Jump to content

05 kx250 new rebuild running hot

Recommended Posts

Just did a fresh build on the eng in my kx250 new crank and complete bearing set, bought a complete jug from someone that did a big boar kit when the bike was new, and new seal kit, it looks like the fluid that is flowing in the radiator is full of bubbles i switched to water and purple ice by royal purple an it didnt cool it down but it still looks frothy as it pumps by the cap, and in the exhaust port there was a few water drops on far right exhaust valve and the side of piston was milky looking, here is a pic threw the exhaust port. any one have any ideas one were i should start? i even put new oversize radiators on but still gets hot and starts running real sporadic high smooth idol with no ting so i shut it down. any help would be great!

IMG_20170506_203943.jpg

Share this post


Link to post
Share on other sites

The "milk" look in oil means the water is mixing with it somewhere, and for it to be in the cylinder but not in the transmission (or is the oil milky there too?) - I'd lean toward it being a warped head or hairline split in your cylinder wall perhaps? I say this based more on my experience with cars than bikes - I just fully rebuilt my first bike which is an '06 KX250, so knowledge is basic I guess. Also, were you sure to seal and seat your cases correctly?

  • Like 1

Share this post


Link to post
Share on other sites

Yeah first things to look at would be the head and it's sealing surfaces then the cylinder base if that fail you may have, like stated already, something cracked somewhere leaking.

Share this post


Link to post
Share on other sites
3 hours ago, Jesse T. Groth-kennard said:

thanks for all your help guys, would you look more at the top of the cylinder or the bottom gasket? 

Remember water and gas don't mix so try clean it dry. Some wd40 in bottom end probably won't hurt.  What you tourqe head to? Head gasket provided with the kit? 

Share this post


Link to post
Share on other sites
thanks for all your help guys, would you look more at the top of the cylinder or the bottom gasket? 


Honestly, you need to work systematically through both ends, to be sure you don't miss anything. If you try to save time by cutting corners on rechecking your work it will end in you having to do another rebuild from what you've explained. Basically, anywhere in the engine where water and oil are able to meet - check it!

Share this post


Link to post
Share on other sites

That's one hell of a cheap and easy fix compared to other potential issues which could have arose from your leak. Good work on finding the culprit though! Brrrap!

Share this post


Link to post
Share on other sites

That's good, easy fix. Make sure you give the coolant a good flush and replace it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×