Does your 450F MX bike overheat in the woods?

M

motometal

LIFETIME SPONSOR
Sep 3, 2001
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I think I have "the itch" again. You know, that "haven't bought a new bike for a few years" itch. I'm a die hard two stroke fan, and have never owned a four stroke MX bike but I'm thinking a 450 might be my next bike. My main concern is the overheating. I've had a couple friends that have owned Honda 450s that have had them boil over in the woods. Also I know of a KTM250SX that likes to boil over just with play riding, seems like if it doesn't have the constant airflow of track riding it gets hot.

The bike would be ridden on a mixture of track, more open trails, and tighter singletrack.

My "frame of reference" is all the two strokes I've had. The only time I've been able to overheat a CR250 (two stroke) was 1st gear, not even a walking pace on a hot summer day, for an extended period of time.

My TE610 (four stroke) has no problem between the larger radiators and fan.

What has been your experience?
 

IndyMX

Crash Test Dummy
~SPONSOR~
Jul 18, 2006
5,548
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Amo, IN
My CRF450 over heats on the track.. but lately the temps have been pretty high, so I'm not real concerned with it.

In the woods, most definitely it'll over heat.
 

Patman

Pantless Wonder
LIFETIME SPONSOR
Dec 26, 1999
19,765
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My 4 stroke NEVER boils over.
 
M

motometal

LIFETIME SPONSOR
Sep 3, 2001
2,680
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Patman said:
My 4 stroke NEVER boils over.
Click to expand...

Pat, my friend! How have you been?

Your Honda doesn't count! It's air cooled, right? Just like my hot rodded 650, since it's pretty tough to "boil over" the oil they don't really seem to have a problem. I suspect there are components that have to be run at a looser tolerance (maybe piston clearance etc.) to account for this. Since the oil runs through the frame, and of course those monstrous cases, there's a lot of surface area there to act as a big radiator and conduct heat away elsewhere. I always figured the air cooled engines were tough on the oil and tried to change it a bit more often, especially in hot weather.
 
J

jb_dallas

Member
Feb 17, 2009
498
0
Until April, I rode a YZ400 MX bike on trails and it would consistently overheat in the tight woods. I bought a higher psi radiator cap and a trail tech computer that gives engine temp. I would monitor the temp closely. It worked ok, but the gearing of the YZ was all wrong, so I sold it and bought a WR426. It has a spill over tank that catches any coolant that flows past the cap. I kept the computer and I never overheated the WR. The correct gearing also helps. For a bike without a tank, buy a higher pressure radiator cap to keep the coolant where it belongs. You can also rig a custom spill over tank with a baby bottle and some hose...very simple. Personally, I love the computer...there is never any doubt if the bike is hot.
 
M

Matt90GT

Member
May 3, 2002
1,517
1
The bikes have to have air moving past the radiators to cool them. If they dont have that, they will overheat. Period.
 
J

jb_dallas

Member
Feb 17, 2009
498
0
I agree that a bike must have air flow. However, as described above, there are other tricks that can be done to help with the overheating and monitor the engine temp.
 
R

rmc_olderthandirt

~SPONSOR~
Apr 18, 2006
1,533
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I belong to an enduro club in California, and every month from October through June we have a "club outing" were we put on and ride an enduro in the desert. They are shorter than the district enduros and there are a few other cost and time saving differences but difficulty wise they are right up there with district versions. A major difference is that when we are done we all have to pull ribbon.

Most of the bikes are 450 for strokes. I have never seen anyone have overheating issues while racing, but pulling ribbon at the end is an entirely different story! When pulling ribbon we end up "leap frogging", the person in front stopping at a ribbon to untie/rip off while the people behind them continue on to the next ribbon. The result is that we are riding fairly slow and stopping a lot. The four strokes that don't have electric fans are often overheating (especially in the warmer months) while the two strokes don't seem to be bothered by it.

A fair number of the club members have electric cooling fans to deal with this.

Rod
 
P

pcoakle1

Member
Apr 14, 2010
4
0
My '02 CRF450 would boil over a little if I was riding slow for long periods of time in woods. But it was never a problem and once bike cooled down after riding all day I would only need to put in a couple ounces of coolant to make up for the loss, so in my opinion it wasn't a big deal. I owned that bike till last year with no mechanical problems.

My '09 yz450f seems fine too.

If you are going from a YZ/CR 250, then you'll probably be better with a 450.
I have ridden both and generally prefer the 4 strokes. But keep your 250 for when you get the itch for that bike's power band.
 
B

brentn

Member
Aug 7, 2009
42
0
I ride woods pretty hard where I live. My bike is a 2010 yz450f and I have not once had the bike overheat on me in the sticks with 10 hours of ride time on it. All I do is woods riding and sometimes it gets very technical with lots of clutch slipping. Since the oil for the crank and the gearbox is shared you'd think that clutch slipping combined with the slow speed of the technical areas you would overheat for sure. But I don't.

The rads need airflow and if your jetting is not to lean I don't think that your going to have a problem even at about 5kmph of riding technical. At least I don't.
RPM's are kept low on the techincal btw.
 
D

dirtbikerida63

Member
Apr 7, 2008
61
0
i have a 2009 kx450 and when im riding in tight woods (1st gear, lots of clutch use) i can feel the bike between my legs and my seat get hot but havent had any problems with it.
 

Patman

Pantless Wonder
LIFETIME SPONSOR
Dec 26, 1999
19,765
1
motometal said:
Pat, my friend! How have you been?

Your Honda doesn't count! It's air cooled, right?
Click to expand...

Been good, just a little slow getting back to this thread. ;)

Air & Amsoil cooled :fft:
 
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