KX500 water pump modification

[Sandblaster]

Myself and another member Motorrad will be working to improve to cooling capacity of the KX500 engine by modifying either the water pump cover or shimming the impeller to decrease the clearance between the impeller and the water pump cover.
This was his idea
By doing this we should be able to increase the coolant flow and decrease the operating temperature much in the same way that the after market covers and impellers do.

kx500 water pump cover modification.JPG (103.58 KiB) Viewed 27840 times

Initial test are showing the impeller to cover clearance is about .115"
No wonder these pumps cause cavitation at higher RPM's.

Stay tuned as there will be much more info coming on this project

[Friar-Tuck]

Excellent Blaster!
Thanks for Sharing! I often wondered how many items like the impeller and the w.p. cover from the 250 just might fit.
However a very limited budget puts the Kai-Bosh on a lot of experimental tinkering!
I'm pretty sure there was a clutch basket project a while back that was successful too.
Thanks again and keep up the good work!
Tuck \o/

[Sandblaster]

Hey Tuck.
Were you talking about the 89 KX250 basket fitting the 89-04 KX500?
Or were you talking about the klx klr kdx experiment?
Also, if you have some good ideas and need extra parts, let me know as I am willing to share to further K5 interests

[Sandblaster]

I will be cutting a spare cover in half to make a tool for measuring the clearance between the cover and the impeller.
I will also be looking at the profile of the impeller vs the profile of the cover to see if machining of the impeller will be required to make this project better
Some people hate going to work on Monday.
While it can be stressful at times.... I can't wait to get there tomorrow

[Sandblaster]

Now that Motorrad is a member of this site I can say that he is the member of the other site (KXRIDERS) where we started working on this issue.
It's great that Motorrad had this Digitron to point out the problem in the first place.
So here is the deal.
Check out the clearance between the impeller and the cover.
In this example I am using a Athena water pump gasket that measures .021"

KX500 WATER PUMP IMPELLER CLEARANCE.JPG (37.09 KiB) Viewed 27831 times

So, depending on how you want to measure the clearance we need to shim the impeller approximately .080-.085" to take up the space.

KX500 WATER PUMP IMPELLER CLEARANCE 2.JPG (38.81 KiB) Viewed 27831 times

With the correct amount of spacers you can get the impeller where it barely touches with no gasket.

KX500 WATER PUMP IMPELLER CLEARANCE 5.JPG (42.28 KiB) Viewed 27756 times

Then, remove the cover, install your gasket, replace the cover, torque the bolts down and spin the drive gear on the back.
It should spin with no scraping and since most gaskets I have measured are the correct thickness range, you should now have the correct clearance.

KX500 WATER PUMP IMPELLER CLEARANCE 6.JPG (32.93 KiB) Viewed 27756 times

Incidentally, yes I ruined a perfectly good cover to do this.
I do have the other half if someone want's it for the cost of postage

[Motorrad]

Who is this Motorrad guy you speak of? he sounds like a total douche...

would be cool to offer it up as a "loan a tool" to be passed from one member to another...

[Sandblaster]

Who is this Motorrad guy you speak of? he sounds like a total douche...

would be cool to offer it up as a "loan a tool" to be passed from one member to another...

I have no problem with that, who needs it next?

[Motorrad]

Who is this Motorrad guy you speak of? he sounds like a total douche...

would be cool to offer it up as a "loan a tool" to be passed from one member to another...

I have no problem with that, who needs it next?

Im trying to talk USMC500 into it. As his motor is as much mine as his.. (If you ask me)

[Sandblaster]

Just a rough estimate but it appears that the impeller shims reduced head temps by approx 20%.
Motorrad will be doing more testing and will let us know..

[Sandblaster]

Oh, USMC 500 should have the test fixture in about 2-3 days