03 KX250 troubleshooting

[TJXK]

Late September I was riding my 03 KX250 at the Oregon dunes when it sputtered and died out of no where.  I thought this was suspect so I got off the bike and moved the kick start by hand slowly.  There was a metal on metal squealing sound that could be heard as the piston moved through its stroke.  I didn't want to kick the bike over and try to start it as I thought something was seriously wrong.  So I spent the next hour or so pushing it to a spot where I could pick it up with a vehicle.

Since I finished my RM125 top end finally, I brought the KX inside.


I worked on it until I got the cylinder head off.


Apparently the last person to have it off used some clear gasket sealer of some sort instead of a proper gasket.  They also over torqued the nuts.

I fully expected the cylinder to be scratched up or a ring to be damaged. 


It looks fined to me.  The cylinder walls look perfect and the top of the piston is brown/black with no damage.  There is zero metal on metal noise as I move the kick start. 

So my question is what should I look for?  I plan to inspect the exhaust valves, reeds and maybe remove the cylinder so I can further inspect the piston/rod/crank bearings. 

[sandblaster]

Your right there so I would pull the cylinder and inspect the crank.
The coast takes out a lot of top and bottom ends on 250's as they have to work a bit harder.
The last 03 we got in had the main bearings frozen.... It happened at Winchester bay 

[TJXK]

What is the best way to inspect it?  Should I just do a visual of the crank with the cylinder off and check the crank bearings for looseness by pulling on the pistonrod?

[treedodgingfool]

The 2str stall-n-die, sounds like the lower-connecting rod bearing.  Pop the top-end and piston off, get a hold of the rod and see if it has any up/down play. Inspect the entire assembly carefully for any metal bits or flake.  Pop the ignition cover off, move the flywheel up/down to check for main bearing play. 

[The Flyin Hawaiian]

That clear sealer is from the headgasket. Kawasaki puts a thin sealer on them and it usually comes of when the head is removed.

[sandblaster]

What is the best way to inspect it?  Should I just do a visual of the crank with the cylinder off and check the crank bearings for looseness by pulling on the pistonrod?

Once the cylinder is off spin the crank.
If it is rough anywhere, it's time to split the cases.
To check the connecting rod while the top end is off, put a feeler gauge between the connecting rod and one of the two crank halves.
I don't have the 03 service specs recorded but I believe it is the same as the 92-02   New .018-.022" and the Service Limit .028".
The closer you are to .028" the more you should consider replacing or rebuilding the crank.

[TJXK]

Thanks guys!

[TJXK]

I finally got back into working on this bike and will hopefully have the funds to do whatever needs to be done later this month.

I took the flywheel cover off to check the crank bearing on that side.  There's no play or leaks. 

Next I took off the cover on the other side and did the governor spring mod described here:
http://www.thumpertalk.com/topic/706814-how-to-2003-kx-250-powervalve-mod/
I used an 04 kx250 spring instead of a spacer.

Next I removed the cylinder.  The cylinder looks good.  The piston checks out as well.  The rod has what I'd consider to be a slight up and down play.  Seems to be okay, but I'm no expert.  It's definitely not anything close to this: 
https://www.youtube.com/watch?v=hFuEJdOpPGY

As I spin the crank it does seem to have a little bit of roughness, but again I'm not sure what is and isn't normal and it has sat for months so I dunno if it might not be as lubricated as normal.  I'm fairly certain one of them is shot though since way back when it died it had a squeaky metal on metal noise and roughness to it. 

Thanks for reading my novel if you made it all the way through.

[TJXK]

Also when it's top dead center the spots on the crank next to the rod should be gold right?  On one side it's gold, on the other it's black, almost like it was gold but over heated and discolored.

[sandblaster]

The rod has what I'd consider to be a slight up and down play. 

If you can feel up and down play in the connecting rod, it's done.
Rebuild it or get a new one along with main bearings seals and whatever else you may need while you have it apart.
Look carefully at the output shaft bearing on your trans as they are a known heavy wear item.
I would personally replace all the bearings, seals and clips on the trans just because.
I just ordered all those parts for my SM bottom end today as I plan on rebuilding it sometime in the near future..

[Foxx4Beaver]

The rod has what I'd consider to be a slight up and down play. 

If you can feel up and down play in the connecting rod, it's done.
Rebuild it or get a new one along with main bearings seals and whatever else you may need while you have it apart.
Look carefully at the output shaft bearing on your trans as they are a known heavy wear item.
I would personally replace all the bearings, seals and clips on the trans just because.
I just ordered all those parts for my SM bottom end today as I plan on rebuilding it sometime in the near future..

+1....when I did my 2000 250 over...everything but the tranny and cases were replaced...why?...because I planned on keepin her for a while

I actually thought about selling it over the winter...but, it's the most reliable bike I've ever had...it don't matter if it's sat for 4 days, or 4 months...ONE kick, EVERY time. There's no way I can sell a bike that's that reliable.

[TJXK]

Sounds good.  I plan on keeping this bike for a long time so when I get the cash I'll start on my first full rebuild. 

I'll update again when I actually start.  First thing on the list is a long fold out table to lay everything out properly.  I guess I'll need a case splitter and flywheel puller as well.

[Foxx4Beaver]

I'm willing to bet you could find a member or two that would let you borrow their pullers/splitters...maybe for a 30 pak

[TJXK]

I'm willing to bet you could find a member or two that would let you borrow their pullers/splitters...maybe for a 30 pak

Even though I will probably rarely do a rebuild like this, I wanted to have my own set of tools.  I ordered everything I needed from the cheapo tusk brand and it only came to like $100.  Although I won't be able to start the build until I move later this month and get everything organized.  I'm also starting a new job at the same time so I'm pretty busy.

Thanks for the offer though. 

[Foxx4Beaver]

nothing wrong with the simple Tusk hand tools...at least the ones I've used always did the job.