bike running lean, hard starting

[d16soda]

Hey guys, posted a few times about this before. My bike is very hard to start cold. Just recently did a valve adjustment a few days ago, oil changed, good battery, new plugs and wires. The reason i think its running lean is because it wont start unelss i cover the intake with rags and choke fully on. then i release the choke completely and leave one hold on the airbox plugged and let it warm up. if i dont restrict airflow in the airbox the bike dies.

Now the carbs have been cleaned but i was wondering about where the choke ports into the bowls. I dont remember cleaning that and i was wondering what i should do. I just dont think the choke is working right because it will kill the engine. Why is the bike running lean? The idle/air mixture screws havent even been drilled out from the factory. By the way it is a 2005 Ninja ex250 with roughly 3,000 miles.

[n4mwd]

Originally Posted by d16soda

Hey guys, posted a few times about this before. My bike is very hard to start cold. Just recently did a valve adjustment a few days ago, oil changed, good battery, new plugs and wires. The reason i think its running lean is because it wont start unelss i cover the intake with rags and choke fully on. then i release the choke completely and leave one hold on the airbox plugged and let it warm up. if i dont restrict airflow in the airbox the bike dies.

Now the carbs have been cleaned but i was wondering about where the choke ports into the bowls. I dont remember cleaning that and i was wondering what i should do. I just dont think the choke is working right because it will kill the engine. Why is the bike running lean? The idle/air mixture screws havent even been drilled out from the factory. By the way it is a 2005 Ninja ex250 with roughly 3,000 miles.

If the engine runs and idles fine when its warm, then its probably not the carbs. They don't unplug themselves just because its warm.

If your valves are set too tight, it will be hard starting. I just set mine on the wide side of the allowed tolerance and it wont start cold WITH the choke, but starts right up without it.

I would leave the mixture screws alone as they only affect the idle mixture when not choked.

[choneofakind]

I'm not surprised that your bike dies on you when you turn off the choke immediately when you start it up. Give it 1/2-3/4 choke, and start it. Or start cranking it without choke, and immediately start giving it choke until it starts. Usually when it goes from that threshold of lean to rich, it will fire. Then keep the choke where you left it so it will stay running. Don't turn the choke all the way off the second it starts just because it started up.

http://faq.ninja250.org/wiki/What_is..._at_startup%3F

also, if you're having issues getting it to stay running while it warms up, try starting it and moving right away while keeping the rpm's low. It warms up much quicker when it's under load and at higher rpms than 1400. After about a mile of low-rpm riding, ease the choke off and see how it idles. Then just take it easy on the rpm's until your temp gauge is where it should be.

[n4mwd]

Originally Posted by d16soda

... new plugs and wires....

After re-reading your post, I'm wondering how you did that....

[dubojr1]

Was it hard starting prior to the valve adjustment?

[d16soda]

not sure what you are asking when you ask how i did plugs and wires.

yes it was starting hard before the valve adjustment. I did all of them on the looser end of the adjustment range. Before the adjustment, all of the valves were too tight to even put a feeler gauge in between the lobe and the rocker arm.

Sometimes if the temperature isnt too cool, my bike will start cold with the choke. only full choke. I have to put it on full choke, let it crank, take off the choke immediately and blip the throttle or bring the idle up for it to stay running.

when the bike is started cold, any amount of choke will kill the engine.

Could the little choke port be clogged or something by chance? i noticed it next to the jets when i removed the bowls, but I dont remember it being clogged visibly.

it is also a lot easier to start and it will idle higher if i partially cover the airbox with a rag.

[dubojr1]

Originally Posted by d16soda

not sure what you are asking when you ask how i did plugs and wires.

I think he asked because I believe our plug wires are attached to the coils so without changing the coils you can't change the wires.


Overall sounds to me like the engine is starving for fuel. I think I would pull the carbs and verify again that all passage ways and jets are clear.

[d16soda]

Originally Posted by dubojr1

I think he asked because I believe our plug wires are attached to the coils so without changing the coils you can't change the wires.


Overall sounds to me like the engine is starving for fuel. I think I would pull the carbs and verify again that all passage ways and jets are clear.

Haha, yes, the coils were replaced. sorry for the ill-wording.

I understand that its starved for fuel, but can't that be cured by changing the idle/air mixture screws? I have to pull the carbs off to drill the screw caps out anyways so i will just double check everything. what a pain in the a**!!

[dubojr1]

Have you shimmed your needles? That would be a great time to do this as well!

[n4mwd]

Originally Posted by d16soda

not sure what you are asking when you ask how i did plugs and wires.

yes it was starting hard before the valve adjustment. I did all of them on the looser end of the adjustment range. Before the adjustment, all of the valves were too tight to even put a feeler gauge in between the lobe and the rocker arm.

Sometimes if the temperature isnt too cool, my bike will start cold with the choke. only full choke. I have to put it on full choke, let it crank, take off the choke immediately and blip the throttle or bring the idle up for it to stay running.

when the bike is started cold, any amount of choke will kill the engine.

Could the little choke port be clogged or something by chance? i noticed it next to the jets when i removed the bowls, but I dont remember it being clogged visibly.

it is also a lot easier to start and it will idle higher if i partially cover the airbox with a rag.

I have never seen a Ninja with replaceable spark plug wires. The only kind I have seen are integrated into the coils. You said you replaced them so I'm wondering how you did that without damaging them.

When you did the valves, are you positive that you used metric feeler gauges? Also metric feelers for the spark plug gapping?

I trust the new plugs are NGK CR8HSA and not champions or CR7 plugs or anything else.

If it runs fine when its warm, then its not the carbs. Are you sure the choke cable is hooked up properly?

[dubojr1]

Wait... where does it say it runs good warmed up?

PJ: How does the bike run once warmed?

[d16soda]

runs perfect warmed up. its my daily driver. no missing, no poppy of the exhaust.

[dubojr1]

I'm thinking valves then. Are you confident you got them right?

Have a read of this. Sound similar?

http://www.ninjette.org/forums/showthread.php?t=43675

[dubojr1]

Double check that choke cable though. Could be an easy fix!

[d16soda]

valves were done to that guide. i used metric gauges.
just took the choke cable off and put it back. it is on right for sure.

[dubojr1]

I don't know man. I'd do a compression and leak down test to test those valve. Seems more often than not that tight valves will cause hard cold starts.

[d16soda]

well they are loose for sure. the exhaust are loose enough to tap a little too.

[CmichRider]

What about the idle mixture screws....I know that they are turned lean from the factory, maybe turning them out will help?

[dubojr1]

Any luck with this PJ?

[d16soda]

hey sorry, been really busy.

havent had a chance to do anything yet, but im going to drill out the mixture screws and enrich the fuel a bit see how it goes. will post results. thanks thus far.