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Hello,
I have a 2008 Kawasaki Ninja 500R. I bought it lightly used from a guy on Facebook who was selling it for really cheap. He said it sat for a season with fresh gas and a stabilizer. So far, I've completed an oil and oil filter change, replaced the spark plugs, flushed and replaced the coolant, tuned my throttle cables, oiled and lubed all the cables, and cleaned out my carbs, including the main/pilot jets with see-through holes, following all those instructions on the wiki. After that I charged the battery. I didn't do all of this in one go btw, I tried starting the bike after each maintenance step to no avail.

Basically the bike only runs on full choke, and dies after idling at 3k rpm. It fluctuates between <1k rpm and ~3k rpm with no throttle, then just dies... With throttle it lugs on and runs pretty decent. I can turn the choke off after a few minutes and still have it run decently for another minute or two but then it just dies (usually after hitting 1.5 to 2k rpm for a bit) A quick search on this forum led me to a post that told me it could be a fuel restriction or a gas cap venting issue, which I eliminated by just opening the gas cap and having it run. Same issue...

So fuel restriction... How can I DIY that? Petcock rebuild, vacuum diaphragm repair? Or could it be something a bit more sinister?

Any help appreciated! Thank you
 

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hi. I would say it's 90% a carb/fuel issue. it was bought cheap after being stood so one can't be 100% sure as one never really knows what it ran like or the reason it was left stood.
make sure you have fresh fuel. and enough in the tank. pull it off the bike stand it somewhere safe. then while it's off put a container under the petcock. turn to on see if any fuel leaks (it shouldn't) then add a tube to the vac line of the petcock and gently suck on the pipe. fuel should flow now from the petcock then when you release the vac it should stop again.
this is just to prove the petcock is working. next look at the carbs are all the pipes intact/secure do you have the PAIR system fitted. if not is the little bung on the right carb in place and secure. note the petcock vac line goes on the left carb.

if all this is correct and working you can discount petcock and fuel tank being the issue.
now move to the carbs I'm afraid there is more to cleaning these than checking the jets. all the tiny pathways have to be clear. the rubber diaphragms in good condition and seated correctly. the carbs have to be balanced. and float heights wet checked for correct level. if this was not done you will have to re do them. there is more you can check but that is enough for now. I think....
 

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THE CARB VENT will create the condition you describe, if it is blocked it will prevent the flow of fuel into the carbs. remove it. Its the yellow hose connected to the forward rail between the carbs

FOG
 

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Discussion Starter · #4 ·
THE CARB VENT will create the condition you describe, if it is blocked it will prevent the flow of fuel into the carbs. remove it. Its the yellow hose connected to the forward rail between the carbs

FOG
This did it! I removed the line and it started up first try, no choke. Was at a low idle speed so I adjusted the idle knob under the carbs and up it went to 1250+-50. Have had it running for 5 minutes now, without an issue! Thanks Fog :D
 

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Discussion Starter · #5 ·
hi. I would say it's 90% a carb/fuel issue. it was bought cheap after being stood so one can't be 100% sure as one never really knows what it ran like or the reason it was left stood.
make sure you have fresh fuel. and enough in the tank. pull it off the bike stand it somewhere safe. then while it's off put a container under the petcock. turn to on see if any fuel leaks (it shouldn't) then add a tube to the vac line of the petcock and gently suck on the pipe. fuel should flow now from the petcock then when you release the vac it should stop again.
this is just to prove the petcock is working. next look at the carbs are all the pipes intact/secure do you have the PAIR system fitted. if not is the little bung on the right carb in place and secure. note the petcock vac line goes on the left carb.

if all this is correct and working you can discount petcock and fuel tank being the issue.
now move to the carbs I'm afraid there is more to cleaning these than checking the jets. all the tiny pathways have to be clear. the rubber diaphragms in good condition and seated correctly. the carbs have to be balanced. and float heights wet checked for correct level. if this was not done you will have to re do them. there is more you can check but that is enough for now. I think....
I didn't need to do this as fog's solution worked below but I'm curious about the petcock. Is this specific petcock prone to issues? Or petcocks in general?
 

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no idea. about other types I never used them. I get a bike with a vac operated petcock it gets removed. ASAP I use nothing but manual ones. since being lazy about 20 years ago forgetting to turn one off while parked on a weekend at the coast, the bike had no fuel left in the tank it was all in the crankcase.
they do seem problematic though if the number of threads is anything to go by. apart from battery and carb issues seems to be number 3 on the list. so always worth checking it's operation, before pulling the carbs.
glad Fog's idea worked it was the next thing on my list to check.
 

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The factory vac activated petcock is pretty reliable.
 

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note to all if you still have that stupid vent hose please remove it and throw in in the trash

FOG
 

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The factory vac activated petcock is pretty reliable.
that is very much the description of the whole bike bpe. yet the forum of is full of threads about bikes that are not (reliable), the issue is not the petcock itself but the riders complacency. because it's vac operated it gets used as a automatic shut off valve. which is fine until it does fail. the answer would be to shut it off everytime you park the bike.
but if your going to do that why would you need a vac operated one in the first place. seems logical to me.

Done and done. Why is it even there if it can prevent fuel flow? The hose specifically I mean
because it's the vent pipe. while it can be problematic if blocked or mis routed allowing wind to disrupt the float levels.
it must have a purpose or Kawasaki would not have fitted it.
 

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it must have a purpose or Kawasaki would not have fitted it.
SAFETY is its purpose. Theoretically, the vent hose, in the event of a laydown, vents spilling fuel from full bowls away from the hot engine.
 

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Well as one who has inverted several EXs over a 12 year run as a racer. I have never seen any evidence of fuel escaping the un covered vent.
also there was/is no race regulation covering that vent.
It must have been designed by the Lawyers.
 

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the forum of is full of threads about bikes that are not (reliable),
No part on our bikes or any other bike is 100% full proof. We may have a couple of hundred threads on OEM petcocks going bad. None of the 10's of thousands of OEM petcocks that have gone the distance get a thread. IMO the factory petcock is more reliable than the majority of all the aftermarket petcocks, and at the very least as reliable as the others. FYI even a petcock turned to the off position can fail and leak.

I stand by my statement.
I have never seen any evidence of fuel escaping the un covered vent.
We have seen evidence of fuel escaping the uncovered vent due to grossly high fuel levels in the carbs. I have no idea what these guys are riding through that would clog the vent tube. But I think another valid fix would be to remove the tube and blow it out then replace. It's not rocket science.
 
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No part on our bikes or any other bike is 100% full proof. We may have a couple of hundred threads on OEM petcocks going bad. None of the 10's of thousands of OEM petcocks that have gone the distance get a thread. IMO the factory petcock is more reliable than the majority of all the aftermarket petcocks, and at the very least as reliable as the others. FYI even a petcock turned to the off position can fail and leak.
the issue is not the petcock itself but the riders complacency. because it's vac operated it gets used as a
automatic shut off valve. which is fine until it does fail. the answer would be to shut it off every time you park the bike.
but if your going to do that why would you need a vac operated one in the first place. seems logical to me.
I think you missed the point I was making. I have had vac petcocks go bad in the past. but in the 20years since using a manual one and the numerous bikes that never had one. not once has a manual petcock failed. (of course I would never dream of using cheap Chinese knock off ones) but that is not the issue.
 

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^ No I got your point, just don't agree.
 

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^ No I got your point, just don't agree.
no surprises there. different perspective different opinion. no one could convince me to put a £160 (with tax) OEM petcock on £300 bike when it's main function is somewhat redundant by it's use. plus given the reason for changing it was the old units failure.
 

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^ Looks like your bikes are cheaper, but the petcocks are more expensive. 😮
 

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yeah you got that right. the reason is down to history. but that is a topic for another time. suffice to say if you do have a GPZ500s (EX500). it's because it was dirt cheap and nobody else wanted it.
 
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