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2006 ninja 250r wont get up to speed

1K views 6 replies 4 participants last post by  Sev 
#1 ·
so i bought an 06 ninja 250r and for some reason it wont get past 65 70 at 8 or 9,000 rpm it pulls fine through 1st thru 4th gear and after it seems to lose a lot of power. when i start it and have the choke open it idles at like 3 or 4,000 rpm compression is at like 115 to 120 psi in both cylinders it also doesnt like to idle at 1500 rpm at cold starts it sounds like a knocking at low rpm but goes away at higher rpms. when i adjust the idle screw the rpms go way up or way down with small adjustments its wierd. carbs, valves or piston rings?
 
#2 ·
Try new spark plugs first, then try cleaning the carbs, maybe adding a jet kit while you are in them.

Does it go to redline rpm in neutral? If yes, the clutch plates might be worn.
 
#3 ·
I had an 86 yamaha radian with 4 carbs that were "supposed" to be sinked. i had them rebuilt when i first got it, the jets were more than double the size they were supposed to be and i had the same issues you had before and after the new jets were put in. i would say new plugs for sure they are cheap to replace but i would definitely go with a carb rebuild with stock size jets as long as the bike is stock. people try to make bikes go faster with a quick jetting and usually over kill it. go stock see if it fixes it.
 
#4 ·
So heres an update. The knocking sound is coming from the clutch is goes away when i pull on it which i guess is normal unless it sounds like a hammer pounding on the gearbox but the power loss is still there. I have cleaned the carbs and they really werent even dirty. Changed the spark plugs which hasnt done much. So any more ideas guys?
 
#6 ·
Maybe have someone familiar with this bike listen to the clutch noise- it might be unusual, possibly from the problem.

A jet kit often comes with smaller than stock jet sizes, especially if you have the stock air filter and stock exhaust. The previous owner could have added much bigger jets to try to get more power, and got less power instead from adding too much fuel. Were the original spark plugs all black inside?

This video linked below shows the narrow carb jet holes that usually get clogged, usually causing the engine to not idle, and it can also be one of the narrow tubes (fuel passages) inside the carb that gets clogged, possibly for higher throttle settings, usually where there is a 90-degree turn:
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https://www.youtube.com/watch?v=sYEvwiG_1iU
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Another easy check is carefully feeling the exhaust pipes (not near the beginning where you will get burned, and soon after starting the engine) to see if one is a lot hotter than the other.

You can check the compression for both cylinders.

The factory service manual for your motorcycle has several checklists to look for problems. At some point I would give up and have a mechanic look at it, enough to get an estimate to fix it.
 
#7 ·
The idle adjustment going way up and down with small changes sounds like it might be an air leak after the carbs. The bike not idling without the choke out means the idle jets are plugged, or semi-plugged.

Try new spark plugs first, then try cleaning the carbs, maybe adding a jet kit while you are in them.

Does it go to redline rpm in neutral? If yes, the clutch plates might be worn.
Redline in neutral has nothing to do with the clutch plates.

So heres an update. The knocking sound is coming from the clutch is goes away when i pull on it which i guess is normal unless it sounds like a hammer pounding on the gearbox but the power loss is still there. I have cleaned the carbs and they really werent even dirty. Changed the spark plugs which hasnt done much. So any more ideas guys?
Pounding sound at low low rpm likely means that the bike is trying to stall. Get the carb jets and passages properly cleaned and check for air leaks.
 
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