I have a CRF250 and on the left rad the coolant hoses runs nearly all the way down the back of the radiator, as i'm sure also happens on most 4 strokes. I was wondering what effect replacing the straight part of the hose with aluminium pipe would have on the cooling? Obviosly i would like to improve the cooling and was wondering if this would help? My only theory on this is that i would have thought aluminium disipates heat better and if the pipe is behind the rad the air would flow over it.

In theory it sounds like it could help. I have two concerns.

1. Rock Damage. Not sure what kind of riding you do, but in the Arizona desert rocks destroy everything.

2. 3 inches of tube doesn’t offer a lot of surface area for cooling. You could make fins to increase the surface area but that leads me back to the rock damage problem.

I’m not trying to rain on your idea. I hope you do it and I’d really like to know how it works. :ride:

Yes, I also thought about fins but it depends if it will actually help first as it would be a lot of cutting and welding as i dont have a lathe. The pipe i was thinkin of runs behind the rad so it should be protected by the rad or the radiator scoop side panel. If I had a temperature gun I would try it, was just wondering if anyone else had tried it or knows from experience that it would definately help the cooling.

Not much cooling would occur. Only the fluid immediately in contact with the wall of the tube would be cooled, and that would only be cooled very slightly b/c the surface area of the tube is so small. They sell little inline coolers with fins on them that are just like what you are talking about, but they still don't do much. The tubes are just too big around for how much surface area is open to the air, this is why your radiator uses a series of very skinny tubes.

To expand on KJ's comment. Think about how much coolant in in your entire bike. Not even a quart in most cases, not a lot. Now look at the amount of surface area on your radiator. Look at those thin tubes with all the fins. Just a teasoon of coolant and all the tubular surface area.

Some transmission coolers have fins inside the tubes to increase the inner surface area you could put ribs on the inside and outside. All you would need is an aluminum tube and some 1/8 " bar /tube and have them heliarc welded to the inside and outside just leave room to clamp your hose on. Do it then let us know.

Biddyboo said:

Fins on the outside are what is really needed. Fins on the inside will make little to no difference because convective heat transfer from water to aluminum is much better than from aluminum to air. The amount of heat transferred from the aluminum to the air is the limiting factor in any liquid to air heat exchanger. Even with fins however, the surface area will still be very small compared to the volume of water in the tube. Add to that the fact that the air passing by is already slightly warmed by the radiator directly in front of it and you lose even more of the potential cooling capacity.

Ive seen inline aluminum oil coolers on pitbikes and they look exactly like what you are describing. It will help with cooling but I can't tell you how much. Aside from being able to get enough surface area, you also have to cause turbulence of the coolant (slow it down inside the hose/cooler) so that it will have enough time to cool down.

i used aluminum tubing for all the straight sections on my ministock race car just the bends are "goodyear wet exhaust tubing" I did this after we discovered my friends pile of junk race car was sucking the universal flexhose shut

Here it is: http://www.rockymoun...96&stockId=3165

I used one on my CR167. Have no idea how much it helped, but it got very hot and obviously dispersed some heat.

I would think Fluidine radiators would be far more effective, and expensive!

What if rather than one large tube you used several small tubes with fins. if you have room.

Increasing the volume of coolant in the system should have a bigger effect on cooling than installing an aluminium tube in the hose. The outside air temp would have to be very low to transfer enough heat for the surface area size the pipe will have to make a great difference and even then if the air temp was that low I would guess that you would have no probs with cooling as the radiator should handle it.

A larger radiator or an extra reservoir will have a bigger effect on cooling but it will also affect the handling of the bike by making it heavier. This is a trade off you would have to make depending on which issue is the bigger of the 2.

I have always thought it would be cool if all or part of the frame could be used for coolant fluid. It would balance the extra weight better and have a larger surface area than a straight reservoir allowing extra cooling (this extra cooling would still be negligible with the biggest gain being weight balance)

henryboyle said:

In other words, what if you added another radiator? :lol:

stunnah said:

I have a hard enough time avoiding the one hot exhaust pipe when loading the bike. Cool idea but recipe for disaster.

I found this link on another thread. Seems to answer the original question.
http://www.rockymoun...dFamilyId=23919

In my experience, the most important factor in bike cooling is proper jetting. Too lean runs really hot. Counter-intuitively, the fuel provides a lot of cooling (before ignition).

Yes those inline water coolers would fit great, but if it was behind the radiator it could be probably 200-250 mm long. I think it would be expensive and a lot of effort to make one that long tho. Probably would be better off getting oversize rads and maybe a different water pump. Those water pumps also make me wonder if they actually work. I'm also going to put some reflective foil on the pipe that runs near the exhaust, I dont know how good the heat reflection will work but i know that pipe gets very hot

I used my right side frame for a overflow tank and have not lost any fluid sense. I used to have to add fluid after every ride.