94 KDX250SR

[kdx87]

Hi All, its been a while since i have been on. my last bike was the old 200 i did up, since then i got the urge to get a new toy. so i stumbled across a 94 KDX250 SR model, my girlfriend wanted a bike with pillion pegs and this one met all the criteria and was in decent condition, however when i bought it. it lacked compression and was just to tired, as well as someone decided to chop of the kips valves inside the motor. with a KLX front end and rear, fresh top end and kips valves, i got it back to life. its loaded with goodies and is bar none an incredible bike. anyone needs any help with there SR model, ill give it a shot im still learning this bike over.




Engine was ported when being rebuilt, PWK38MM AIrstriker, Vforce reeds, FMF fatty & 92 kx250 stock silencer, the bike uses a flange to bolt the expansion chamber up onto if you go down the route of getting another pipe you will need to take the flange of and weld it to the new pipe. Silicone hoses are from a 92 kx 250 kit. all hoses except the one on magneto side are direct fit, if you cut up the remaining hose you can get it to fit nicely. thinner head gasket from a kx 250 91 model, runs fine on premium pump fuel.

[Jaguar]

are you using premix or auto-lube?

[kdx87]

Jaguar, just the man i need to speak to.Autolube was removed when i had to get the larger intake manifold. It looks like you could tap it in to the larger manifold but i havent tried it.

I believe the KDX cdi is holding the motor back. It hits hard from 7000 to 8500 and thats it. Over revs to 9k but useless power there. Could you help me out. I got the engined worked every which way possible but forgot about the ignition system.

[Jaguar]

I never use autolube after my SR seized when it stopped working. I've disabled it on my Suzuki 100 street bike also. I only use premix, that way I know it's right. I think most autolubes are designed to use normal mineral oil and are a bit "rich" which leads to excess soot and the need to clean the spark plug more often.

ask around on the forum to see if 8500 rpm is the end of the powerband on the 250. That could be the way it is designed since most 250 pistons reach the max safe stress limits (due to the inertia of direction reversals) at 9000. If you exceed the max safe limit then you have to change rings more often and possibly also the top conrod bearing due to the extra stress on them.

[kdx87]

There is more overev in lower gears and will push through to 9500, in taller gears however the over rev fails to provide sufficient power to pull more than 8500. 7000-8500 is the meat of the power. a few kx250 dynos i have looked at seem to produce the identical power curve of this bike and the annoying dip of power at 5500, however they seem to make it to 10000 and then fall flat. i believe the bike is running the stock KDX cdi. perhaps a kx cdi would help out as the engine has been brought further than kx spec.

The klx dash, and vapor gives me every bit of info i need.



A Picture of the intake side. There are 2 tabs on the intake manifold that have to be cut for the vforce reeds to mount up flush. The airstriker is awesome. Before the rebuild there was this horrible bog of the start that no matter what i did to the jetting would go away, the bog has completely gone now. intake manifold and airbox boot are off a 91 kx250. Running 155 main and 42 pilot

[Jaguar]

maybe that lack of umph at top rpm is normal for the 250.
You could try an adjustable CDI (like mine), raising the transfer ports, or a new pipe.

[kdx87]

I guess its just the design of the motor, ive had the cylinder ported quite a bit, im scared to grind anymore away. bit more research shows it just characteristic of the older kx engines to hit hard and then fall on there face. ill be very interested to try your cdi. i believe it should be plug in and play. how do you do the adjustment on your cdi?