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yesterday I took out my KDX for a short ride, it wasnt ran in about 2 weeks before that. So I start it up, let it warm up, and start riding and it had a monstrous powerband: wheelie through 3rd gear without leaning back! So then I took it offroad and put it through some bumps and afterwards the powerband mellowed out and got smooth. This isnt the 1st time its happened, and I just want to see whats up. Maybe something with the carb?

Maybe your mix separated some and you were running a little lean?

That's what I think too Wibby....

I imagine it happens more often than we ever think about

My bike usually runs like a raped ape until she fully warms up, but it prolly has more to do with the fuel

mine runs like crap till it's warm, then screams after that..

could be fuel I guess. Or powervalves working then not working then working again.

Mine only runs crappy for about 50 yards, the BOOM!

I guess it could be the fuel, never thought about that. And the power valves, I took off the exhaust to replace the gasket and o-rings a few weeks ago and there was a ton of crud inside the header. It had more power all over the RPM range when I first ran it, even right off idle. I loved it!

I have had the power valves stick from the thick oily residue, until the motor gets good and warm. Then they free up and start moving normally. This will usually manifest itself in a sluggish, trials bike type powerband when cold, though, as the valves should be stuck in the "closed" position.

gregp wrote:I have had the power valves stick from the thick oily residue, until the motor gets good and warm. Then they free up and start moving normally. This will usually manifest itself in a sluggish, trials bike type powerband when cold, though, as the valves should be stuck in the "closed" position.

My bike was a complete opposite though, it ran beyond great right after it got warmed up. Then I took it offroad and it became a little sluggish, lost a lot of the power it had before, even right off idle. Im running 32:1 oil/gas ratio right now, maybe I should lean it out to 40:1 or 50:1 ? I always use 93 octane pump gas

KDXrider1989 wrote:

gregp wrote:I have had the power valves stick from the thick oily residue, until the motor gets good and warm. Then they free up and start moving normally. This will usually manifest itself in a sluggish, trials bike type powerband when cold, though, as the valves should be stuck in the "closed" position.

My bike was a complete opposite though, it ran beyond great right after it got warmed up. Then I took it offroad and it became a little sluggish, lost a lot of the power it had before, even right off idle. Im running 32:1 oil/gas ratio right now, maybe I should lean it out to 40:1 or 50:1 ? I always use 93 octane pump gas

except that's gonna make it richer

Less oil is not the answer. If you run better on a lighter mix, the jetting is wrong for the mix you have. Best to leave the mix alone and fix the jets.

Wibbly is right too, less oil makes your fuel/air mix richer.

If you have a stripped subvalve, it could be open sometimes, closed sometimes.

Thanks guys, I'll check the valves and jetting today when I get the chance. Where should i go to learn how to properly tune a 2-stroke, it will be my first time doing this

Last time my bike lost power mid ride one of the valves gear was stripped. I presumed it was gummed up and soon stripped itself.

mine runs like crap till it's warm, then screams after that..

Wiseco?

I checked out whats going on with my KIPS today, the shaft rotates the side valves pretty smoothly. I took off the left side cover and saw the valves move when I pulled the shaft on the other side in and out. Just to ensure things, I put back on the left cover but left the plastic right side cover off and ran the bike and saw the shaft come out like it should when I revved it. I guess the jetting is what's causing the power band issue. One thing I do remember when I took off my exhaust was when I was cleaning out the crud from the cylinder with a paper towel and accidentally moved the valve at the top. I think it's the main exhaust valve, question is is it normal to move it easily?

fuzzy wrote:

mine runs like crap till it's warm, then screams after that..

Wiseco?

Yup. Was like that with the pro-x too though. I always let the bike warm up completely before I goose it.

KDXrider1989 wrote:I checked out whats going on with my KIPS today, the shaft rotates the side valves pretty smoothly. I took off the left side cover and saw the valves move when I pulled the shaft on the other side in and out. Just to ensure things, I put back on the left cover but left the plastic right side cover off and ran the bike and saw the shaft come out like it should when I revved it. I guess the jetting is what's causing the power band issue. One thing I do remember when I took off my exhaust was when I was cleaning out the crud from the cylinder with a paper towel and accidentally moved the valve at the top. I think it's the main exhaust valve, question is is it normal to move it easily?

No, it probably shouldn't move easily other than a small amount of "wiggle". Also, from behind the left hand cover you can't see all three valves. You have to look up the exhaust with the pipe removed.

Was it cold outside? Cold air = more o2= more power. Once the bikes engine reaches operating temp, the engine should be LESS ABRUPT. I don't think it oil/ gas separation, unless you use a Castor Based Premix.

scheckaet wrote:http://www.kdxrider.net/forums/viewtopic.php?t=1156

I followed these instructions and according to it I need a smaller pilot jet. I don't think I can test the main circuit and throttle response until I get it. My bike has a few mods on it right now though, I guess I'm not used to putting something smaller on an engine that I would think requires more air and fuel