Puddle of Gasoline on ground, coming from airbox...

Hi, 81 xj650h here, again,

Today I noticed a puddle of gas coming out of my bike. It was coming from the tube that connects to the airbox. I opened up the air filter box and there was gasoline in it. It seems to be coming from one carb, the far right one. The choke was on 1/2 way. That might have something to do with it. And the petcock was set to on. I don't know what the deal is with it though. And now I can't stop it from slowly leaking fuel from that one carb. I took the boot off and had a look, but I can't tell what's going on. Maybe a gasket of some kind is broken. I did see a bit of fuel of leaking out of the side of the carb, the metal part that turns when the throttle is turned. I don't know how else to describe it. Any ideas?? I thought maybe I overfilled the tank, but I don't think so because the level doesn't look very high, and I put gas in there like 2 weeks ago and there hasn't been any problem until today. Thanks for reading this.

 

Likely you have a stuck float in that carburetor. It acts like a toilet bowl float, shutting off the gas flow to the carb when it reaches the proper height. Either the float is stuck, the seal for the valve is shot, a float has sunk, or any combination of the three. One thing is for sure, you will have to check your oil level, since gas may have run in past an intake valve and filled the crankcase with gasoline. If so, it must be drained and refilled, after fixing the carb of course. It may be as easy as running some carb cleaner through the system if you are lucky. There is also the possibility that some rust from the tank is lodged between the float valve and the seat, keeping it open.

This illustrates why it is a good practice to shut the fuel off when not riding.

 

+1 MacMcMacmac (hard to type man!) -

 

Yamaha, in their infinite wisdom, didn't provide a fuel shut-off valve on this model. You have ON - which allows fuel to flow to the carbs when a vacuum is present, i.e. engine running. You also have PRI (prime) which primes the bowls after carb maintenence or carbs drained for long term storage. The last is RES (reserve) which allows for fuel to be taken from lower on the petcock filter - the bottom of the tank. Placing an in-line filter helps keep the fine stuff from these old tanks from messing with the carb functions. A bigger problem you seem to have is a petcock with bad seals, as the bike when not running should not leak fuel into the carbs without a vacuum present.

 

Should you be unlucky enough to have a bad petcock and leaking float valves, you run the risk of hydrolock. This occurs when enough gas leaks into the engine and puts a quantity of fuel in a piston coming up on compression. The fuel will not compress and has been known to bend connecting rods and cause general havoc. Fix this problem before this happens and save money!

 

Thanks for all your advice and thanks to 2fast for the heads up on hydrolock. Is there any definite way to know if the petcock is bad? like a test or something? also, what's the next step if the petcock is shot? buy a new one? how much do they cost? Is there anyway to fix it or just replace a seal or something?)

For now I'm going to take the carbs out, clean them, see what's what with the float valves, and then go from there. Thanks again guys.

 

Well the petcock has to be 'bad' to let it flow gas in the on position. I think it needs vacuum to flow gas if it is working.

However, in order for it to get gas past the carbs, a float ALSO has to be stuck...

This scenario lets the gas run freely through the petcock, threw the stuck float into the cylander and drain down into the crankcase. The crankcase gets full and the oil/gas (mostly gas as it floats on oil) goes up the breather hose into the air box.)

clean carbs... clean petcock.

 

Easy test. This will involve running gas, so take appropriate precautions.

Pull the fuel line off the petcock, and the vacuum line. Put a piece of fuel line from the petcock to a container where you can see gas flow, or use clear line. Attach a short piece of vacuum hose to the vac line.

With the petcock set to on, suck on the vac line and gas should flow out of the fuel line, and stop when there is no suction. Repeat on the reserve setting looking for same results. On prime it should flow with out pulling any vacuum on the vac line.

If it flows without vac on the on or reserve setting you need a rebuild kit. Should be about $20 ish and pretty easy to do.

Partsnmore should have one. https://www.partsnmore.com/cat_index.ph ... egory=carb

 

Thanks again woot and 2fast.

This may sound lazy and cheap, But I was wondering if I could install an inline valve in order to shut the gas off while I'm not riding. I would connect it to the fuel line coming out of the petcock. I know I'm being cheap, but if it will work and not look cheasy, than I might do it. But if anyone here says that I'm stupid for doing it, then I'll stop being so cheap and just fix the petcock.

I also want to put a fuel filter in.

Anyway, I'm taking the petcock apart now.

Thanks again.

 

I think the best solution would be to fix the bike

Seriously - a fuel valve isn't a terrible idea - however - what happens next time you forget to turn it off? You'll have to do an oil change and replace the oil filter... that is going to cost more than fixing the petcock in the first place.

The sticking float - well - you should fix that anyhow... might even get lucky and have some carb cleaner be enough.

I'd seriously consider getting your hands dirty (as no one cares about your carbs as much as you do)... you could go to a dealer but that might get pricey.

 

On the petcock, check the diaphragm for cracks and the oring for wear. The cheapest fix I know of that has worked is to stretch the spring, which if weak will keep the plunger with the oring from seating with enough force to stop the fuel.

 

I bought a petcock rebuild kit for 25 bucks from the dealer...Bada Bing.




Kickkem
Indian Territory, OK

 

I dismantled both carbs and petcock. Petcock spring was probably weak because everything else looked decent. So I took BlueMaxim's advice and stretched it out a little bit. I'm going to fix it all properly but for right now I want to just get the bike to where it actually starts, which has been more of a problem than I thought. I looked at the carb in question, and I think that the last owner screwed it up. But I reseated everything and cleaned out the carbs a bit (not a very good cleaning, because they actually looked like they were still in decent shape, no varnish or anything) Anyway, I put everything back on, primed the carbs, and so far so good; no leaking or anything.

There's only one final problem....I still can't get the thing to start. I keep thinking I've figured out, only to find out that my solutions don't solve anything. (Compression is good, by the way) At first, I thought the spark plugs were bad. I pulled them off and found that the wrong type was on, the resister version. I'm not sure if that makes a huge difference or not(but the spark did seem a bit weak.) So I got the new plugs and saw that they sit lower in the cylinders than the other version. So I got excited and said, "that's it." The wrong type of plugs were in. I was wrong though. That didn't really change much. Starter turns and turns and never ignites anything. So I guess it's not getting fuel somehow??

There was one thing that I noticed when I took the carbs off. The boots that connect to the cylinder head seemed to be misaligned. I mean, that's the only way that they could screw on, but it seemed like if the gas was flowing through it, that it would have to climb a gap in order to reach the intake (does this make any sense, I don't know how to explain it). This might not matter at all, but as my very limited knowledge starting to wear even thinner i'm beginning to imagine weird scenarios for why the gas isn't reaching the intake.

One more weird observation to put out there. When I go to try and start the bike after it sits for a few hours, it ignites, revs up for a millisecond to about 1000 rpm's and then dies. Then it will never ignite again untill I let it sit for another couple of hours, when it does the exact same thing. I keep getting excited each time though, as if this time it's actually going to start.


Sorry for making this so long. I've been spending so much time on this bike that I'm becoming obsessed with figuring out what the hell is going on. It's maddening.

Anyway.........anyone got any ideas??

 

Sounds like you've got a fuel problem... perhaps the float heights or maybe a pinched fuel line. I say that because that would be one reason you can crank it and not get fouled plugs AND explain why you'd have to wait a long time to get it to fire for a split second.

SOOOOooo. make sure that the line from the tank is flowing at full capacity... if there is a fuel filter make sure that it is clean.

Then float heights. If they are too low, then you'd have simular problems - however - it would take seconds not hours for it refill the fuel bowls... unless the reason it fires is that the gas drains into the cylanders and in an hour you have enough to fire??? doesn't quite make sense because I wouldn't expect it to do much more than backfire in that scenario.

Start there and give us some more to go on.

Battery charge won't hurt at this point either... infact - that would do it... hangon for a second. If the battery gets weak when spinning the engine, then it won't spark well. If you let a battery sit it will seem to recharge a fraction... maybe that fraction is what lets it spin up... the battery won't charge from the alternator right away so it'll drain it's charge on the spark. If you tap the brakes or the indicators it would probably stall immediately. Then when it sits it gets a second wind.

Charge the battery on a trickle charger for a few hours and see if it fires better afterwards.

 

I'm charging it now woot. I'll see what happens tommorrow. If this works I'm going to praise you for being a God among Men untill the day I die (and I will criticize myself for being an idiot). I don't really know anything about the condition of the battery either. I'll try to start it tommorrow and I guess I could also try to jump start it too. If it's the battery, i'll go out tommorrow and get a new one. Thanks again woot. You are the man.

 

"Battery charge won't hurt at this point either... infact - that would do it... hangon for a second. If the battery gets weak when spinning the engine, then it won't spark well."

I agree, my 85 xj700 had a charging problem, even a new freshly charged battery would only have enough juice for a 1/2 dozen or so times starting the bike before it was too weak to provide proper spark through the ignition system, and the bike would just stall. I have since fixed the problem ( new stator and rotor) and the bike will start and continue to run now... I was amazed at how fast these inline four cylinder motors will zap a freshly charged battery, I actually took the battery back to the dealer insisting that it was bad, they tested it, and found it was good. To my surprise, they were right. I started the bike without the charging system installed and had my voltmeter hooked to the battery and you could just watch the voltage plummet. Another interesting thing I discovered was that if my battery was at 12 volts or below (I believe fully charged should be between 12.5 and 12.75 volts, correct me if I'm wrong), it would crank but not be able to fire. My XJ service manual says when running, the bike will charge between 14.2 and 14.8 volts @2000 rpm's or more. If you charge your battery and it starts up and runs, check whether or not it is charging if the bike hasn't been running in a long time. I may have missed a previous post, but did you just acquire the bike? If so did it run properly when you purchased it?

 

I charged the battery overnight and this morning it started for a few seconds longer than it did before. So I pulled the car around, strapped on jumper cables and tried to start it again. I noticed a big increase in power when I hit the starter button this time. The engine was still hesitating a bit so I sprayed a little starter fluid in it and I finally got it to run. I fiddled around with the idle adjustment screw untill it was a steady 1,500 rpm's and I took it for a spin. So I guess that means that it's the battery. I thought it was alright because it would keep chugging and chugging away like it still had a lot of life left in her, but maybe it's like scotimier said, if it's under 12 volts it will crank but not be able to fire.

I did just purchase the bike and to be honest, the owner didn't know too much about the battery. So I suppose I'll go and have the battery tested to see if it's any good or not. I'm kind of hoping that it's bad because that would probably mean that the charging system is alright. The trickle charger said that the battery was fully charged but it still wouldn't provide enough juice to get it to run. I don't know.

Thanks again guys.

 

Time for my favourite rant. :wink:

Time to check the starter motor. I had the same problem with mine. bought a new battery and it worked fine for two days then was back to starting like a pig. Pulled the starter and checked the brushes. they were knackered. Due to hard to get parts I transplanted a kwaka brush set in it and it has been fine ever since.

Even tried my old battery in there and it still worked adequately.

Basically if the brushes in the starter are not getting a good connection with the armature , the starter will draw too much current from the battery for the ignition to provide a good spark. Over time this extra current drag will be detrimental to the life of the battery.

My suggestion, new battery and strip starter and replace brushes if worn. A light sanding of the armature will do no harm either.

Even if the brushes are good you will notice the difference after a good cleaning.

Cheers
HG

 

Sounds like fuel to me too. The resister plugs will not make any difference in running or not. There is a distinct possibility that you stretched the petcock spring too much and the vacuum does not open it any more, or just not enough. Have you tried turning it to prime (which by passes the vacuum shutoff) and see if that makes a difference. Have you pulled the fuel line off and observed whether fuel flows under any or all conditions?

 

I seem to be experiencing this same problem, when you say might be as easy as running carb cleaner through system...what exactly does that mean? Taking my carbs off and getting the, good with carb cleaner? That, if even possible would be worth a shot as it would be least complicated solution by far...so question is, if I have one or more stuck foats, should I take carbs off amd clean the, again and soak with carb cleaner hopefully resolving stuck issue..? When I took the, apart, I did so completely... Left them together, as far as the four...but took apart the innards of each carb.

Thx,
Ben