Air Box Filled Up With Fuel and Bike Won't Start... any Ideas?

[25knots]

Hey guys and gals.  I need your help diagnosing a problem with my GS.  I think it may have a simple solution, but let me describe it first.

A couple days ago I tried to start my bike without success.  The starter motor was turning the engine fine; there seemed to be plenty of battery power.  Additionally I had taken the bike for a long ride the day before and hadn't had a single problem.

Since the problem didn't seem to be electrical, I was thinking something was going wrong on the fuel end of thing.  So I started taking things off to get to the carbs.  The tank came off, fuel lines too and their didn't seem to be any problems there. 

I took the filter out of the airbox and, low and behold, the whole bottom of the airbox was filled with gasoline.

I think I may have accidentally left the pepcock on "prime" during my ride the previous day.  Might that have caused the problem?

[mimikeni]

Since you have it apart, might as well clean the carbs and check the o-rings for the float needle valves.  Also, make sure your hoses are routed correctly.  They frequently get screwed up when put back together.  Make sure vacuum hose hasn't come loose.

[adidasguy]

PRIME is not the problem, as the floats in the carbs control the fuel flow. PRIME simply bypasses the vacuum and lets gas flow as if there were a vacuum from the engine running.

Most likely you have a stuck float.

Now left in PRIME, if a float is stuck it will continue to dump gas and it will get into the air box and probably the cylinders and oil. If not in PRIME, with stuck floats, only the gas in the hose would get into things and it would seem OK.

However, if a float is stuck (or dirty), when running you will be dumping extra gas into the carbs... it will overfill them .... gas will get dumped into the airbox. If going slow - absolutely. if going all out fast, then you're probably using as much gas as is flowing and the air intake will suck in the extra gas - and you would be running rich.

if in PRIME and you are transporting a bike, the vibrations will make the floats open and bounce around - causing gas to get into the airbox. One reason PRIME should only be used to fill the carbs, not when bike is off or being moved.

Withthat, don't leave in PRIME until you have a chance to check your carbs. Look in the airbox with the filter out. Is one or both carbs wet and dripping? The dripping one(s) will be the one(s) with the floats stuck or dirty. Time to clean the carbs.

[25knots]

"Withthat, don't leave in PRIME until you have a chance to check your carbs. Look in the airbox with the filter out. Is one or both carbs wet and dripping? The dripping one(s) will be the one(s) with the floats stuck or dirty. Time to clean the carbs."

That's helpful, Addidas.  I did notice gas leaking from the rightside carb.  I've got everything apart for a while as I'm repainting the tank (again), so I'll pull the carbs open and take a look.

[25knots]

Update: We've pulled the carbs apart and cleaned everything thoroughly.  The floats didn't seem to be stuck, but they may have unstuck themselves just through all the jostling of taking the carbs off the bike and apart. 

We did find one thing that was curious.  Neither carb had the Needle Jet that goes around the Jet Needle (why someone didn't give either of those better names is beyond me).  I've looked a bit on line and it seems like carbs will run without these.  I also watched a youtube video of someone dissembling gs500 carbs and theirs didn't have the Needle Jet either.  I should mention that my bike has an aftermarket yoshi exhaust on it (from way back when yoshi made one for the bike), and I'm wondering if whether removing the Needle Jets wasn't something one did when retuning the carbs for a new exhaust. 

Anyway, I'm going to order new o-rings and gaskets prior to reassembly, so I've got some time before everything needs to be put back together.  Let me know what you guys think.

[25knots]

update:
since i had the tank off and hadn't check vavlve shim clearance in a while, i thought i'd get in there with my feeler gauge.  in the process i noticed a big problem: the cam chain wouldn't budge at all.  you could life the rear wheel with the trans in first and nothing spun. i don't have a garage, and was quickly feeling out of my depth, so i called a friends, friend who is now a professional dad but used to be the service manager at a motorcycle dealership.

he's had the bike for the last few days and here's what he reports:
the engine was likely locked up because gasoline had likely flooded the engine to the point where the cylinders just couldn't move.  all the problems point back to the carburetor. while i hadn't noticed anything problematic, his eye was more discerning: a lot of the gaskets and o-rings were worn and, the most likely culprit, the needle seat's o-ring was worn to the point where it wasn't sticking tightly into its seat like it should.  this would make gas continue to poor into the bowl.

fortunately K&L sells an inexpensive carb repair kit http://www.powersportparts.net/ProductDetails.asp?ProductCode=4471379 which is a much better deal than buying each piece separately.  I should be back up and running by the weekend.  Also, this round of paint came out much better than last time, with some great pinstriping.  There'll be a photo-shoot to follow soon.

[BockinBboy]

 

I just read K&L, so I'll heed warning.  Many members have reported issues with the K&L needles, and end up buying OEM.  There are a few parts that just require going OEM, and those are one of them.  Since it sounds like you have already purchased them.. decide for yourself what to do for sure, but you might consider returning them before you use them if you can.  You may get lucky with them, but just know there are issues with them you won't find until they are installed.  I guess if you are paying for the work done or your 'borrowed' time from this mechanic is expenive in future IOUs, then don't go through the unknown of the K&L... but again its up to you, I just thought you should have the info.

Here is one member's experience of the K&L needles in his build thread.


http://gstwins.com/gsboard/index.php?topic=59113.msg683699#msg683699



- Bboy

[25knots]

I just read K&L, so I'll heed warning.  Many members have reported issues with the K&L needles, and end up buying OEM.  There are a few parts that just require going OEM, and those are one of them.  Since it sounds like you have already purchased them.. decide for yourself what to do for sure, but you might consider returning them before you use them if you can.  You may get lucky with them, but just know there are issues with them you won't find until they are installed.  I guess if you are paying for the work done or your 'borrowed' time from this mechanic is expenive in future IOUs, then don't go through the unknown of the K&L... but again its up to you, I just thought you should have the info.

Here is one member's experience of the K&L needles in his build thread.

Thanks for the advice.  The K & L kit is already ordered so I'll try it out and, if I do have Carb problems, I'll at least have a good idea of the culprit.


http://gstwins.com/gsboard/index.php?topic=59113.msg683699#msg683699



- Bboy

Thanks for the advice.  The K & L kit is already ordered so I'll try it out and, if I do have Carb problems, I'll at least have a good idea of the culprit.

[RossLH]

I just read K&L, so I'll heed warning.  Many members have reported issues with the K&L needles, and end up buying OEM.

Been there, done that. Used a K&L rebuild kit, set the floats, put everything back together, and one side wouldn't seal. Literally got zero use out of it before the float needle started leaking.