Help, my topend is gone!

Hey guys I have a good one for you. I have a 96 kdx 200 with about every mod done to it. Before last season I had Eric Gorr do his 225 mod. It ran beautifully all last season except the last ride. On the last ride of the year It seem to lose its topend. The bottom was as crisp as always, but the top got real groggy, and it just didn't really hit anymore. It felt as if the power valve wasn't working. So I tore it down this past winter, and didn't really find anything wrong. The power valve had some build up and was a little sticky, so everything was cleaned. I threw a set of rings in it, and rebuilt it. I just got it out and it is behaving the same way. The bottom end seems great, but the is really groggy, and it just doesn't seem to kick in. I have tried different jettings, but really don't think this is the problem. I took the carb completely apart, and flushed it thoroughly. I changed plugs, and after riding it around tonight pulled the plug and it is a nice tan brown color.

Could something be wrong that it isn't advancing my power valve? I am kind of at a loss, because this thing has never really given me any problems.

I am trying to get it ready for an enduro this weekend.

Thanks in advance.
Ryan

XP - Thanks for the speedy response. I went out and tried it. When I rev up the valve snaps open (gear moves counterclockwise), but it is very slow to close (clockwise). I removed the ball completely, and it seem to act about the same. How quick is it susposed to close? When the bike is off(i don't know if your susposed to do this or not) I put a ratchet on the nut, and twisted the valve open, and it snaps back closed pretty quick. I did notice a couple of times it hung up. I don't know if this shows signs of a problem or not? What do you think?

Thanks

Kaw Bill,

I don't know what to tell you about the gaskets, I have replaced mine everytime that I have had my cylinder off. If I had to take it off now without much run time, I would inspect them and reuse if they looked good.

Did you run your bike when you were having this valve sticking problem(over tightened nut)? If so how did it act? It will check the torque of the nut tonight, but am not sure if the power valve is the problem. Something changed the last ride of last season, and I didn't get it fixed with the topend rebuild/valve cleaning. I am just not sure where to look.

Ryan

Ok, here is the latest.

Reeds are in great shape, so I don't think thats it. Thanks though - keep the ideas coming.

I removed the tank, and pulled the petcock out. I wanted to make sure nothing was restricting the flow through the filters. - looked great. I then took the carb apart, snd cleaned everything again making sure the vent lines were open. I changed the main jett to make sure that I wasn't on the lean side. I inspected both boots thoroughly for airleaks. So I put it back together. I then got an in-lb torques wrench and made sure that the main valve rod nut was not over tightened. I then fired it up, and let it warm up completely. When I rode it, the bottom end stilll seemed great. On the top end I definitely felt it wanting to hit the powerband. So the valve is working. When I would get on it, it would start cutting out. Like the engine was stuttering. Could this be related to anything electrical. I really don't know much about the electrical side. What/how do I check it out. I am runnning out of ideas.

Thanks a lot for all of the help and ideas.

Hey guys,

I figured it out. I went to repack my silencer, and found the problem. I have the FMF turbine core II, and the perforated tube that runs down the center was broke off. It was now unsupported at either end. Basically just the packing was holding it up. This must have blocked part of the passage through the silencer. I threw my stocker back on there, and it really came to life. What a relief to have it figured out. Now I just need to order a new silencer. Thanks for all of the help.

Ryan