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Ninja 250 Stall when clutch in

Discussion in 'Mechanical & Technical' started by CDoc, Jun 27, 2011.

  1. Issue has evolved from this to bad idle/startup. Most recent info found here:

    Troubleshooting already performed:

    Gas tank is full
    Carbs have been pulled and cleaned
    Idle screw set properly to idle @ 1300 RPM
    Pilot screws set to factory


    Once warmed up, the bike will sometimes stall when the clutch is in completely. It happens almost without fail every time I go down a hill right outside my house. I pull in the clutch, and as I coast down the hill the motor will just fall below 1000 and die. It fires right back up though without any problem and I can go about my business. At this point it's more of a pain in the ass. The problem is almost exclusive to downhill rolls.

    At first I thought this was related to my idle issues as it had a tendency to hang out at 4000 RPM when rev'd, but after cleaning the carbs that's no longer a problem.

    So, clutch related? Some google searches implied that this isn't all too uncommon on these bikes, but I'd like some ideas on where to start with this particular issue.

    Last edited: Jun 29, 2011
  2. UGH, I had the same problem on a bike, and couldn't ever figure it out.

    People kept telling me it had something to do with the vacuum hoses, or hoses from carbs to engine. And I would pull them, tighten everything, clean everything, and test for pressure loss.

    What I think happened, was that too much air was getting in to the engine, through the carbs...

    P.S. Who cleaned the carbs?

  3. RedKat600

    RedKat600 Vintage Screwball Staff Member

    I have an sure your floats are set to the proper level. It sounds like when you are tilted forward, it's getting starved for gas. If the gas in the float bowls is too low, you may be starving your pilot circuit which would cause your symptom. Or, the floats are set too high, and you are flooding your motor.
  4. How do you set float levels? That's one thing I never did.
  5. Sentor I'm almost sure I own your old bike lol. I've found your posts on 250 faq and here both describing the same things I've been dealing with. I was even eyeballing that new 250 of yours :)

    As for the carbs, I pulled and cleaned them. They were in pretty good condition actually, but I also seafoamed the hell out of it in the days prior to pulling the carbs. I think there was some water in the float bowls though. When I drained them it had some gas, but more of a consistency of water.

    Either way it seems to be running better as a result, and now I'm just left with this dumbass problem.

    I had opened the bowls to look at the floats but I didnt really know what to do at that point. They were level with each other, so I just put everything back together and went from there.

    I'll have more time to work on it this afternoon. RedKat may be on to something, so I'll go look for some short and steep hills to test the theory on.
  6. That's probably what was wrong with mine. :(

    Haha, never owned the color of ninja in the profile pic... yet! :)
  7. Pilot air screw is too lean.
  8. Well, it looks like what we have here is a textbook case of over-analysis. I'm glad though, as it gave me a chance to tear apart my bike and get to know it better.

    --It was the damn clutch cable linkage. Too loose on one end, and too tight on the lever.

    I don't know how I didnt catch it before, but the bike would manage to lurch itself forward when shifting into gear from neutral, even with the clutch all the way in. I didnt put two and two together.

    Either way, going for a bit more of a spirited ride to confirm, but I think I got it.

    Thanks for your suggestions!
  9. RedKat600

    RedKat600 Vintage Screwball Staff Member

    That still seems odd that it would stall only when going down hill.....braking with clutch pulled in and barely moving?
  10. As expected, I may have spoken too soon. I'm starting to find that I'm fixing several small problems that are adding up and seeming like one big problem.

    The bike runs amazingly better at the moment, so the cable did make a difference.

    However, it did still stall on me a few times after cruising for at least 5-10 minutes then coming to a stop. Thing just stops turning over. This happened on level ground as well, so I think the slope idea was just a coincidence. As usual though, it does fire right back up and I can take off from the stop.

    I'm not entirely sure where to go next other than to pull open the carbs again and try to locate the pilot air screw (no idea what that is. I thought by way of being a carbureted motor air delivery was pretty straight forward.)
  11. RedKat600

    RedKat600 Vintage Screwball Staff Member

    Pilot air screw adjusts the amount of fuel being mixed in with the air at an idle, like your main needle does at open throttle.

    Check float heights too while you're in there.
  12. Might try turning out the air screw 1/4 to 1/2 turn more.
    Is this a new bike to you or have you had it for a while and the problem
    just started?
  13. Trex - It's a used bike that I've had for about two months, so I expected some of this wouldn't be easy. If nothing else though, great learning experience!

    I pulled the carbs again last night. Not sure how I missed this the first time around, but the mixture screws were out of line. One was all the way in while the other seemed to be at the normal level.


    I set them both back to the proper levels, so we'll see later today how it runs.
  14. Might not be the issue but make sure your tank vent hose isn't kinked. My old EX250 drove me insane with this issue. When I finally figured it out I felt really stupid.
  15. Thanks, I'll check that out too. I'd much rather it be something stupid that I overlooked than something highly complex that involves more time and money
  16. RedKat600

    RedKat600 Vintage Screwball Staff Member

    Nice find! Hopefully you won't have to pull them again and mess with floats. I'd bet this is part of your issue, if no the whole issue.
  17. I hope so too. The good news is now that the idle screw plugs are removed, they can be adjusted while the bike is running. Same goes for the butterfly valves.
  18. Sounds like you are on the right track. Bet you can pull and re-install the
    carbs in a instant now with all your practice.crackup:

    Hope your last find will take care of the problem.
    Keep us posted.
  19. You're right about that. The first time I had the carbs out took me about an hour, and last night took all of 15 minutes!

    As for the problem...:banghead:

    Not making much progress, even after the screw adjustment. I'm losing patience quickly with this thing. Now I'm back to my idle issue where after warming up (getting it to start is quite a battle), it randomly decides that it wants to shoot up to 4k RPMs and hang out for about a minute, and has about a 50% chance of stalling when it comes back down. Giving it some throttle duplicates the effect on demand.

    As far as I can tell, there's only two things left: valve adjustment and carb sync. I'm hesitant about the carb sync though, even though it seems to be the easier of the two. Upon visual inspection, the butterfly valves are perfectly matched when opened and closed. I guess it might just be that sensitive of an operation that +/-1mm can cause this kind of bullshit. I doubt it though.

    Also, I feel like this has got to be vacuum related somehow, but I've traced and tested every hose and nothing is obstructed, cracked or loose. The reason I'm thinking this is because if I pull the hose off the coasting enricher, it puts a real quick end to that high idle at 4000, and with the exception of some sputtering and throttle delay, it idles as it should and doesnt hang out in a particular range after rolling on the throttle.


    This is another reason why I'm not convinced that it's the the carb sync that needs done. As you can see from the picture, the hose I'm talking about comes out after the butterfly valves so it doesn't really have anything to do with their alignment (I could be wrong, which is why I'm posting here to begin with :)

    Anyone else have any ideas? Thank you very much for the feedback so far. I'll update with my next move.

    Update: Running rich? I've got a lovely plume of white smoke coming from my exhaust now. At first I thought it was residual seafoam but it would have been long gone by now. Going to try adjusting the screws again.
    Last edited: Jun 29, 2011
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