Top end help with 99 kx250

[kxr1der87]

I just the bottom and top end on my 99 kx250. The piston skirt dropped when the motor blew. I just got to put it all together and when i put the top end on and torque it down and use the kick start to test it the piston gets jammed up right above the exhaust ports. The rings arn't snagging on the ports and yes i have the dowel pins in, but you can see that the piston is tweaked forward a little bit. Any ideas of what this could be?? Im guessing bent crank rod or the cylinder is out of round.

[jimzumba]

Bent crank shaft and bearings more than likely....
Best bet...
Ebay- Buy a new complete crank for 150 and start over...thats what I wound up doing with my 99 kx250 an the thing is a running champ now.

[HELLDOG488]

CHECK cylinder for wear. (egg-shaped)
Piston slap is main way for piston skirt breakage.

[kxr1der87]

Yea, you can see where the plating started to wear off at the top of the cylinder. But its binding below that and on the opposite side, but im sure its worn down. Im heading over to my uncles shop in a few to measure it. Let you know how it goes. As far as the crank, everything seems fine, no up and down play with the bearings, spins freely in the case but i wont rule that out.

[kxr1der87]

I check the cylinder and it seems pretty worn but its not horrible(at least i dont think so). But has anyone every used the millenium technologies exchange program? Seems legit i was just wondering if it was worth it.

[HELLDOG488]

They do very good work and i have used them for yrs at the shop i work in.

[nd4speed]

millenium technologies is a top rated company and I believe they handle a lot of NASCAR business if that tells you anything.

[kxr1der87]

Thanks guys thats all I need to know haha.

[kxr1der87]

Im just doing a follow up, I finally got this thing running. It ended up being a bent crank rod. Just a few more loose ends and it'll be good to go, thanks for the help.

Another thing, There is a knocking sound coming from the top end, you can hear it when its running and when its not running. Its right when the piston reaches the top of the cylinder and starts to go down again. Any ideas what i should check? This is where the plating is most worn too which could probably have somthing to do with it.