To start this off had bottom end rebuilt after seized by infinity motorsports 2 rides later blew the top end in oct wells rebuilt it took it glamis ran 32/1 ran great. That was 6 months ago bike hasnt been started since got some gas at first bike would start as soon as i give any throttle it would shut off check my spark plug its black a lil wet local bike shop is closed. I put my spark plug back in kept firing it still did the same thing after about 30 kicks it would idle but as soon as i gave it any throttle it would go high rpm and not really go bac down the throttle is returning to its position. So any advice would help i checked my air screw 1 1/2 turns out im goign to get a new spark plug tomorrow but is there anything else. i havnt touched the motor since glamis.

You need to pull the carburater off and clean the jets. Sounds like there is some junk in there. Also make sure your air filter is clean.

man its hard to understand what you are saying.

so you give a little throttle and the rpms stay high even though you are sure the throttle is not sticking?

wish i could help...kind of stumped. sounds like your plug is fouled if its black and oily.

not sure why you are idling high though a fouled plug should do the opposite.

Fouled out the plug.

The 98 KX were notorious for doing this. You need to run 40/1 instead of 32/1 to start off with. Next you need to clean your power valves, but you will need a sevice manual to tell you how to time them.

Basically when your Powervalves are really grimey more goo sticks to them and then runs down the cylinder and into the bottom end after sitting for a while. As soon as you start it up, it moves into back into the cylinder and fouls your plug.

Also blow that sucker out before you hit the kill switch, that helps quite a bit. Just rev it to the moon a few time and then shut it off. I would try this first before getting into the powervalves....

*forgot to add I've had every year of KX since '92, so I speak from personal experience*

I had the high revving problem with a 92 KX250 I had awhile back. Mine would only do it when I first started it, then it would slowly work it's way down to normal. I cleaned the powervalves and that cured some other issues it had, but not that.