2004 KX 125 Rebuild

[DP3601]

I recently took on the project of rebuilding a 2004 KX 125. I have completed everything except the motor. I am in need of some help or suggestions as to a problem:

It runs great at low to mid rpm's. When you really get the rpm's up in the higher range there is what feels like a serious vibration coming from the motor. First thought was loose motor mounts. But nothing was loose.  I also pulled the top end to look at the crank as well as the both engine covers to see if I could feel any play in the bearings.  Any ideas what this might be?

Any help would be appreciated.

[Foxx4Beaver]

did you actually measure the play in the big end bearing on the crank?...it could be past it's service limit.
does the magneto/flywheel look ok?

[DP3601]

did you actually measure the play in the big end bearing on the crank?...it could be past it's service limit.
does the magneto/flywheel look ok?

The flywheel looks brand new, in really good shape.  I did not measure the play.  How would you go about measuring the play.  Im kind of a rookie at this... 

[Foxx4Beaver]

with feeler gauges...I couldn't tell you what the service limit is on an '04, the manual I have doesn't go that high...but in the one I have, the service limit is .70mm for side clearance...and .10mm for radial clearance....but that's for a 1990.

you can either call your local Kawie dealer for the specs, or wait a little while, and someone on here might be able to tell you.

wondering if it could possibly be clutch related too...unfortunately, you may end up having to completely break it down to find the culprit...but see if anyone else has some advice before going too far yet.

[DP3601]

with feeler gauges...I couldn't tell you what the service limit is on an '04, the manual I have doesn't go that high...but in the one I have, the service limit is .70mm for side clearance...and .10mm for radial clearance....but that's for a 1990.

you can either call your local Kawie dealer for the specs, or wait a little while, and someone on here might be able to tell you.

wondering if it could possibly be clutch related too...unfortunately, you may end up having to completely break it down to find the culprit...but see if anyone else has some advice before going too far yet.

Thanks for the information, it is very much appreciated.

[KXDINO]

I would look at the big end closely with a good light and a magnifying glass , any greyness on the bearing and its history actually the parts are not to dear , I would put a new big end in and new main bearings and seals, I have a 08 kx125 since new that I kept and had a few season under it belt , I would put a big end in it than the next time it was due a hole crank as the stuffers start to bugger up , I only used oem on the bottom end , they are reliable but the top ends need constant rebuilds with a fast rider on board no more than 6 hrs and change the ring or else they wear the exhaust bridge I also drill the 2 holes on the piston a fraction bigger to allow better lubrication , seem to help also check clutch bearing and plates in case a fibre has broken had that happen on a kx85, another thing I always new when it was time to do the bottom end on it , it always started to vibrate more, hope that helps.

[DP3601]

I am going to go ahead and pull the bottom end apart and refresh the complete thing.  Not knowing how it was cared for from the previous owner(s).  That being said I will go ahead and replace the crank.  I have read nothing but mostly bad reviews on aftermarket cranks.  Anyone have any experience with these.  OEM seems to be the best way to go.

[Foxx4Beaver]

that's a good plan...it's always best to rebuild/replace as much as your wallet will allow, as this will help ensure the reliability of it.
I myself, have heard nothing but bad, bad things about Hot Rod cranks...bad...to the point that my local dealer stopped getting them for customers.
OEM is a very good choice, but I'm not sure you'll find a complete crank available, call and ask your Kawie dealer to check and see if they're available first...you might have to get a rod, big end bearing, etc separately, then rebuild your current crank....but if you have to go that route, consider going with Wossner, as they're rods and pistons are actually quite a bit better than OEM and other aftermarket products.
If you decide to go with Wossner, speak up...as there's a couple good members on here that can set you up with what you'll need.

you can check out Wossner here...
http://www.wossnerpistons.com/

good luck, and keep us posted.

[DP3601]

I can get a complete OEM crank from the dealer for a cool $255.  The Wossner is a cheaper route to go.  Any suggestions on who can rebuild a crank with this kit and what it will take?

[Foxx4Beaver]

check your PM's.

[DP3601]

It looks like the previous owner had put a Anthea cylinder kit on the bike.  All looks great but I did order a new piston kit and gasket kit for their top end.  It comes with two base gaskets.  I have tried to contact Athena and ask if I need to have both gaskets put in but have not got an answer.  Does any one know about this and if it is necessary to have both?

[Foxx4Beaver]

one of them may be thicker than the other, to allow you to change port timing.
I've never used an Athena kit before, so there's a chance I could be wrong...maybe someone else that's familiar with their kits can shed some light on it...or wait until Athena gets back to you.

[DoldGuy]

It looks like the previous owner had put a Anthea cylinder kit on the bike.  All looks great but I did order a new piston kit and gasket kit for their top end.  It comes with two base gaskets.  I have tried to contact Athena and ask if I need to have both gaskets put in but have not got an answer.  Does any one know about this and if it is necessary to have both?

You need to check your deck height first & then your squish clearance.

DoldGuy

[DP3601]

Athena finally got back to me and they said they include two base gaskets in their kits,  they have the standard thickness and a thinner one to increase compression, but only are suppose to use one.  FYI for anyone that might have that same question.

[Foxx4Beaver]

post some pics of your project when you get a chance ...

http://www.kxriders.com/forums/index.php/topic,10040.0.html