Well let me start just bought a 90 kx 250 pretty beat up but it will be my third restoration of a dirt bike. just ordered the manual. the top end is shot does any one know if the 1990 model has a nicasil or plated cylinder or is it not plated. also the tab or keeper on the side of the motor where the clutch cable goes thru is busted off any ideas on fixing that? one last one tried to remove the steering stem from the neck but the top bearing seems to not want to let it go is that pressed on? cant see how but you never know.
ANY advise would be great.

 

For $600 for a cylinder, it must be gold. sheesh. Not sure on if it is lined or plated. Use a magnet to determine and a lined cylinder will show a darker overlap at the mating surfaces.

congrats on getting the manual, that puts you ahead of the game.

The clutch cable case bung/bracket? If you can weld another bung/bracket in place would be good, otherwise a new case is needed I think. You have a pic of this?

Welcome to KF

 

Here is a pic of that clutch tab

 

Here is the frame after prep and 1st coat zinc primer, second coat reg primer and two color coats and 2 clear coats finished it today. Never did get the neck apart, so i painted around the forks.beariongs look ok i'll just grease them as best as possible i guess.

 

Nice, but the overspray may prove detrimental. forks, rims, tires. Next time just pull the bearing assembly. Yes, another possible tool, but you know that things were done right while riding. The comfy thing scenerio, looking good, congrats.

 

Stock, the cyl is nikasil'd. Used to ride a '90 kx250 but can't remember if the clutch cable boss was on the case or the cover. Also can't remember what the case was made of in regards to welding. Anyway the bike was fast for it's time..I remember my brother racing his in enduro's and it sounded unholy working thru the tight woods...Good Luck with the build!

 

I also have a 1990 KX 250 project that I am working on. Not as extensive are yours, but more about getting it to run right. I put a new plug in it, did a compression check and got 145 psi. I cleaned the carb twice, and also cleaned the air breahter. Changed the crank case oil, which was a little frothy, sort of like a moca milkshake, but not too bad.

It starts and runs well at idle, but sounds like it is running rough at high RPM and is very under powered.
I road it yesterday at a track and coming out of the corners in 2nd or 3rd, grabbing a hand full of throddle, it will not even lift the fromt tire off the ground.

Not sure what to check next. Will start with the reeds, but I think they are ok.

Read somewhere about power exhasut valves? not sure about these or what can go wrong with them, or how they are repaired?

Anyone have any ideas for me.

Airwinona