Best way to go replacing a '01 bottom end

[MXonaKawi]

I just went through the same exact thing. New OEM crank and all new OEM bearings. Seal & gasket kit from ebay, and new top end. Cost me $200 in labor from a buddy and about $500-$600 in parts.

[needsatopend]

Pro-X Rod kit, Namura top end kit(piston, rings, gaskets, exhaust o-rings, etc), All Balls main bearing and seal kit. Ordered the stuff yesterday.

[Actionman]

Everyone will regale you with tales of how bad Namura pistons are, but as long as your cylinder is in spec the namura pistons are very good in my experience. One thing I do is take a piece of 1000-2000 grit sandpaper and smooth any rough edges around the skirt, intake window, and side pockets where the pin slides in. I do that on any piston I use to keep stress fractures from forming. May not make a difference but I do it anyway.

[needsatopend]

Wouldn't have been my choice, personally I would have gone wiseco forged. My brother has decided he wants to keep the bike and sell his 4 stroke honda. So he goes by his trusty go-to mechanic's advice. Only thing I told him about cast pistons is they normally come in a A, B, C option that are bumped 1 or 2 hundredths of a mm for worn cylinders. Well he placed an order for the standard bore 66.35 without giving it much thought, oh well hopefully it wont grenade on him

And here is the bike without those terrible graphics! much better

[Actionman]

I used the c piston in mine. It should be fine Id imagine. Looks good!

[shrubitup]

pro-x sells good bearings and seals.  Would not buy any rod/piston from them, all wossner, all the time.  I have pictures if you need to get a better idea why not to run a pro-x piston.

Last I knew ProX was made by ART who makes OEM pistons.

[shrubitup]

Everyone will regale you with tales of how bad Namura pistons are, but as long as your cylinder is in spec the namura pistons are very good in my experience. One thing I do is take a piece of 1000-2000 grit sandpaper and smooth any rough edges around the skirt, intake window, and side pockets where the pin slides in. I do that on any piston I use to keep stress fractures from forming. May not make a difference but I do it anyway.

Used many Namura "junk" pistons without one issue.

[KXDINO]

I bought a kx250 01 off a guy , only wanted the frame etc , any way he was running it for so long with the big end worn the piston was kissing the head , had massive play , so the oem rod is a pretty strong unit to take that abuse . On another note them motors respond well to porting , there a fair bit you can do to them.

[Foxx4Beaver]

On another note them motors respond well to porting , there a fair bit you can do to them.

+1
all I did was clean up the casting flaws on my '00...it has more low and mid range than my brand new '04 did.

[needsatopend]

Ok here's where I'm at.

Got the crank back balanced with pro-x rod kit installed, and installed with new main bearings and seals.

Also the crack welded...





Installed the transmission tonight. Going to make a thread adapter for the case puller to install the left case half

[needsatopend]

All together now



Here is the home made 2 in 1 case splitter / left case installer

Center threaded rod has a rounded end at one end for a case splitter,  and a thread adapter at the other end to grab the crank at the flywheel side



Clutch basket holder tool

[needsatopend]

All done



Beside the DX

[Actionman]

Before I got my 2000, I thought kx's were ugly as hell (Im a suzuki RM fan); but with a set of green side panels the L models are very nice looking bikes. White is ok as well tho. You did a good job!

[sandblaster]

One thing I do is take a piece of 1000-2000 grit sandpaper and smooth any rough edges around the skirt, intake window, and side pockets where the pin slides in. I do that on any piston I use to keep stress fractures from forming.

I also do it to keep the sharp edges from scraping the oil off the cylinder walls during break in.
It may be unnecessary but I feel better doing it.