HUGE Powerband burst off the bottom! Almost unrideable.

[Fst96se]

Hey all.

I am new to bikes, so keep that in mind here while I post about topics I know little about!

I have three friends that recently bought KDXs... two of them 200s that run great.

One of them is an 04 KDX220. It ran okay when he bought it, but he knew that the Piston issue needed addressed, and did so right away. We found the piston to be a factory piston with a cracked piston skirt.

Top end rebuild was completed (I wasn't there for the re-assemble) and all seemed well.

HOWEVER, all the power is immediately there right off idle, it seems. When you start to accelerate, very quickly there is huge powerband hit and all the power comes on. It is really quite un-manageable. Then power dies off quickly and gets really bubbly on the top end.

I am guessing there is a problem with the KIPS valve.

Can anybody give me some insight as to what is happening, and how to remedy it?

Thanks all!

[Julien D]

The 220 does have most of it's power down low, and needs to be short shifted to stay in the power. It is possible your valves are stuck, so inspecting, cleaning, and repairing anything in that system should be top priority.

[Adamnb1]

I suppose the kips sub port valves could be installed backwards (open when they should be closed). You can verify this, but before that I would probably start by remove the slotted cover on the left hand side, start and rev the engine to verify that the main shaft is being actuated and pulling the kips rods out. Here is a video: http://www.youtube.com/watch?v=2QDJscFPMn4

[bufftester]

Inspect KIPS for proper assembly and operation. Since he rebuilt the top end he really should give the carb a good clean and then run through the jetting guide

[Slick_Nick]

Sounds like he's running it with an aftermarket red power band. Try switching to the blue power band and it should mellow it out a bit...

[cornishwrecker220]

Are you running it without the little ball bearing on the actuator shaft ( next to the removable cap L/H side of the motor ) its held in place by a small bolt & x2 copper washers & a spring ?

[diymirage]

Sounds like he's running it with an aftermarket red power band. Try switching to the blue power band and it should mellow it out a bit...

Just stay away from the orange powerband, that one is way to expensive and gives you nothing but trouble

[ICRage42]

I want to note I was part of the original discussion and the best conclusion is ask your mom.

[Joshmcmillan]

Take off the little round cover on the side of the motor with a flathead screwdriver (about the size of a coin).... and rev the bike, if it moves, the power valve is actuating properly.

[diymirage]

Take off the little round cover on the side of the motor with a flathead screwdriver (about the size of a coin).... and rev the bike, if it moves, the power valve is actuating properly.

but this is no guarantee that the subvalves are installed properly, only that everything moves

[Jaguar]

for less low RPM power just retard the ignition. Rotate the stator plate CCW.
Also you can use a dremel tool to raise the transfer ports. When they are lower than normal the power emphasis is on the lower RPM range.
Getting even more radical you can shorten the pipes header section to synchronize the baffle return wave with the engine at higher RPM

[scheckaet]

for less low RPM power just retard the ignition. Rotate the stator plate CCW.
Also you can use a dremel tool to raise the transfer ports. When they are lower than normal the power emphasis is on the lower RPM range.
Getting even more radical you can shorten the pipes header section to synchronize the baffle return wave with the engine at higher RPM

this may be true but I don't think a new rider should do any of these mod before they get the bike sorted out and running RIGHT.
Doing all of that on a bike that's not running properly is a recipe for disaster.

[Adamnb1]

Take off the little round cover on the side of the motor with a flathead screwdriver (about the size of a coin).... and rev the bike, if it moves, the power valve is actuating properly.

but this is no guarantee that the subvalves are installed properly, only that everything moves

It's likely the best place to start though (which is why I suggested this already in post 3) .. once he verifies things are moving.. you could verify the subvalves are in there correctly. I think you might be able to check this just by taking the pipe off, shine a flash light in there to see if the valves are open when the bike is at rest (access open to the resonator chamber). This thread has some nice info http://www.kdxrider.net/forums/viewtopic.php?p=87851

[Adamnb1]

for less low RPM power just retard the ignition. Rotate the stator plate CCW.
Also you can use a dremel tool to raise the transfer ports. When they are lower than normal the power emphasis is on the lower RPM range.
Getting even more radical you can shorten the pipes header section to synchronize the baffle return wave with the engine at higher RPM

this may be true but I don't think a new rider should do any of these mod before they get the bike sorted out and running RIGHT.
Doing all of that on a bike that's not running properly is a recipe for disaster.

lol.. yup, lets not start with step 29 and 30 of a 30-step troubleshooting process.