i am having some issues with an 05 ninja 250 i am working on for a friend.
upon start up it takes quite a while for the bike to warm up. once warm i can ride it. upon acceleration it sputters a little through to around 5k once ubove it seems to run fine. i pegged it out at 95 mph with around 2k more rpm to go but it wouldnt pull any more. i rode it around for about 20 minutes and all of a sudden it has absolutely no power. barely made it home. i had to rev it all the way out in order to get it to move from a dead stop. i pulled the carbs and cleaned them they were pretty clean. the diaphragm on top is another issue. i pulled one out to check if the needles were shimmed and now the damn thing wont go back in. it is so swollen it wont fit.
If at all possible you should 1st isolate if it's a fuel or an electrical problem, then you won't end up wasting a bunch of time doing work you don't need to.
Whenever there's a problem like what you described it's always a good idea to take a look at the spark plugs and see what the carbon residue looks like on the end of the plug. If it's white your possibly lean, if it's black your carb jetting may be too rich. If a plug(s) is soaked in fuel it may be a bad spark plug or issue with spark reaching that plug. If it's got spark then the carb(s) might be dumping too much fuel into the engine, that could be a stuck or misadjusted fuel float or a passage way in the carb being obstructed. If the needle was stuck in an open position that could also cause too much fuel in the combustion chamber and a wet spark plug.
While your checking the plugs make sure you've got spark from each spark plug wire. If you do have spark you can also check the coil(s) fairly easily with an Ohm meter to make sure it's putting out the proper spark - a service manual, the internet, or your local dealer should be able to tell you the correct rating. I had one of the coils go bad on my 1996 GSXR 750, I checked each of them with an Ohm meter (engine off) and it was obvious which one was bad.
A plugged fuel filter (possibly in the tank) can cause fuel starvation problems, also watch out for inline sock/screen filters that can slip down inside the fuel line and be completely unseen from the outside - some bikes have those.
That's some things to check. :thumb:
Also check the emusion tubes. On my son's 04 ninja 250 they are located under both the main and pilot jet's and if they get slightly plugged they will cause the transition issue you discribed. My son's had sat a while before we bought it and it had the same transition issue you discribe,so I ran a staight pin through all the holes in the emulsion tubes and the bike ran great. Oh and 95 is about all your gonna get out of a ninja 250., but man is it fun to ride. All corner speed baby!
FWIW, I was able to get an indicated 90 mph out of my '02 Kawi Super Sherpa. Little 250 4-stroke air-cooled enduro. I am fairly small, though (5'7, 130 lbs), so YMMV.
Quote from: f3racer on June 03, 2010, 11:31:01 AM
i am having some issues with an 05 ninja 250 i am working on for a friend.
the diaphragm on top is another issue. i pulled one out to check if the needles were shimmed and now the damn thing wont go back in. it is so swollen it wont fit.
It will fit. And if you don't get it right, a set of used carbs on Ebay are cheaper than a new diaphragm!