2007 won't idle. Vacuum leak or something else?

[cookiebug79]

Hey everybody!

I went to start my pre-gen ninja 250 and it won't idle. It has only been sitting about 3 weeks so I don't think it's clogged carbs. I can start it with the choke on. When it warms up and I start to reduce the amount of choke, the idle starts to surge. If I take the choke completely off it dies. If I give it throttle with the choke on it dies. It was running fine when I last rode it.

I figured it was a vacuum leak. I sprayed carb cleaner on all of external areas that could be leaking and listened for the idle to even out for a bit. The only time that worked was when I sprayed it in the air cleaner. The air cleaner screen is clean. Since nothing obvious was coming up, I started disassembling. I completely removed the carbs and ended up cleaning/rebuilding them. But as I suspected, they were spotless. All of the hoses seemed ok. I re-assembled everything and put it all back together. No surprise, the issue is still there. Here's a video of how it's running.

I would appreciate any recommendations for root cause and next steps. I was hoping to take it to a track day on Saturday.

http://youtu.be/4syU_BwHyFU

[tc.young]

If nothings changed since the last time you rode it and it was running fine then, I wouldd suspect the carbs. One quick thing qyou could do would be drain the carbs and then try and run it. Some fresher gas may help but who knows. Or keep running it with the choke on and play with the throttle and hope something clears up.

[Motofool]

Those high rpms' can hurt a cold engine !!!
Continuous start ups don't solve a problem but create a new one: dead battery.

It seems that you have missed some little passages that belong to the idle circuit.

After sitting for a month, a friend had the same exact problem and called me.

I always believed that clogs produced by gasoline upon evaporation can be dissolved by gasoline plus heat.

So, using only choke, I made the idle stable at around 2K rpm and gently started moving the bike and took it to the freeway for a spirited ride (kept choke open all the way).

Ten miles later, and every time he started it later in that week, the bike was idling as new.

[jkv45]

I'd drain the fuel and refill with fresh before going much further.

Condensation can form quickly if the temps are changing and the tank is low.

Always start your troubleshooting with known good fuel. It one of the easiest problems to fix and nothing else will make it run right if the fuel is bad.

Use 87 without Ethanol if you can.

[crazymadbastard]

Make sure your battery is fully charged also.

[cookiebug79]

Yeah, the battery is starting to get weak


After I pulled/cleaned/re-adjusted the carbs last night, I'm positive the "let it warm up and ride it" isn't an option. I've employed that a lot in the last 12 years and currently this is behaving differently. There's something else going on. My theory is that it's running rich. After it warms up a little, if I give it throttle it kills it (too much fuel). If I lower the choke more than half way, it kills it (not getting enough air). I can't get it to idle consistently. If there's a vacuum leak, and it's running rich, then that makes sense... No it doesn't. 'Cause a vacuum leak would allow it to run without the choke because it would be adding air. So there's too much air and it's running lean. Having it die when adding throttle means too much fuel and running rich? Which then points to a clogged air passage somewhere... And the surging is the diaphragms adjusting to the vacuum needs...


&*^#$*(@#^$@*!!!!

[Motofool]

Originally Posted by cookiebug79

.........My theory is that it's running rich. After it warms up a little, if I give it throttle it kills it (too much fuel). If I lower the choke more than half way, it kills it (not getting enough air)............

Sorry to say that your theory is incorrect: the mix is excessively lean as soon as the butterfly valves start to open.

Yes, you could roll away with the choke fully open and opening the throttle very little.

[alex.s]

the answer is obvious.

you suck at cleaning carbs!

open them up again. remove each jet. spray carb cleaner in the jet, then twist a tooth pick through the jet. soak the jet in carb cleaner then scrape the inside with another tooth pick. dont use metal it will scratch things up. spray carb cleaner through the internal passages in the carbs and if you can, soak them or even use one of those fancy ultrasonic cleaners. i've known many people to "clean their carbs spotless" and yet still have issues until i go and pull crap out of their jets... "but it was clean!"... not clean enough i guess. maybe dirty fuel filter is fouling it up again... dirty gas tank? rusty gas tank? **** in the petcock floating down stream? you have replaced the gas in it right? there could be lots of different reasons its getting dirty again or remaining dirty... but what you describe is a clogged main jet.

[cookiebug79]

Originally Posted by alex.s

... i've known many people to "clean their carbs spotless" and yet still have issues until i go and pull crap out of their jets...

This statement amuses me...


I *heart* internet uncredit from anonymity.


Love ya, Alex!

[jkv45]

Originally Posted by cookiebug79

Hey everybody!

I went to start my pre-gen ninja 250 and it won't idle. It has only been sitting about 3 weeks so I don't think it's clogged carbs. I can start it with the choke on. When it warms up and I start to reduce the amount of choke, the idle starts to surge. If I take the choke completely off it dies. If I give it throttle with the choke on it dies. It was running fine when I last rode it.

If there's an issue with the carb, this description would suggest the pilot jets are clogged.

I'd first replace the fuel, drain the float bowls, then start it and keep it running for a few minutes, then adjust the idle speed screw to see if it will idle without the choke. If it idles poorly, make some adjustments to the idle mixture screws (turn them out most likely).

If it won't idle by doing those things I would say the pilot jets should be removed and carefully cleaned.

[j98sprint]

Alex is right. You're not cleaning the carbs correctly. If you follow the instructions for carb cleaning and proper set-up, meaning correct float height and sync, that are on the "How-To" page of that other Ninja 250 web site your problems will go away.

j98sprint

[cookiebug79]

Originally Posted by Motofool

Sorry to say that your theory is incorrect: the mix is excessively lean as soon as the butterfly valves start to open.

Yes, you could roll away with the choke fully open and opening the throttle very little.

Yeah, which I think I deduced through later on in that rant.


I totally get and have used the theory you are speaking of - the get it rolling with the choke on, ride it with load and higher RPM, get it good and warm and it clears itself up. Something is too effed up in the fuel system to allow it to move under load, even when it's revving above 5K with the choke fully on.

I am going to try to replace the gas in the tank. That was a good call. I've got some happy Nevada gas that doesn't have all the California emissions/ethanol junk in it. Except right now all of my gas tanks are full. D'oh!

[jkv45]

Originally Posted by cookiebug79

I am going to try to replace the gas in the tank. That was a good call. I've got some happy Nevada gas that doesn't have all the California emissions/ethanol junk in it. Except right now all of my gas tanks are full. D'oh!

Just make sure it's fresh.

87 without Ethanol is always the best, but not everyone can get it unfortunately.

[cookiebug79]

Originally Posted by jkv45

If there's an issue with the carb, this description would suggest the pilot jets are clogged.

I'd first replace the fuel, drain the float bowls, then start it and keep it running for a few minutes, then adjust the idle speed screw to see if it will idle without the choke. If it idles poorly, make some adjustments to the idle mixture screws (turn them out most likely).

If it won't idle by doing those things I would say the pilot jets should be removed and carefully cleaned.

Thanks for your feedback. And explaining why the symptoms point to the theories!



By "idle mixture screws" - I'm pulling from my memory - are you referring to the external screw you adjust when you sync the carbs, or the pilot jet screws under the bottom of the carbs?

Thanks.

[Motofool]

Originally Posted by cookiebug79

........Something is too effed up in the fuel system to allow it to move under load, even when it's revving above 5K with the choke fully on........

If you are convinced that you have no way to avoid working in the carbs again, then take a look to this:
Secret Passages

Yes, those are the screws that have been mentioned above.
Actually, they need to be removed for a proper cleaning of the idle or pilot circuits (be gentle with their O-rings).

You don't really need to replace the tank, cleaning it up from debris and some water and adding a good in-line filter will suffice, IMHO.

A decent flow of clean air and gasoline is all the carbs ask for.

[cookiebug79]

Found the culprit! The o-ring in the idle circuit is in multiple pieces...

[cookiebug79]

So, yeah, after work I filled a small spare tank with fresh gas and hooked it in to the carbs and it still ran poorly with the surge. So I loaded it up with all of my track stuff, threw the fairing in the back seat, swung by auto zone for 2 cans of carb cleaner, seafoam, hose clamps, and new vacuum hose. I headed up to Willow Springs and tore the damn thing all apart again. Luckily one of the trackxperience guys had an o-ring kit. He's purring like a kitten, now!

[Motofool]

[fast1075]

I can't help myself. The "choke" isn't a choke. It is an enrichening device. It does not function at all except at idle r very small throttle openings.

[jkv45]

Originally Posted by cookiebug79

Found the culprit! The o-ring in the idle circuit is in multiple pieces...

That will do it!

Glad you found the problem and it was something simple to fix!

[jkv45]

Originally Posted by cookiebug79

By "idle mixture screws" - I'm pulling from my memory - are you referring to the external screw you adjust when you sync the carbs, or the pilot jet screws under the bottom of the carbs?

Thanks.

Just to clarify, though you have it figured out at this point, the idle mixture screws are the ones the are on the bottom of the carbs toward the front. Stock they have caps covering them. I don't think you could remove the caps without removing the carbs, so make sure they get removed if the carbs are off. On the Ninja, turning the idle mixture screws OUT allows more fuel to flow and RICHENS the mixture.

Note that not every idle mixture system operates the same - some are air-bleeds that are opposite (IN is RICHER), so you need to know which system your carbs use.

The screws used for syncing the carbs are on the top, and alter the relationship between the carbs.

[cookiebug79]

Originally Posted by jkv45

Just to clarify, though you have it figured out at this point, the idle mixture screws are the ones the are on the bottom of the carbs toward the front. Stock they have caps covering them. I don't think you could remove the caps without removing the carbs, so make sure they get removed if the carbs are off. On the Ninja, turning the idle mixture screws OUT allows more fuel to flow and RICHENS the mixture.

Note that not every idle mixture system operates the same - some are air-bleeds that are opposite (IN is RICHER), so you need to know which system your carbs use.

The screws used for syncing the carbs are on the top, and alter the relationship between the carbs.

Cool, thanks for the clarification.

[n4mwd]

In the photo of the bad o-ring on the mix screw, where's the washer? There should be a little washer between the spring and o-ring or else the new one will grind down and look just like the old one.

Oh, and there are 6 jets you need to clean when you clean a set of Ninja carbs. Each carb has a choke jet, pilot jet and main jet. The choke jet is often overlooked and AFAIK is not removable. So you just have to use a thin wire or blast it with air or carb cleaner. The main and pilot jets must be removed in order to properly clean them.

[cookiebug79]

Originally Posted by n4mwd

In the photo of the bad o-ring on the mix screw, where's the washer? There should be a little washer between the spring and o-ring or else the new one will grind down and look just like the old one.

Oh, and there are 6 jets you need to clean when you clean a set of Ninja carbs. Each carb has a choke jet, pilot jet and main jet. The choke jet is often overlooked and AFAIK is not removable. So you just have to use a thin wire or blast it with air or carb cleaner. The main and pilot jets must be removed in order to properly clean them.

Good observation! The washer is just not in the picture. I promise, it's there. O-ring, washer, spring, needle valve turned all the way in and then backed out 2 1/2 turns. Got it. It was 11 pm and I was cleaning/re-building my carbs on a table at a race track, so I didn't document everything. I was also pissed that I had to sit there and dig chunks of o-ring out of my idle circuit with a piece of safety wire instead of drinking beer and BSing with the rest of the track staff.

#1stworldproblems