EX250 Engine Rebuild Notes

What to replace

The MAIN thing is the bearings. You need to know the COLORS of your bearings and that will be different for each motor. So sadly, at the first rebuild you wont know this ahead of time so you cab have parts in hand when you start the project.

Absoultly needed for each rebuild: You need to know your bearing colors, it isn't as simple as just ordering bearings. There are three different thicknesses. Highly recommended: Low Priority: You dont really need if you dont tear them: Crank/Oil Mod

whats the "Crank mod for oil delivery"?

chamfering of oil delivery holes to get directed oil flow to bearings. Have the crankshaft shop do it while they polish the crank.

Picture of Oil Baffle Mod


For cleaning the cases and parts, what type of cleaner should i used? The book reccommends a high flash point solvent, but what is that, brake cleaner or Carb choke cleaner?

Kerosene or mineral spirits. G-Force uses a solvent tank, then sprays the heck out of the parts with brake cleaner and then sprays the heck out of everything with compressed air.


What type of gasket maker do i use to seal the cases? There is about 5 different types of RTV gasket maker.

Mike Norman says to get Toyota FIPG Oil Pan Sealant. It ain cheap (about $18/tube) but it works as gasket sealant AND for safety-locking.


How do i determine what bearing inserts to get if the paint marks are gone?

To be completely sure, micrometers. You might need to take it to a machine shop to get accurate measurements. But you can tell what they *probably* should be from the marks on the crank and the cases. I would try the ones indicated by the marks, plastigage them, and go from there.

Mike Norman says that for a Kawasaki EX-250 1988+ the bearing colors are usually:
Balancer = Blue
Mains = Yellow
Rods = Brown
The microfiche on Buykawasaki.com has all of the part numbers to correct colors.


aside from the oil retaining rings and expander, there's two piston rings in the package, one darker w/ "RN" stamped on it, and the other lighter ring w/ "R" stamped on it.

which ring goes on top? i'm assuming the lighter one ("R") but i've decided to stop and ask first.

Frank Mazur syas that the R stamping goes face up the lighter color ring is a harder composition that deals with compression and heat is the top ring. The darker color can help with compression and oil retention is the second ring

...And adds that the light color ring is the top ring. Any letter, script or numbers go face up. The lighter ring is for heat and sealing, while the darker ring is for sealing and helping to scrap oil IF they are both the same color then ...who cares?

Valve Height

valve_height.txt - Mike Norman on valve clearances
valves.txt - Mike Norman on valves and aftermarkte cams
valves.txt - Mike Norman on engine mods
Barbie Valve Height Adjustment Guide - Mirror of the famous original