I installed a Rand water cooled head on my 83 FL250. Still working on some other stuff on the machine and haven't ridden it yet. I'm doing this work in preparation for next Summer at the dunes. Anyway, I posted a couple pictures of my set up on this page: http://www.kartpowersports.com/honda-fl250-rand-head.htm .

I have a couple questions related to thermosiphon and water cooled heads...

1) If you can see the hose routing in my picture and you know that they are routed wrong, then please let me know.

2) If thermosiphon requires boiling to work (as I've read some say), then wouldn't adding antifreeze/coolant make the Engine run hotter?

I've seen more than one person indicate that the coolant boils and that's what makes the coolant circulate with thermosiphon. I don't know if this is true or not. I'm just repeating what I've read from others. If there is some truth to this (boiling at the hot spots on head), then it makes me wonder if running a weaker solution of coolant is a good idea. In other words, last I saw, I think a 50/50 mixture of coolant raises boiling point to around 270F. I can't remember for sure, but just throwing out the fact that Engine coolant does raise boiling point. If so, then makes me think it might be better to run with a lower ratio of coolant. Obviously, pure distilled water is another idea (with a little Redline Water Wetter to help with corrosion and assist in heat transfer), but then I've got to remember to drain the cooling system at the end of every season so it doesn't freeze.

3) Does anyone know the current draw (AMPS) that those auxiliary water pumps draw? Just curious.

Thanks,

Rhinoguy

1. Your hose arrangement is the way it should be.

2. Where did you hear the boiling comment? That is just plain ridiculous, the water flows naturally, the hot water rises to the top of the radiator and as it cools as it goes through the radiator it picks up speed (flow). The harder you push the Engine, the more heat it makes, the faster the flow.

You really don't need a pump or a fan with a 250, but neither would hurt. Your only limitation is your stator or the charge of your battery if you have an electric start kit and rely on it's battery for juice.

Thanks for the feedback Odystable. I think I read the comments about boiling in some old posts when I searched on here or possibly elsewhere when I was Googling the topic. I did read it in more than one place, and I agree that it didn't really make sense to me. If "boiling" is what makes thermosiphon work, then I'd expect that the coolant would be blowing out the overflow with the steam. So, I agree that it seemed a bit unreasonable to me, but then again I've been surprised before and learned new things. That's why I figure I'd ask. Thanks again.

Rhinoguy