[chich]

Hey guys,

Ok this is going to be really hard to explain as I’m not mechanically minded in any way however please bear with me.

I’ve brought my little ninja 250 (2009) out of retirement as there was a period of 18ish months were it was inadequately stored and neglected. To get it fighting fit I decided to replace the oil + filter, complete coolant flush and changed over to engine ice, new spark plugs and new air filter. This seems to have brought it back a massive amount however I’m still having two problems:

1. The bike would idle (when fully warm) at around 500 rpm and then die. Also only when at under about 3k rpm, when I would open the throttle, there was a clean 1 second delay between when I twist my wrist and the engine starts to increase in revs. while at anything higher than 3k rpm, there is an instantaneous response when opening throttle.

My thoughts would be that the carbs are gummed up to at least some degree that isn’t allowing enough fuel to go through with no throttle pressure, does this sound about right or would I be looking at a vacuum issue? As an interim solution I’ve tried adjusting the idle knob on the bike to bring it up to around 1,250 rpm (whilst bike was warm), however what I found was that when I opened and closed the throttle, the revs would go up to for example 7k rpm, stay there for several seconds, then gradually start returning back to idle. No idea what this about or why its happening.

2. I’ve began to hear this wheezing sound under very specific conditions. It’s definitely not coming from the exhaust as that sound remains the same, however as I can only provoke the sound whilst riding, best I can say is that it sounds as though the noise is most noticeable when putting my ears closer to the handlebars (ie. Leaning off the bike in either left or right direction doesn’t give me a better indication of where the sound is coming from).

Ok so these are the ways to get the bike to produce this wheezing sound:

1. Travel at around 40-50 kms (30ish mph) and delicately play with the throttle where you keep bouncing back and forth between accelerating and decelerating the bike (if this makes any sense). It seems that this sound seems to be produced rather easily whilst travelling at low speeds (20 – 60 km / 15 – 40 mph) with a low rev range (3-6k rpm) with the gearbox fully engaged (no touching the clutch lever) and allowing the bike to decelerate/engine break naturally on its own. This will produce a continuous sound that will last for as long as these conditions are met.

2. High speed (70+ kms / 50+ mph), higher revs (6k+ rpm), release throttle and pull in the clutch lever. This will produce the sound for a second or two and then it will disappear.

I am absolutely stumped as to what this sound could be and furthermore I have no idea what may have caused it. Literally just prior to the 18 month storage, the bike was serviced by the mechanic and was otherwise in perfect condition. There’s currently 17k kilometres on the clock and it doesn’t feel as though whatever is causing this sound is having any negative impact on the bikes performance (gears feel fine, accelerating is fine, etc).

To try and better describe the sound, think the same sound as the exhaust makes with much less (zero) bass, still having the same high and low pitch however oscillating out of phase with the exhaust.

Does anyone have any ideas on any of this?

Thanks