I purchased my first bike about a month ago. 1986 ninja 250, the bike only has 6300 miles on it currently. It is extremely clean, the spark plugs are burning correctly, gapped correctly, the carbs are spotless. The problem comes when the bike sits around for awhile and cools down, it will not start using the starter. The only way to get the bike started when it is cold is to push start it. It might take a couple of tries, but it always works. When I bought the bike it started fien when cold. I have tried starting it with choke, no choke, throttle all combinations. Other then this issue the bike runs flawlessly. When it is warm it starts using the starter without question. When I got out of work yesturday I had the hardest time yet starting it. It came to the point that I was in gear pushing with my legs trying to get it fired up. When pushing I could hear the engine fire but not "Catch", but it eventually did, not after I broke a sweat. Any opinions are greatly appreciated, I am just plain stumped.[:@]

 

Get a new battery then go from there.

Welcome to KF.

 

Agree^. Once the bike is "warmed-up" the (dead) battery gets just enough charge to re-start your (now lubricated) engine.
Follow the directions for charging your new battery. Don't get in a hurry by using a 200amp starting charge; get out the 1 amp trickle charger after you tap the newly-filled battery a few times. This gets the air bubbles off of the lead plates, which translates to no "dead spots" in your cells. Charge thenew battery for about5-7 hours, and make sure you allow for overflow with a "splat mat."

 

I was getting 12.6 volts with the volt meter from the battery. May the battery not have enough strength for cranking?

 

^ it is cranking over fine, this morning even push starting I couldnt get it started. May I need Hotter plugs?

 

If the engine is "cranking over fine" when it's cold, then it's fuelor spark. If it runs OK when you actually get it going, it sounds like it may be a choke problem. What color deposit is on your plugs after you run the engine? If you pull the plugs and put a trickle of gas in each cylinder before you try to start it when cold, will it fire? (The ol' 2-stroke dirt bike trick!)
I wouldn't use ether (starting fluid) to get it going; can cause problems you don't want...
Have you checked each component of the ignition system to be sure it's getting juice where it should (and the proper amount?)Do you get spark at the plugs?

 

The bike runs great once I get it going. The plugs have a nice even brown color between each of the two cylinders. I am getting spark from the plugs while cranking. I have already visually checked that the choke lever actually does move something on the carb. I know the choke works, because once I get the bike going the bike WILL idle high on its own. Thanks for your help trying to trouble shoot this. I have been working with automotive engines for awhile, and I am just stumped.

 

I would stay with the stock or oem plugs for now. It sounds like the low speed circuit of the carbs are causing you fits. When you cleaned them, did you resync the carbs?

 

what is the are scroo set at? on each carb what piolet jets are you running