kawrider240

Member
Apr 29, 2003
8
0
i have a 93 kdx 240 (200 with the big bore kit) and last weekend riding the thing just guzzeled water had to carry bottles and refill rads about every 30 minutes. have never had a over heating problem rads are good head gasket was perfect exhust was clean no coolant burning. top end rebuild 30 minutes of riding hard coolant gone air temp was about 75 and humidity 60% any ideas
 

dirt bike dave

Sponsoring Member
May 3, 2000
5,349
3
Were you riding deep sand or mud?

Lots of hill climbs?

How long have you had the 240 kit in?

Any chance your jetting is a little too lean?

Are you running 50/50 water and anti-freeze?

An especially brutal trail and a hot or humid day can really cause the overheating, so it might just be a one time thing.

For example, I had a '99 CRE 250 Honda for several years, and that thing never used a drop of coolant. Except on one ride where I lost about 3 pints in 10 miles of hell.

High humidity can hurt the radiator's ability to transfer heat, but temp of only 75 is pretty moderate.

FWIW, lugging the motor and riding at low rpm will generate more combustion heat than revving it out. I had a 240 kit in my old '84 (air cooled) and that thing was like a 500 off idle.

Basically, if you are riding a gear high and chugging, that can contribute to the overheating issues. A lower % of anti-freeze in the mix might help transfer the heat a little better.
 

kawrider240

Member
Apr 29, 2003
8
0
no extreme conditions good midwest rides 30 seconds full throttle up hill but same trails never had this prob same jetting run 108 oct. run royal purple 30/70 thanks for the reply any other ideas im stuck. water (just plain water ) flows like mad through the engine im stumped
 

sr5bidder

Member
Oct 27, 2008
1,463
0
when you filled the radiators did you take out the small bolt on the left side radiator to vent air as you filled?

Does your model have a overflow tube/catch tank?

to check flow fill radiators beg borrow or steal a heat sensor gun and start and let idle you r radiators should warm up within 3-4 minutes, if not check the waterpump, then the passage from the head to the water pump (base gasket allowing flow?)

I'd start it up and see where the water is going too ( out the cap, waterpump area, hoses) get a dye from the parts store and a black light.

its either leaking or burning

I take it you just rebuilt the top end, is the 240 new?
 

mudpack

Member
Nov 13, 2008
637
0
dirt bike dave said:
High humidity can hurt the radiator's ability to transfer heat, but temp of only 75 is pretty moderate.
While high humidity can hurt a human's ability to lose heat, unlike you and I a bike's radiator does not depend upon evaporation to lose BTU's . Relative humidity will not affect a radiator.
The rest of your post was spot-on. :cool:
 

kawrider240

Member
Apr 29, 2003
8
0
no extreme conditions good midwest rides 30 seconds full throttle up hill but same trails never had this prob same jetting run 108 oct. run royal purple 30/70. kit has been in for about 3 years. the bike screams runs great but after a while i can feel the air going through the rads stop being hot and i have no idea where the water is going even the over flow is dry but if its sitting there i cant get a overflow.
thanks for the reply any other ideas im stuck
 

glad2ride

Member
Jul 4, 2005
1,071
1
Is your transmission oil a milky gray? KDX's of that time frame sometimes have the seals wear, allowing it to leak. The bearing may be worn or the gear also.
 

jason33

Member
Oct 21, 2006
655
0
water just water??? ( its turning to steam), go with a cool anti freeze, my over bore kx used a lil water now n then ,but not like that
you got the head gasket on right (right) hahaha if on wrong it will block water holes i do believe, then no flow, or flow not worth a crap, keep us posted , good luck
 
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