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stalling when rolling on the throttle (carbed 900)?

Started by junior varsity, March 04, 2010, 10:20:33 AM

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junior varsity

March 04, 2010, 10:20:33 AM Last Edit: March 16, 2010, 01:21:13 PM by ato memphis
So after I tidied up my wiring a bit installing a vizi-tec taillight module, i fired the bike up. Things were going well... Got it up to idle, let it warm up, revved it up and down to 5 or 6k a few times and everything seemed well.

While it was idling, i was checking all my lights and discovered I had forgotten to plug in the front brake switch. no big deal. Plugged it in, went to rev again, and in doing so, it sputtered as I got to about 3k and now it'll die when i try to rev it past there.

Stock mikuni carbs, seems to idle fairly well still. Smell of gas after it dies.

I haven't tinkered with the carb settings any and have left the ignitech with same profile as before (and it was working fine, though not yet dyno tuned).

I don't know much about carbs. I get the principles behind it, but have never tinkered with a set before. From my reading, I am not really sure which problem I have, but it seems like it could be a stuck float?  I'm not sure while it will come to idle right now though and die as i roll on the gas.

Thoughts?  I need to fix the carbs, can't convert to FCR's until the next winter.

Anybody in DFW want to help me fix this over some beer? I'll provide beer for efforts, and pizza for success.

ducpainter

#1
March 04, 2010, 11:06:28 AM
has the bike been sitting for more than a couple of weeks?
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#2
March 04, 2010, 11:08:22 AM
just about 3 weeks (not quite 3).  rode it for quite a long time on a weekend in the middle of February.

I pulled the airfilter to inspect and clean it, wiped out some grime from the bottom of the airbox by the drain hose and made sure no dead bugs had made there way down in there.  put everything back together, and it started right up on about the 2nd or 3rd push of the starter with the choke engaged.

ducpainter

#3
March 04, 2010, 11:18:59 AM
Quote from: ato memphis on March 04, 2010, 11:08:22 AM
just about 3 weeks (not quite 3).  rode it for quite a long time on a weekend in the middle of February.

I pulled the airfilter to inspect and clean it, wiped out some grime from the bottom of the airbox by the drain hose and made sure no dead bugs had made there way down in there.  put everything back together, and it started right up on about the 2nd or 3rd push of the starter with the choke engaged.
Is there ethanol fuel in the tank?
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#4
March 04, 2010, 12:21:05 PM
no more than the normal Texas amount. I put 93 in recently from Shell.

Interestingly, I let it sit for awhile, and when i fired it back up, no problems... Idled fine (just like before) and would rev up and down pleasantly through the rev range. Sounded great...



...Until it warmed up more.. 10m or so, and it would stall as i gave the throttle even a little bit of a twist...

ducpainter

#5
March 04, 2010, 12:24:49 PM
Quote from: ato memphis on March 04, 2010, 12:21:05 PM
no more than the normal Texas amount. I put 93 in recently from Shell.

Interestingly, I let it sit for awhile, and when i fired it back up, no problems... Idled fine (just like before) and would rev up and down pleasantly through the rev range. Sounded great...



...Until it warmed up more.. 10m or so, and it would stall as i gave the throttle even a little bit of a twist...
I think you have a fuel issue. I could be wrong. I have had all kinds of issues with my track bike after sitting for short (2 week) periods.

For S&Gs drain a float bowl and see what you get.

"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#6
March 04, 2010, 12:30:30 PM
ok. is this symptomatic of a stuck float?

(not that i have enough experience to rip carbs apart in a flash, but I can find some free time)

ducpainter

#7
March 04, 2010, 12:32:40 PM
Quote from: ato memphis on March 04, 2010, 12:30:30 PM
ok. is this symptomatic of a stuck float?

(not that i have enough experience to rip carbs apart in a flash, but I can find some free time)
I think if a float was stuck open you'd have fuel spilling out the bowl vent or running into a manifold.

If you suspect a stuck float be sure to shut off the fuel.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#8
March 04, 2010, 12:33:55 PM
i don't really suspect that, I think its odd that it fires up and idles normally... and even revs fine, only to misbehave once it comes up to temp.

svr

#9
March 04, 2010, 12:59:35 PM
hmm, maybe fuel filter or kinked line?  sits for a while has time to fill float bowl, but once it's dry can't supply fuel fast enough to keep up with demand?    just thought i'd guess since i'm dealing with my own fuel issue now.
steven

ducpainter

#10
March 04, 2010, 01:22:19 PM
Quote from: svr on March 04, 2010, 12:59:35 PM
hmm, maybe fuel filter or kinked line?  sits for a while has time to fill float bowl, but once it's dry can't supply fuel fast enough to keep up with demand?    just thought i'd guess since i'm dealing with my own fuel issue now.
Not a bad thought.

Particularly when you consider the bike was tweaked here and there.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#11
March 04, 2010, 01:25:08 PM
I'll check the lines. We're thinking a kink that allows some fuel to flow (enough for idle) but not enough to fill bowls, thus killing it when i open up the throttle after its been running for a bit?

ducpainter

#12
March 04, 2010, 01:28:05 PM
Quote from: ato memphis on March 04, 2010, 01:25:08 PM
I'll check the lines. We're thinking a kink that allows some fuel to flow (enough for idle) but not enough to fill bowls, thus killing it when i open up the throttle after its been running for a bit?
Yup....
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


junior varsity

#13
March 04, 2010, 02:14:51 PM
Checked all the lines. All the fuel lines have some freedom of movement, and aren't pinched.. Definitely no kinks.

Fuel filter is new as of middle of last summer, not very many miles on it sense then (under 1,000mi).

When its cool, the idle and rev feel really really good. Smooth throttle response. After more than 10m of idling though, temps got up over 100c and it went to pot. Roll the throttle and it sputters a bit, back off the throttle and I'm back to idling... rev a bit more throttle and it dies.

I've got a quick turn throttle on the bike, but there's been no change since last time I rode to the cables and such (everything looks normal - throttle and choke); choke seems to work quite fine, just like normal when the bike is cold.

ducpainter

#14
March 04, 2010, 02:28:07 PM
have you drained a float bowl?
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


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