Bike does not stay running

[wildbill]

Ok so there are plenty of threads in here that i have read but still have not found a solution to my problem. My bike was running all fine and dandy until i went to take it out one morning. I put the choke on, started it, it started to warm up, after a few min i lowered the choke a bit and off i was. I got to the end of the parking lot and my bike died. I played with the choke and that didn't help. The battery eventually died and the next day i tried jumping it with no luck.

Some things that will help to know.. Its a 95, 13k miles, has a yoshi exhaust and lunchbox, its jetted with Buddahs kit. I did the valve clearance 4k miles ago. I set the floats and i was pretty sure i did them right but when i put it all back together i hear a little back firing when above 4k RPM with closed throttle. So i know i am running slightly rich, I've been riding the bike for about 3k miles now w/o problems. I checked the spark plugs and they are black, not terribly but i changed them out anyway since they were over a year old. The day before my bike stopped starting i was going about 80mph and my bike started bogging down, i switched to RES and it still didn't help, i pulled over and set it to PRIME and it seemed to fix my prob. My first thought was the petcock is going and im not getting fuel b/c i still have half a tank left. The bike bogging down happened a couple times prior to this incident, both times when i was riding hard at 9-10k but when i backed off to lower normal rpm range the bike ran normal again. Could i have a valve/piston problem?

My thoughts as of right now is that im not getting fuel to the carbs, my next step will to pull the tank and check all the hose routing and make sure everything is connected. If anyone might know what my problem is if its not the fuel lines your help is much appreciated.

[DoD#i]

Did you try prime when it died and wouldn't start? You don't specify.

Stick a 1/8 inch fuel hose on the carb drains (or just hold a small can directly under them) and drain out what's in there. Bet some of it is grotty.  If your petcock is set to reserve, you'll just get what is in each carb bowl. If you then set to prime, you'll know if gas is getting to the carbs on prime, since the bowls will either refill, or not.

If you use clear 1/8 inch hose, you can check the float level as well.
http://www.bbburma.net/FloatHeight.htm


Check the fuel lines, the carb vent line from the upper tee, and the vacuum line for the petcock.
http://www.bbburma.net/FuelHoseRouting.htm

[ke7syv]

Did you try prime when it died and wouldn't start? You don't specify.

Exactly. Prime basically turns it into a gravity fed system compared to a vacuum controlled. The engine creates the vacuum used to hold open the valve, but a tiny hole in the diaphragm can lead to failure. Turn it to prime, wait three seconds then give it a go. Choke if needed, of course. 

[wildbill]

ok so ive left the petcock on prime. checked the carbs, they are getting gas.. one float is off even though i set them afew months ago. the fuel lines are pretty new, got them about a year ago and they look fine. the carbs have new vacuum o-rings when i rejetted the carbs i put them in. the battery is only 2 months old and i could jump the bike but would not turn over. So i bump start the bike in 3rd and after a few tries got it running for 10 seconds and then it dies, got it running afew times both times only for a matter of seconds until it dies on me. i have the choke on. im really puzzled by this one. i was thinking it was the starter motor but even when i get it running it dies on me right away. PLEASE HELP!!! im running out of ideas.

P.S. i am getting spark on both plugs and they're new, i also thought i flooded the engine (probably) so i put it in gear and cranked the motor by head a few times to make sure it wasn't flooded to no avail.

[wildbill]

ok so as i said the right float was maybe a 1cm off from where the float bowls meet the gasket, the left carb is like 3cm above the gasket. Could the crazy offset in float height cause my bike to not crank over??? i mean i set the carbs maybe 3-4 months ago and all of a sudden within the span of a day or so the left float goes out of whack like that, can that happen so drastically??

[beRto]

ok so as i said the right float was maybe a 1cm off from where the float bowls meet the gasket, the left carb is like 3cm above the gasket. Could the crazy offset in float height cause my bike to not crank over??? i mean i set the carbs maybe 3-4 months ago and all of a sudden within the span of a day or so the left float goes out of whack like that, can that happen so drastically??

You are way off on both carbs. I think that resetting the float heights should definitely be your next task here. The float heights help to govern the air:fuel mixture, so if the floats are too high, the mixture will be too rich, and the bike will not run well.

The Suzuki float height spec says +/- 1 mm. So at +1 cm, you are at 10X the max spec value!
http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/FloatHeight

Did you check the float height with Kerry's U-tube method?
http://www.bbburma.net/FloatHeight.htm

[wildbill]

i meant mm, i did the u-tube method and the left one was def off but the right carb was just under. My only hope is after i set the carbs the bike will run again and its not another underlying problem. I just cant imagine how a carb can get so out of sink in the matter of days. I pray that once i jump the bike it will run, wish me luck.

[beRto]

i meant mm, i did the u-tube method and the left one was def off but the right carb was just under. My only hope is after i set the carbs the bike will run again and its not another underlying problem. I just cant imagine how a carb can get so out of sink in the matter of days. I pray that once i jump the bike it will run, wish me luck.

Phew!  "mm" makes a lot more sense (and makes me less panicked )

A float height over by 3 mm is out of spec, but I don't think it's bad enough to give the problems you've described.

Is the air filter in good condition? Are you sure you didn't fill with diesel by accident? Is the inside of the tank rusty (i.e. clogged carbs), or have water in the bottom?

You say the bike won't turn over on its own? What happens when you try? No clicks, whining, etc.? If I understood you correctly, the bike will start and run (briefly) only if jumped or bump started?

[wildbill]

yeah bump starting it allowed it to run for afew sec, when i try to jump it it makes the normal startup sound but doesnt fire to start the engine, the starter motor sounds fine as it normally does. the tank is about half full but there is some rust in the tank, ive been riding the bike now for 2 years and this is the first  time its giving me this type of problem. the lunchbox on it is only afew months old and the gas is maybe a week old.

[wildbill]

Its got compression in both cyclinders, spark on both plugs. At this point im gonna clean the fuel lines, the carb, make sure the petcocks not clogged. Set float height again and pray.

[commuterdude]

Are you getting any drainage of fuel from your airbox vent tube?  Is there any fuel in your oil?  (Level will be way high and oil will be very thin like water).  I ask this as I had a float valve stick open and fuel flooded my carbs spilling over into the airbox and engine.  The bike tried to start but just couldn't run.....battery went dead from me cranking.   I changed the oil to get the gas out of the motor, and the bike ran like new again.   Just a thought.

[wildbill]

Cool, when i get a chance to do the carbs i will move onto draining the oil. Im thinking i had a stuck float too and im pretty sure it wont crank over because the engine is flooded like a beast probably. I dont see any gas spilling out from the drain hose.. actually i think the drain hose is clogged b/c the gas cap has what looks like water or gas at the top.. i think water but will have to check.

[scratch]

Did you set your idle?  What rpm does your bike idle at?

Carb floatbowl breather tube clogged (if you have one, otherwise inspect the upper t-fitting to see if it's clogged)?

Carbs vacuum synchronized?

When was your last valve adjustment?