fuel starvation :(

Happened again today.

riding and first 10 min is ok.
then i start losing power and when i stop i stall.

stuck it on PRI, waited and started again....
barely got home and it stalled(on PRI) pop open tank....no hissing sound.

i'm going to replace all my hoses i have no clue what it can be.

I used to have crappy clear hoses. They would look fine but they get hard. Once they got a bend in them that was it. Hard clear hose with a bend can restrict fuel. I changed mine to the good stuff - proper black fuel line - from an automotive store. No problems since and I'll never use clear again.
Good luck.
......................................................
Woodstock ON Canada
1980 kz750 E1, 4 into 1 , K&N pods

well they're not hard they're a lil soft but the main thing is that i'm really not sure why my bike just dies. it doesn't die when i ride around the neighborhood between 30-40 mph. but when i do harder accelerating and speeds over 50 it seems that i start to lose power and acceleration then idle will drop and the bike will die. then i pop it to PRI then wait then start it after 30-45 seconds and it starts up and idles ok but rough.

i'm gonna buy hoses, no filter on them and see if the same stuff happens.

Hey tarheel365,
I know you said that the tank didn't hiss when you opened it. Still I'd suggest that you confirm that the gas cap is venting. That's what your symptoms sound like.
KZCSI

well i took apart the cap. i don't know how it is on the kz's but the breather hole isn't just a breather hole....its quite a complex maze of holes, routing, and little rubber valves. i cleaned out the holes and made sure the valves were all ok.

i can also hear a hissing sound near the carbs like a hose was loose but all hoses are attached or capped. i may have a leak in the carb boots.

still...the engine sounds soo nice and as soon as i find that leak i'll be riding again!

Just a suggestion, have you checked your plugs for maybe a lean condition? I was fighting an overheating problem on my KZ900 and it was sounding GREAT. But after I rode it for maybe 10-15 miles and stopped it would quit, start right up again but wouldn't idle without giving it gas... If it's kind of losing power when you're riding faster maybe the floats are set too low?

Good luck.

i just wanna first confirm if i do have an air leak where i think it is. cuz if i have an airleak and stuffed up venting can that reduce the vacuum enough for me to use up available fuel in the bowls but not enough to suck in new fuel from the tank?

well it seems to lose the power after i've accelerated to 50 mph or so a couple of times during a ride. and i can ride around fine around the neighborhood for a while w/o it dying.

Post edited by: tarheel365, at: 2005/10/31 08:43

Hey tarheel365,
I think you're onto something with the air leak. But you should know that the fuel drains by gravity to the float bowls. As a matter of fact that are vented to prevent vacuum from drawing fuel. To check out your intake leak, spray some carb cleaner onto the area you suspect while the bike is running. If the sound or the idle changes you'll know why.
KZCSI

sounds like either your floats need adjusting or you have restricted fuel flow (clogged filter, non venting gas cap, bend in lines)

doh...i guess i don't know how the fuel bowls work.

what is the purpose of the vac petcock if fuel is gravity fed? how does the fuel bowl fill up if its set to ON? i thought the fuel from the fuel bowl goes through the jets and sprayed into the engine.

if my fuel cap was plugged up....riding on PRI after running the bowls down would be fine cuz its gravity fed not vac operated. OR would there be just enough vacuum in the tank(cuz i didn't open the fuel cap) to keep fuel from flowing in PRI.

what is the purpose of the vac petcock if fuel is gravity fed? how does the fuel bowl fill up if its set to ON? i thought the fuel from the fuel bowl goes through the jets and sprayed into the engine.

--- The vacuum petcock allows gas to flow when vacuum actuates a diaphragm that allows gas to pass outwards towards your carb intake. If the carbs are dry, the bowls won't fill until vacuum is created by a running engine. This means you would have to start the bike on Prime. Once the bowls are filled, then gas is drawn into the carburetor venturi by vacuum (it is sucked upwards).



if my fuel cap was plugged up....riding on PRI after running the bowls down would be fine cuz its gravity fed not vac operated. OR would there be just enough vacuum in the tank(cuz i didn't open the fuel cap) to keep fuel from flowing in PRI.

--- If the fuel cap venting is plugged, then gas will not draw from the fuel tank. It won't matter if your petcock is on Prime or ON position.

---

Still not sure what type carburetors you have. Are these CV carburetors and if so, what brand? Do they have external venting? This would be visible as the 1&2 and then the 3&4 carburetors would connect up towards the center of their bodies via a T fitting. If so, this fitting will have a hose attached and it must not be obstructed else the float system will not work. The vents vent the float bowls! If it has an internal venting system, there will be a WIDE passage on the rim of the intake side of the carburetor. If you have pods, it is possible that the pod is covering this type vent. Also, most vented gas caps don't look like they have any venting. They do. If you try running the bike, the bike will run out of gas either slowly or quickly. And have you verified the fuel level was correct in the carb bowls?

phew thank for the info

i have KEIHIN CVK32 carbs.

1-4 are connected by a T connection that goes to the front of the engine. 2-3 are connected by a T that goes to the vac connection of the petcock. i think mine is internal venting.

gas runs out slowly. i think....

i get about 4 miles or so before feeling it. then when i stop the engine dies. i don't open up the tank....i just stick on pri wait a few seconds start it up and go again. and when i get home 2 more miles away....it dies. oh and it was on pri the whole time on the way home.

when i check my fuel level...can i put it on a centerstand? or just stand it straight up?

Post edited by: tarheel365, at: 2005/10/31 13:25
i was just thinking that my problem is most likely from a blocked up gas cap...because even while running on PRI on the way home the engine died as soon as i got home. but i will check fuel level in case i got a lil aggressive w/ pulling off the fuel bowls.:S

Post edited by: tarheel365, at: 2005/10/31 17:37