DG Water Cooled Head for 81-84 ATC 250R

[christph]

I thought you guys might like to see a rare piece of 3-wheeler history. This is a DG water cooled head for the 1st and 2nd generation ATC 250R. The coolant circulates using the thermosiphoning effect. Hot water is less dense so it rises to the top of the radiator, while the cooler water at the base of the radiator flows down to the head. I was worried the circulation wouldn’t be very efficient but after running it, one hose is clearly a lot hotter than the other. It’s a high compression head like the DG gold head, so I think it will run best on some ratio of race and pump gas. I haven’t had a chance to take it out for a real ride yet, but so far I’m very impressed with how much grunt it gives the R. Plus it just looks cool as hell. I love rare old school parts.

[yaegerb]

That is a very neat piece. Where did you find that?

[HondaRidr]

super cool!!

Sent from my SM-G930T using Tapatalk

[xrider]

Nice. Is that the NOS one that Mario was selling? Very cool piece.

[3 Wheel Drive]

So that’s where Barn got the idea of mounting the radiator on the 1st Gen T3?

[atc300r]

This is a cool piece.Iv only seen a few of these pop up for sale.I have the aircooled version.I had thoughts of getting a fl 350 odyssey liquid cooled head and putting it on my 300r.

[barnett468]

So that’s where Barn got the idea of mounting the radiator on the 1st Gen T3?

But ours has a headlight...at least until you crash!


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR AND THE ONLY PERSON ON 3WW WITHOUT AN EDIT BUTTON OR A STAR

[El Camexican]

I remember seeing a write up on that head when I was about 14 years old and thinking that I could somehow incorporate something like it to my YZ 80 by soldering sheet metal around my air cooled head and plumbing it up to a old heater core that my dad had in the garage that probably had a leak.

I now realize the result would have been an otherwise perfectly good YZ 80 being sold to a scrapyard.

That’s the same system one of the Franks Rotax trikes used, but I don’t know if that was Frank’s design, or if Rotax built that head.

[christph]

That is a very neat piece. Where did you find that?

It showed up on ebay a few weeks ago--see xrider's comment about Mario. It was quite a bit of coin but I figured I'd never see another NOS DG water cooled head again, so I bit the bullet. I did the same thing with the Westcoast swingarm, which you never see for the 2nd generation. I bought it 4 years before I bought the machine. I knew I'd get a 2nd generation R someday, so I snagged it on ebay when I had the chance.

[christph]

This is a cool piece.Iv only seen a few of these pop up for sale.I have the aircooled version.I had thoughts of getting a fl 350 odyssey liquid cooled head and putting it on my 300r.

Here's a water cooled head for the FL 250 and it seems like I've seen them for 350's too (see link). It looks like there might be fitment issues with the bolt pattern and combustion dome (for a 300), but it looks like a good starting point for a machinist willing to make some modifications or start from scratch.

https://www.ebay.com/itm/HONDA-ODYSS...1Yq49y&vxp=mtr

[Aulbaugh]

That is very cool! I haven't seen that before , thanks for sharing the sweet pictures!

[atc300r]

The 350 odyssey has the same seven bolt pattern as the 300r.

[christph]

The 350 odyssey has the same seven bolt pattern as the 300r.

Yeah, but I don't think it would be a direct bolt on. What about the combustion camber? I'm thinking issues like diameter and dome volume would create problems.

[christph]

I finally got to take the 84 out this weekend and test the DG water cooled head. Damn, this thing hauls the mail--I'm still grinning from ear to ear. Compared to the DG gold head, it revs out a lot harder. I'm not sure what explains it. The next time I have it apart I'm going to compare the domes. It could just be the cooler engine temps. With the gold head I had to run higher octane (97) to prevent detonation, and the water cooled head is running stronger on 91 octane pump gas, with no sign of heat fade. Somewhere on 3WW Mike Coe said his 2nd generation R with the water cooled head was one of his fastest machines. I believe it. If you find one for sale snag it, you won't be disappointed. They occasionally show up on ebay. I'm also thinking about making parts for a few machines. I might trying reproducing it.

[barnett468]

I finally got to take the 84 out this weekend and test the DG water cooled head. Damn, this thing hauls the mail--I'm still grinning from ear to ear. Compared to the DG gold head, it revs out a lot harder. I'm not sure what explains it. The next time I have it apart I'm going to compare the domes. It could just be the cooler engine temps. With the gold head I had to run higher octane (97) to prevent detonation, and the water cooled head is running stronger on 91 octane pump gas, with no sign of heat fade. Somewhere on 3WW Mike Coe said his 2nd generation R with the water cooled head was one of his fastest machines. I believe it. If you find one for sale snag it, you won't be disappointed. They occasionally show up on ebay. I'm also thinking about making parts for a few machines. I might trying reproducing it.

Depending on how your gasoline is formulated over there, it is quite possible that at least part of the difference is due to the gas itself, because, in the US at least, it used to be made so the higher the octane rating it had, the slower it burned, and this slower burning can reduce hp. Fuels are very complicate and I don't know nearly as much about them as I do about O I L!

Of course, it there is a difference in the volume of the head, the power will also be different because the compression will be different.


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR AND THE ONLY PERSON ON 3WW WITHOUT AN EDIT BUTTON OR A STAR