Need help with a zxr250 idling rough and not revving out

MadHatter · Post by **MadHatter** » Thu Mar 30, 2006 10:33 am

Hi guys,
I've recently come into posession of a C model zxr250, it had been sitting in a paddock for a year or two but is otherwise in pretty good nick.
I've been bored, so I cleaned it and fixed the basics up, cleaned the carbs.. new filters etc.
It starts now, but it idles rough (eventually slowly conks out) and doesn't rev past 16000rpm. The throttle response is also very sluggish.
The needles and seats were fine, no visible wear, it looks like they have been replaced recently. The only thing i didn't get to was the pilot circuits.
I set the screws 2 and 1/2 turns out.
The air filter is new.
It's hard getting information for this bike as it was a grey import.
Any gurus have any Ideas on what might be the problem?

mike-s · Post by **mike-s** » Thu Mar 30, 2006 1:04 pm

want me to bring the carbtunes by your place again on saturday and see if the carbs are out of synch? that may help it a bit, but it did feel like they were reasonably spot on before...

Duane · Post by **Duane** » Thu Mar 30, 2006 2:26 pm

Balance carbs
Replace sparkplugs (or atleast check to see theres spark, and they aint filthy)
Check fuel (how old is it)
Check idle setting
check Fuel filters. (spesh replacable inline ones)

Stereo · Post by **Stereo** » Thu Mar 30, 2006 2:38 pm

Losing compression maybe?

is it blowing any blue smoke?

Duane · Post by **Duane** » Fri Mar 31, 2006 6:46 am

Also might be worth lubing up your throttle cable, by the sounds of it if it's been sitting around long enough without being used it's probably dry as a chip

MadHatter · Post by **MadHatter** » Fri Mar 31, 2006 10:54 pm

Duane wrote:Balance carbs
Replace sparkplugs (or atleast check to see theres spark, and they aint filthy)
Check fuel (how old is it)
Check idle setting
check Fuel filters. (spesh replacable inline ones)

I did all that first thing, there is spark.. the plugs look new.
New Fuel
Idle on maximum or it conks out
Fuel filter was replaced and tank flushed.

MadHatter · Post by **MadHatter** » Mon Apr 03, 2006 3:58 pm

still.. won't.. go..

Gosling1 · Post by **Gosling1** » Mon Apr 03, 2006 6:10 pm

it could just be a dud battery mate - check the voltage and also the fluid level........if anything looks remotely *suss* (including white cells in the battery), flick it and buy another one......maybe that will fix it.....its worth checking out anyway.

mike-s · Post by **mike-s** » Mon Apr 03, 2006 10:34 pm

[mike-s ) have you measured the coil resistance & made sure they were in spec?
[mike-s ) like the HT coil
[hat|zz ) no
[mike-s ) alternator, charge, etc?
[hat|zz ) battery is new
[hat|zz ) charge good
[mike-s ) it just staggers and dies, doesnt it?
[mike-s ) slow down, chuggida chuggida stop
[hat|zz ) yeap
[hat|zz ) chuggida fucking chuggida

Gosling1 · Post by **Gosling1** » Mon Apr 03, 2006 10:53 pm

OK if it has a new battery fitted, that *probably* eliminates the battery as a potential problem......

You said that you didn't get to the pilot jet circuits ? These control the idle settings, in conjunction with the mixture screws......I think you might need to rip the carbies off again, and clean out the pilot jets with an air duster....clean all of them with an air duster, and check the flow of juice from the tank with the tap on 'Prime' and the bowls off.

MadHatter · Post by **MadHatter** » Wed Apr 05, 2006 2:10 am

took carbs out again, did pilot circuits and EVERYTHING again
tested with an different fuel tank
Same problem

mike-s · Post by **mike-s** » Wed Apr 05, 2006 1:00 pm

http://www.adventuremotogear.com/twinma ... 5TC7G1GR78

The benefits of correct carburetor balance
With use, the chain of cables, rods and linkages that connect the throttle to the carburetors will stretch and change their tolerances which results in the carburetor sliders or butterflies operating at slightly different times from one another. This produces an imbalance in the carburetion of the engine due to unequal amounts of air entering the cylinders at any given time. Carburetor balance, or synchronization, is essential for the efficient running and longevity of your engine. Any imbalance in the timing, or amount of, throttle opening amongst the carburetors on your engine will result in reduced performance, poor throttle response, excessive fuel consumption, increased vibration and increased stress on the crankshaft and bearings.

http://www.twisty-roads.com/FAQs.htm
Q: How will my motorcycle run at high elevations?

A: Due to the reduced amount of oxygen at higher elevations, the fuel mixture becomes rich. You can expect about a 20% loss in power, rough idle and slow throttle response. Spinning the motor at slightly higher rpm's helps to keep things cleared out and we've never had a bike on tour that refused to run or was damaged by running rich. It is most apparent at altitudes above 10,000' where the scenery is so spectacular and the roads so twisty that you won't care if your bike runs a little rough.

http://www.eric-gorr.com/twostktech/carbtuning.html
Crankcase air leaksÑAir leaks can occur at the cylinder base, reed valve, or the magneto seal. Air leaks make the throttle response sluggish and may produce a pinging sound. That sound occurs when the air-fuel mixture is too lean.

So first thing from a couple minutes of googling to check is let me bring my mates carbsynch over and lets give it a go, then failing that, lets see if its got an air leak.

Gosling1 · Post by **Gosling1** » Wed Apr 05, 2006 7:46 pm

MadHatter wrote:took carbs out again, did pilot circuits and EVERYTHING again
tested with an different fuel tank
Same problem

time to check camchain tension - and then valve clearances......you might have some tight inlet clearances........

Its always a process of elimination.......1 thing at a time.