become jammed in the shut position, because it looked like the way they had the float adjusted, it'd be pushing the needle up there pretty hard. Needless to say, I'm a little irked at the "non-indy" dealer, becase it would appear that instead of taking a look at the carb to see what the problem actually was, they just made a stupid assumption and went with it.

So once again, I'm cautiously optimistic.

[pmdave]

Crud entering the carb can definitely cause problems. I always install a clear plastic filter in the lines, both to catch the big chunks, and so I can see what's happening. Old fuel tanks tend to start flaking the interior coating, which both collects in the screen above the fuel valve, and goes through the screen (if small enough) So, I suggest draining your tank, removing the fuel valves, and sloshing some gas out the bottom to flush out any loose crud. Make sure those little screens are in place over the fuel valve tubes.

Second, old fuel lines can begin to disintegrate internally from old age. Every few years you need to get a couple feet of new fuel line and change them all. That's advice from the Bing man. My advice is to find a snowmobile shop and buy some exotic snomobile fuel line that seems to be indestructable and remains flexible at severe temperatures. I think you want 1/4 in. but check the fitting size.

Third, the foam floats were designed before today's alcoholic fuels and aggressive additives (that tend to soak into the floats) So, if your floats are the originals, they might be sinking, which could explain why the other guys bent the float tabs. With the tabs bent at an angle, the needle gets pressed against the side of the hole, and stays open. Two fixes: change the floats for new(er) ones. Or, change the bowls and floats to the "alcohol proof" setup. See the Bing guys, and chill off your credit card so it won't catch fire.

Finally, always shut off the fuel valve when parked. Some valves can be rebuilt--basically changing the rubber valve disk and lubing the lever so it turns freely. Some valves can't be rebuilt. If the valve is hard to turn, at least try squirting some WD-40 around the head of the lever to clean out the crud and lubricate it. If it's hard to turn, you tend to avoid using it.

As you've discovered, old airheads are there to keep us from having to do all those important yard projects.

pmdave :type

[jmerlino]

Well, the carb has not leaked or stuck shut since the indy guy had his way with it, so I'm tending to think that it's fixed.

I am planning to rebuild the carbs and replace the fuel lines at the end of this season, so that stuff is definitely on the agenda. I do have filters on both sides of the tank, so I'm tending to think that it was something that flaked off the side of one of the lines. I like the snowmobile shop idea.

As you've discovered, old airheads are there to keep us from having to do all those important yard projects.

I never liked yard work much anyway.

[WooDmEn]

Rebuild (or have them done) the carbs. Get the Bing "independent float and bowl" kit. You MAY have to have the Bing fellow ream or replace the float needle seat; this can only be done by Bing.

[The_Veg]

The independent floats are WAY more fiddling than benefit. Those were designed for aircraft that spend a lot more time leaned over than do motorcycles. Unless you ride in small circles, you'll never be leaned over long enough at a time to need them.

[WooDmEn]

I disagree with that; the independent floats are NOT subject to rising and falling due to the bike's acceleration, which makes the engine run rich for 10-15 seconds everytime one accelerates - accelerate, gas sloshes to the rear of the float bowl, floats go down, fuel is introduced (unneeded fuel) to the float bowl, and when the bike stops accelerating, the engine runs fat, needlessly. Fiddly? Not at all. One they are installed - quite easy if the carb is off the bike - and the level is adjusted one time, that's it for life. I've got the kits on all my airheads; they add 2-3 mpg, too. And they are stronger at shutting off the fuel if you leave the petcocks open.

[jmerlino]

accelerate, gas sloshes to the rear of the float bowl, floats go down, fuel is introduced (unneeded fuel) to the float bowl, and when the bike stops accelerating, the engine runs fat, needlessly.

I have a tough time buying this. The float takes up nearly the entire area of the bowl. If gas were indeed to slosh to the back, I would think that would tend to make the float go up rather than down, as the fuel level in the back of the bowl was to rise. (I mean, unless you're accelerating so hard that all the fuel is plastered up against the rear wall of the bowl - in which case it's probably not getting into the jets anyway.) Plus, when you're accelerating, you have the throttle pretty wide open, which means that you're using lots of fuel, which means that the float valve is going to be open anyway.

In any event, the floats in my carbs seem to be fine. I think a good rebuild/cleaning and new fuel lines should have my fuel system in top shape.

[pmdave]

Someone made a quick left turn onto a different road.

My point about the plastic bowls and floats is that THEY DO NOT SINK, DISSOLVE, OR CORRODE.

Fiddling? what fiddling? same fuel level adjustment as with the stock floats. Pull 'em out of the box and stick 'em in. Do they provide better fuel mileage, less sloshing, etc.? I don't care much, as long as they don't SINK.

OK?

pmdave :blah

[jmerlino]

Someone made a quick left turn onto a different road.

My point about the plastic bowls and floats is that THEY DO NOT SINK, DISSOLVE, OR CORRODE.

Fiddling? what fiddling? same fuel level adjustment as with the stock floats. Pull 'em out of the box and stick 'em in. Do they provide better fuel mileage, less sloshing, etc.? I don't care much, as long as they don't SINK.

OK?

pmdave :blah

That much I'll buy. If it comes to the point where I need to replace my floats, I'll certainly consider the plastic ones, but FWIW, I DON'T think that's why the mechanic adjusted it. I think he did that so that it would jam the float needle up into the seat and stop the leaking. And I think that was a real crude and brute-force approach to the problem which A) didn't solve it, and B) created another one.