CF650nk Dies while driving or misfires but starts after that normal

[Wald0]

So problem is this. Bike starts good and idle good, driving a while it might start to backfire and refuse to rev without backfiring and lunging forward (loosing power and then suddenly getting power) some times EFI error light comes on with one long and 2 short flashes = ERROR_INJ1(1cylinder injector)_SCG = S.C.G = Short Circuit to Ground.
If i keep rev's high it don't backfire (above 5000rpm) and runs... well fast :)

Today i also notice first time ever that idle went up and down for a while.
never notice this symptom before.

but odd thing is that if it start to do that i just hit kill switch (while driving even) let it roll a bit then hit start and problem goes away?? and bike runs good again.
at least for while, sometimes full day.

second symptom is similar but instead of backfiring while driving it started to die suddenly. just pull clutch and it dies, again starting the bike there is no sign of problems!!


I first thought it was dirty fuel so i did empty gas tank and filled it up fresh fuel. still same thing.. (did not clean filter thinking it would replace bad with good later... )

when i removed tank i notice that after i removed fuel line from fuelpump it was still leaking gasoline.
Is this normal??
When i removed tank on my Yamaha FZ1 it did not let fuel out at all.

[Wald0]

UPDATE: While driving work it started to die more and more.. Fuel level was 2 bars still
decided to stop for refuel and after that it worked again and did not die at all!

Could this just be failing fuel pump? because it did idle ok but if i tried to turn throttle
it died unless i slipped clutch and raised PRM a lot.

[ZMC888]

Could it be bad fuel? Not sure about bad fuel in Vietnam but in China it could cause the problems you're talking about.

[choldy]

Possibly a vacuum issue, next time it dies just open the fuel cap to see if you've got a vacuum forming in the tank, if so check to make sure none of the breather pipes from the tank are kinked or pinched...

[Wald0]

Could it be bad fuel? Not sure about bad fuel in Vietnam but in China it could cause the problems you're talking about.

I was thinking same thing and thats why i did suck old gasoline out from the tank. but it still did it.
but now it has been "behaving" good but again i am approaching that critical fuel level so i will know tomorrow or day after that will it start to die again.

[Wald0]

Possibly a vacuum issue, next time it dies just open the fuel cap to see if you've got a vacuum forming in the tank, if so check to make sure none of the breather pipes from the tank are kinked or pinched...

This could be the case also, but oddly if i don't remember wrong last time when i removed tank one of those vacuum pipes was full of gasoline..?

[Kennon]

breather pipes never fill up with fuel they are there to draft air into the tank when the fuel is being pumped out if its kinked it'll cause a lack of air meaning the pump can still keep pumping but only a very limited amount of fuel would get through, I had a fuel starvation problem with my bike at higher speeds where the suction was strong enough it would run fine but below 8K revs it would stutter allot.

Kennon

[Wald0]

breather pipes never fill up with fuel they are there to draft air into the tank when the fuel is being pumped out if its kinked it'll cause a lack of air meaning the pump can still keep pumping but only a very limited amount of fuel would get through, I had a fuel starvation problem with my bike at higher speeds where the suction was strong enough it would run fine but below 8K revs it would stutter allot.

Kennon

Previous owner must have removed tank and mixed those two hoses under tank. Started to notice that after i wash bike it had lot of water near fuel cap and once i opened it, all water went to tank.
So that is now fixed.
and lately symptoms have disappeared.

[kfteng]

Previous owner must have removed tank and mixed those two hoses under tank. Started to notice that after i wash bike it had lot of water near fuel cap and once i opened it, all water went to tank.
So that is now fixed.
and lately symptoms have disappeared.

Hi Wald0,
Im facing the same problem on my cf650nk.
This issue only happen Initial driving. after the engine warm up, it smooth as silk.
--------------
May i know how do you fix this issue?
Please.

[Wald0]

Hi Wald0,
Im facing the same problem on my cf650nk.
This issue only happen Initial driving. after the engine warm up, it smooth as silk.
--------------
May i know how do you fix this issue?
Please.

Think my problem was water in the tank, so i drained the tank and that was end of it.