KX250 no top end power

[d351re]

Hello,

I recently bought an 98 kx250. Changed the transmission oil, air filter, cleaned the carb and changed the main jet. There was no chance to take it to the wood yet, the weather is still very cold, but I should be able soon. The problem is that I had some opportunity to take a test ride near my house and I have to say that I am not very satisfied. For me it feels like a 4 stroke, has decent low and a nice pull at medium rpm's, strange, but it feels like it fell off on higher rpm's, they just don't make it feel faster. I read a lot of rumours that 250 2t is a hell of a job to ride and that its a beast. It is my first dirt bike and all my friends have 4 strokes, but I believe that it should run way better. The buzzing of the power valve can be heard clearly, so I believe that its functioning and the top end was replaces few hours ago, so I don't think that the problem is there ether. Maybe someone had the same issue and can give me some advice? As for now I feel really disappointed of the 2t.

[umberto]

Run through the obvious stuff first.  I would check your compression using a compression tester, even though the top end was just redone.  Your ring gap could be off, or the cylinder might be worn.  After that, read your plug.  Try a fresh plug and run it up to the point where the issue is happening.  Kill the bike and then see what the plug looks like. Let us know what you find.

[KXDINO]

check the power valve timing make sure it been assembled correctly.

[SS109]

check the power valve timing make sure it been assembled correctly.

Yep, sounds like a classic powervalve problem. Either they aren't timed correctly or something is broke.

[d351re]

Hi all,

Thank you for the answers. I had my first time on the track and it felt better than on a public road. I should get full fmf exhaust, so if the original one is stuck, this should fix that thing. Also I understand, that it requires much more skill to ride 2t and that it is a different kind beast. How I can identify the power valve timing and how I should time it correctly, also maybe then I will loose some mid range power? All in all, now I feel a bit  more satisfied, still people talking that a good 250 2t is a beast and that it is hard to keep the front wheel on the ground till the 5th gear, I don't feel anything like that, but again, maybe there is a lot factors that might cause this.

[KXDINO]

check power valve , take pipe off and power valve cover, disconnect lever shine light in exhaust port pull lever in and out to see if it works , when the lever is pulled fully out the power valves are fully open , if not you need to take barrel off and retime them if there broken replace them . not to sure if there still avaliable from kawi for that model as some models have run out , there is people making this stuff now, i got a set of power valves for a early model kdx 200 from the uk made out of steal instead of alloy they work great and were well priced.

[d351re]

Thank you guys for the help. I will try to take a look on that stuff you mentioned.

[d351re]

Maybe someone knows about 1998 kx250 plastic coversion to a newer ones?

[d351re]

Hello everyone, so now my kx250 has a complete engine rebuild kit with wiseco parts. With a good oil and not a professional riding, how many hours I should be able to take on it? Also, I bought brand new vforce 3 reed valve, however it has a small gap.