The more I read the more I change my mind, I swear, what a pain buying a new quad can be. I was really looking at an LT250R but am starting to wonder how parts availability is going to be in the coming years. I know the 400EX has a huge aftermarket but I wonder about its ability to stay cool. I live about 45mins from Glamis in Yuma Arizona. Its very hot here, over 100 for at least 4.5 months out of the year. Will the 400EX's air/oil cooling be sufficient for this climate? This is a major concern for me. Thanks for any help.

 

Well naturaly all aircooled engine overheat but you would be able to ride for an hour but what i would do is ride for an hour and shut it off for 10 minutes then go riding!.



Nasty

 

I know of a guy who POUNDED his 400EX at glamis/pismo for two years. Hit the rev limiter constantly, in the heat of glamis and the cool of Pismo beach, the bike never EVER gave him problems. He says it is the hardest working bike hes ever ridden.

Ive never ridden mine in the dunes, but I have had it running constantly for long periods of time. Me and my GF rode double to a river once, 45 minute ride each way in the AZ heat. No problem at all for it. Never have any problems with it at all.

 

Well, I dont ride for more than an hour at a time but all air cooled engines dont overheat either. I dont mind taking a break here and there but if its going to oftern that bothers me. What are your experiences with the 400EX's?

 

that is not true ALL air cooled machines do over heat at some point the 400ex runs hot regardless of wether you ride it in arizona or not if you dont beat on your quad than you will be fine matter of fact is that even liquid cooled engines ove heat sometimes it all depends on how u ride

 

madweazel i have had my experiences with overheated banshees overheated blasters and overheated outboards so trust me every engine will overheat....i currently own a 2002 400ex with a IMS bigbore kit so its a 440 whitebros r4, whitebros rev. box,fourstroke tech cam,dg bumber,dgnerfs,renthal,k&K easy change side cover,and the list goes on.... thats my experence with 400exs

 

YellowIMS440ex -

I'm curious, how does a free-air overheat? Isn't the term "overheat" related to a liquid cooled motor (i.e., when coolant boils out)?

When a liquid cooled motor overheats, one must stop operating the engine, or else metal to metal contact could occur - given the coolant is basically it's only means of external cooling (fuel being it's internal means of cooling).

Describe the symptoms of a free-air overheating.

Madweazl - you really don't need to worry too much about the 400ex engine running overly hot. Thousands of folks have run this engine in hot climates without problem. If I were in your position, I would only make sure you run a heavier oil (15w-50 or 20w-50). Also, you may want to increase the main jet one size (to a 150). This will allow the engine to stay a bit cooler. No worries about increasing the main one size, honda runs them really lean from the factory. I wouldn't think you would see any open throttle skipping from a 150 main jet.

ogre

 

How does a free air engine overheat? easly when u beat the **** out of the engine it over heats and if a overheated engine only applies to liquid cooled engines and radatiors boiling over dont ya think it would have a diffrent name..... all engines will over heat at one point of abuse. lets take the blaster for instance after about 2 hours of hard riding the aircooling pretty much stops help cool down the engine and the power is sluggish choppy this is what we aircooled riders call overheating....




Nasty

 

Well, I disagree about all engines overheating as my Mojave has never overheated since '91 when it was purchased. This is all besides the point though.

I think I will go for the 400EX just because it has such a large aftermarket right now. The dealer up here had a '99 for $4000 I think, is this a fair price? It looked like it was in pretty good condition. There was also an '00 for about $4200 I think. Were there any differences between the the two (they were both the same color so dont start that crap again!)? What are some week points on this chassis that I should look for when making a purchase?

 

YellowIMS440ex -

Don't you think the term "overheating" is a bit general, when used to describe free-airs?

The only thing really that can get overheated is the oil. Overheating the oil will cause the oil to break down. Symtoms could include ring blow-by, thus causing oil consumption. In the worst case, metal to metal contact. Would that be considered overheating? Because this can be corrected with a heavier weight oil (under normal circumstances).

What I feel is really happening, given your blaster experience, is the following: Running your engine hard for 2 hours is more than enough time to get it to normal operating temps. These temps stablize long before 2 hours (like 1/2 hour into riding, at most). Then, as you continue to ride, the heat (constant temp) slowly dissipates into adjacent parts - most importantly, your carburetor. This, in turn, heats the air that is entering the carb. Everyone knows that as air gets hotter, it expands and gets less dense. Thus, less oxygen molecules per unit of air. Less oxygen means a richer air/fuel mixture. And that is why perforance is lost, because now you have a machine that is running too rich (just barely).

That is why you must choke an engine on a cold day (exact opposite). Until the engine has enough time to warm up in order to heat the air coming into the carb, you have a lean condition. The air is too cold, and thus too dense, for your jetting.

I do know what you're talking about though, as I too own a free-air. It's not overheating though, it's a carburetion issue dealing with heat. Sure, I could switch the main jet in the carb when it did this, but by the time I did it, the dang thing would be cooled down!

madweazl -

I would avoid the '99, as some have said the swingarm was a bit weak that year (I have no personal experience with that year, however). Overall, in checking over any quad, lift it up onto it's rear grab bar, and inspect the frame and swingarm for cracks. Check airbox for oil (possible blow-by). Look for general signs of abuse (bad plastic, unusual tire wear, handlebar ends, rims, etc.).

ogre