Maintenance & Technical > KX250 / KX125
Kx250 1999 engine performance upgrades
Friar-Tuck:
Hey SC,
I just went through a 99 kx250 a few months ago for someone at work, once you get the piston /crank/bearings sorted, look for excessive play in the powervalve parts.
The bike had been rode hard and put away wet, (Heck it was 15yrs old!) the clutch basket was pretty well notched and the fibers were burnt.
I'm sure you will have a good look at all the internals, as we also had to replace third gear and several bearings and seals.
My buddy had ordered a bunch of parts before I had gotten the engine torn down and ended up in a budget pinch.
The forks needed seals and bushings, the swingarm and suspension bearings and seals were toast and the throttle was falling apart along with the cable. Brakes and rotors oy-va... I guess what I'm saying is make sure you have a good final parts list before getting the "Goodies."
All I did to the engine was cleanup the casting flaws,roughed up the intake and matched the ports.
(The sizing of the ports were a few mm's off and it wasn't done on purpose) .
There was probably 3mm or so of play in the main valve and the exhaust barrels would not line up correctly no matter how I tried to time them.
We had to replace all the powervalve parts, My buddy couldn't understand how only a few MM's could make such a big difference, until he rode the bike with everything working...
He had a steahly flywheel weight, Boyesen superstock reeds, aftermarket air filter and an fmf pipe and silencer.
He did say he was gonna change the gearing as the stock set-up was just a little to fast in the woods we have around here.
Sorry to prattle on... :-D
Blaster & Foxx have a lot of experience and both stand up guys, their word is good as Gold.
Tuck\o/
swordcombat:
--- Quote from: sandblaster on October 21, 2015, 12:05:41 PM ---You buy a rod kit and have your crank rebuilt with it.
You can send your crank to a rebuilder and have it balanced.
--- End quote ---
Sorry i meant wiseco cranks as wossner dont make them , but reading up i hear bad things about wiseco cranks and some good things about hot rods , but may just get mine rebuilt , thanks for the advice buddy
swordcombat:
--- Quote from: Friar-Tuck on October 21, 2015, 12:18:44 PM ---Hey SC,
I just went through a 99 kx250 a few months ago for someone at work, once you get the piston /crank/bearings sorted, look for excessive play in the powervalve parts.
The bike had been rode hard and put away wet, (Heck it was 15yrs old!) the clutch basket was pretty well notched and the fibers were burnt.
I'm sure you will have a good look at all the internals, as we also had to replace third gear and several bearings and seals.
My buddy had ordered a bunch of parts before I had gotten the engine torn down and ended up in a budget pinch.
The forks needed seals and bushings, the swingarm and suspension bearings and seals were toast and the throttle was falling apart along with the cable. Brakes and rotors oy-va... I guess what I'm saying is make sure you have a good final parts list before getting the "Goodies."
All I did to the engine was cleanup the casting flaws,roughed up the intake and matched the ports.
(The sizing of the ports were a few mm's off and it wasn't done on purpose) .
There was probably 3mm or so of play in the main valve and the exhaust barrels would not line up correctly no matter how I tried to time them.
We had to replace all the powervalve parts, My buddy couldn't understand how only a few MM's could make such a big difference, until he rode the bike with everything working...
He had a steahly flywheel weight, Boyesen superstock reeds, aftermarket air filter and an fmf pipe and silencer.
He did say he was gonna change the gearing as the stock set-up was just a little to fast in the woods we have around here.
Sorry to prattle on... :-D
Blaster & Foxx have a lot of experience and both stand up guys, their word is good as Gold.
Tuck\o/
--- End quote ---
Oh yeah dont worry buddy , this is a slow full rebuild and the parts in total come to about £1500.00 GBP , but i, doing it by spending £200 per month.
Well the forks i have completley rebuild with seals and bushings with fresh oil , every bearing will be replaced to.
The barrel needs a re sleeve and the con rod has no up and down play but
Lots of side to side play to the extent were the conrod has wear marks on from the sides of the crank.
Also power valve play? In that do you mean just loose in the port?
I was actually thinking of putting a 2002 barrel on my engine and buying the matching valves.
sandblaster:
Wossner does not make a complete crankshaft but the picture I posted is a 99 KX250 Wossner connecting rod kit.
You can see our build here:
http://www.kxriders.com/forums/index.php/topic,15682.0.html
Rebuild your OEM crank and have it rebuilt with the rod kit.
It is as good if not better then the stock kit.
In my opinion you will end up with a superior crank then either a Wiseco or Hot Rods crank.
Foxx4Beaver:
--- Quote from: Friar-Tuck on October 21, 2015, 12:18:44 PM --- Blaster & Foxx have a lot of experience and both stand up guys, their word is good as Gold.
Tuck\o/
--- End quote ---
thanks for the kind words Tuck!....I've always had a lot of respect for your answers and input as well. :-)
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