YZ426 Overheating.....Need sugestions

[LT250Racer609]

Ok well, I origionally had a problem overheating with my YZ426 Hybrid when I had my stock 250R radiator in there...which that would be a obvious givin. Well I bought a AFCO racing radiator (This exact one off ebay...http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=ADME%3AX%3AAAQ%3AUS%3A11&viewitem=&item=120158307132) and well, it overheated lastnight when I was riding hard with this radiator. I dont have my radiator shrouds on yet, and my quad is due for a oil change (im running the wet sump kit) and a regular 50/50 mix for coolant. I would never think it would overheat with the oversized rad. while I was riding. It got to the point where it wanted to die so I took it easy in first gear from my track to home and the whole way, my header pipe was glowing Bright red....as soon as I pulled in my driveway, and shut it off....coolant poured out of the overflow everywhere....would it help if I ran engine ice?? Im modding my shrouds to fit as we speak.

[2muchquad]

Puttin home in first gear was probably a mistake.The motor cant get much cool air when your crawling.Yzfs run hot even stock with a bigger radiator theres not much you can do unless you try a yfz 450 fan to help supplement the rad.What kind of riding you doing?Slo speed stuff will boil the coolant in no time,regardless of the rad size.The yzf mx motor was built for racing,thats why its got a higher comp piston compared to the quad motor.You gotta letter rip.Also make sure your jetting isnt too lean ;)

[LT250Racer609]

Im a Expert MX Racer. I was doing laps on my track and After I climbed my huge hill 3 times in a row, right when I got to the top the power started breaking up and thats when I putted home in 1st gear, shut it off and it boiled over.

[800screws]

hey, what's up. when i had it in the jrd, it never boiled over...with the bike glowing bright red in the daytime probably means a lean jetting condition.. not sure where in the jetting though...

[matt250r21]

A few things you might want to try or think about doing. Run distilled water and some Red Line water wetter instead of 50/50 coolant antifreeze in hot temps outside. Run one or more of the large aluminum finned inline coolers that splice into the coolant hoses. Look into the Boyesen water pump cover and impellar for your YZ motor. Try to make your rad shrouds direct the max amount of air thru your rad. Check to make sure you are not jetted to lean.

If your motor has the comp bumped, are you running high enough octane fuel?

[LT250Racer609]

will the boyseen water pump make that big of a difference over stock?

[2muchquad]

compared to stock,not much,your money would be better spent elsewhere.You would be better off switching to one of those hi po radiator coolant additives like water wetter or something.