Wheezing engine sound and horrible idle

[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

[Floki]

Sounds like the valve train noise, I would,t be worried.

Edit: You probably need to clean your carburetors low end circuit.

[Yarhj]

1. Definitely clean the carburetors, and pay special attention to the pilot and transition circuits. This guide is pretty comprehensive, but feel free to post if you run into issues or have questions. Be sure to use a small copper wire or guitar string to clean out those tiny pilot/transition passages!

2. I'm not entirely sure, but it kind of sounds like you're describing a whine coming from the gas tank, which is perfectly normal on these bikes.

[DaBlue1]

Wheezing? Sounds like your bike might have asthma.

The hanging idle is a too lean idle mixture, either from a vacuum/air leak or dirty idle circuit. Check your vacuum lines, carb boots, and make sure your jets a absolutely clean.

The whinning noise you hear could be normal transmission whine. It can be heard really good on decel and low speeds. A too tight or kinked chain link can also whine some too and also make a pulsing sound.

[chich]

hey guys, thanks for all the help.

i'm sure the sound coming from the engine is completely normal and like i said, it doesn't feel as though its having a negative impact on the performance of the bike, so i'm happy with it.

i'm planning on doing a carb clean this weekend, just out of curiosity, will i / is it a good idea to also do a carb sync afterwards? roughly how long will the whole process take for someone that's never done it before and isn't too mechanically minded?

also what can i use instead of the copper wire? is something line fishing line suitable?

cheers

[Yarhj]

I'm completely unmechanically-minded, and the first time I cleaned out my carburetors it took me about 2 hours to get the carburetors off the bike, and about another 2 hours to clean them out. It took about 3 hours and a lot of swearing to get the carbs back ON the bike (and a lot of swearing at the boots). I strongly recommend doing N4MWD's battery box mod before you take the carbs off -- it takes 30 minutes, and reduces the time required to take the carbs off and put them back on to about 20 minutes each way.

I've heard some people say that they used guitar string for cleaning out the jets, but I'm not sure if it's thin enough for the passageways in the carb body. Just be sure to use something pretty thin, and softer than brass (to avoid scratching anything inside the jets or passageways). I didn't have any copper wire laying around, so I went to home depot and asked them for a foot of some 14-18 gauge copper wire, which cost about $1, and has served me well. Read through the directions here and here for the process before you start, and take your carbs apart somewhere outdoors (so you don't inhale gas fumes all day), and somewhere where you won't lose things if they fall on the ground (especially the little o-rings and washers in the mixture screws).

It is a good idea to do a carb sync after you do anything that affects the intake and engine (carb cleanings and valve adjustments being the most common). Check out this page for directions on how to do it, and how to build your own carb sync tool.

Syncing the carburetors is much simpler than the carb cleaning process, so by the time you need to do it you should have no trouble! The sync process takes about 15 minutes, all told.

One last note -- be extra careful about keeping track of which bolts came from where in your top fairings. On the pregen the top bolts are shorter than the bottom bolts, and if you mix them up you can puncture the tank.

[Floki]

It wouldn't hurt to do a carb sync, that's just something else you can check off the list of maintenance things. I had trouble getting to that stupid screw so I just paid someone to do it. Probably will take an hour to sync the carbs. A day to clean them before hand.

[alex.s]

is there something living in your intake? check the snorkel. it would explain all your issues