Rough Idle

[BartZerv579]

Hey all,

I am completely lost here and could really use some helpful insight.

I have a 1995 Ninja 250, and when I bought it, it had a rough idle. It only idles over 3k RPM, and below that, it just sort of dies out. I assumed it was just the carbs that were a little gunked up, so after I bought it I went through the carbs and that didn't seem to help. I went through them a second time, blowing carb cleaner and cleaning out all jets and any places that could possibly have gunk in them. This still didnt seem to work. I did some research and read that this might be tight valves, so I went through and adjusted the valve clearance on all the intake and exhaust valves. I put the radiator and the tank back on and started her up, and it seemed like it wanted to idle better at about 2k or so, but it sounded loud and there was a sort of clunking sound coming from the engine. Im at a loss here! Any suggestions or diagnoses are greatly appreciated! I just dont know what else it could possibly be, or what I could do.

[ieathonda]

Try adjusting the mixture screws. There is a write up on the ninja wiki: http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

[BartZerv579]

Originally Posted by ieathonda

Try adjusting the mixture screws. There is a write up on the ninja wiki: http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

I've heard about doing that before! I'm about to go through and recheck the clearances again, and if that doesn't work I'll for sure give the mixture screws a try.

Thanks!

[ieathonda]

Make sure to measure the valve clearances before and after your tighten the rocker arm nuts down. They mo e a bit after adjustment. I had to check a few times over to be sure myself.

[Ghostt]

You need to do a through and meticulous carburetor cleaning, servicing, and adjusting, check for vacuum leaks and then possibly a value adjustment, but you need to be 100% sure the carburetors are right, otherwise your chasing your tail so to speak.


My quick how-to on idle adjustment

Your initial setting should be 3 full turns out from the bottom, remember just slightly tighten them, don't go all Conan on them, due to they are brass and the tip can be damaged by over- tightening.



Then warm it up, slowly turn 1 side pilot screw in until the rpms drop, then back out till RPM's peak (and no further)* Twist throttle...see how it reacts...tweak to taste.
Repeat on other side... test ride. You're looking for best throttle response and transition from just cracked to 1/4 throttle opening or so.*

Thats a quickie, 10 cent tutorial on setting pilot screws.**