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Discussion Starter · #1 · (Edited)
This is for you contrarians and radicals and other malcontents who can't leave factory products well enough alone.

A fella on another thread has told of cracking the water-cooled head on his nearly-new endure engine from a manufacturer that has gone out of business. I suggested that if replacement heads become scarce, anybody with basic machine shop skills can make new heads from aluminum billet, heads that won't crack.

As I told him, you make the new head in two pieces. The combustion chamber, squishband, and any o-ring grooves are turned into one side of your chunk of aluminum, and the water passages are milled into the other side, to be covered with a plate (your second part). I made my first one about forty years ago, for a two cylinder Konig racing outboard.

The second one I made is the one I thought might interest one or two of you here. This was a water-cooled head for an air-cooled '73 Yamaha 125 MX engine that I was converting into an outboard racemotor. Besides making the water-cooled head, I water-jacketed the cylinder as well. Having secured it, top end up, to the table of my little Taiwanese vertical milling machine, I milled off the upper four cooling fins close to the cylinder block, leaving maybe 3/8" stubs to which I welded 6061 sheet, cut and hand-formed to make the outside of the water jacketing. As you can envision, the area directly above the exhaust port took some extra care, but that got water jacketed as well (probably the most important part).

One of the first guys to do one of these motorcycle-to-outboard conversions made an interesting discovery, that it was sufficient to cool either the cylinder or the head, that it appeared not to matter which, and that you didn't have to cool both. However, first, these engines were only making about 29-30hp, and second the fuel was methanol, which has a cooling effect on the cylinder that gasoline lacks. So my inclination would be to cool both head and cylinder. Especially so for a motorcycle or kart or whatever, because the water coming out of your homemade radiator is going to be a lot warmer than the raw lake-water or river-water our outboards used for coolant.

If there is anybody at all here who has any interest in this, water-cooling some old air-cooled thing, feel free to PM me. There were several of these things done in the Seventies (incl. a Mach 3 Kawasaki) before bikes started coming water-cooled from the factory.
 

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I never thought of that... machining the the fins equal, welding a plate around the circumference of the the fins, welding an inlet and outlet coolant ports.....but on an atv , what would you use for a water pump?
Sure you can mount a small radiator, hoses, etc.
Would you use a small electric water pump (maybe an r/v ) with a battery?
Just thinking..
Joe
 

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Water coolers from www.smallenginemachineworks.com

We also did some water coolers in the 70’s
125 Yamaha


250 Odyssey with a 360 Yamaha piston / Pumper carb / Yamaha reed


:Cheers:
 

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Discussion Starter · #6 · (Edited)
I should have mentioned that one advantage of carving a new head from aluminum billet is that you can go further and make it a three-part head by having the combustion chamber as a removable insert. That allows you to make more than one such insert, with combustion chambers of different volumes, shapes, etc.. Of course, if you do this you have added to the potential for leaks that you have to seal. This feature is being done rather widely now; I wish I had thought of it when I was making my heads.

Looking at the photos, I can see that John left a whole lot more fin area exposed to water than I did. And that may well be the better way to do it for a motorcycle or kart that uses a radiator. In my case, building a raw-water-cooled, no-recirculation outboard motor, I felt that it would be easy to over-cool the engine at the cost of power, so I milled the top four fins only, and milled them down pretty short to limit surface area.

That 125 (photo) has to be a few years newer than the one I did. The first Yamaha "Reed Induction" motors had by today's standards TINY reedblocks. I had to do a good deal of carving and filling to make room for a bigger reedblock (for a floatless, barrel-valve 33mm carb that I also carved from billet) which was still smaller than what I can see would fit John's motor. Things changed and progressed pretty fast in those years.

(Maybe someday I'll force myself to learn how to do photos, although computers are such an alien technology for me that they already drive me nuts with their glitches and hiccups . . . or maybe those are MY glitches).
 

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Man, I love seeing all the cool stuff guys came up with back in the early days. It's a pretty neat lesson in history.
I remember Duncan and Trenga did some stuff for the Blasters. Quite the improvement.
 

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This is for you contrarians and radicals and other malcontents who can't leave factory products well enough alone.

A fella on another thread has told of cracking the water-cooled head on his nearly-new endure engine from a manufacturer that has gone out of business. I suggested that if replacement heads become scarce, anybody with basic machine shop skills can make new heads from aluminum billet, heads that won't crack.

As I told him, you make the new head in two pieces. The combustion chamber, squishband, and any o-ring grooves are turned into one side of your chunk of aluminum, and the water passages are milled into the other side, to be covered with a plate (your second part). I made my first one about forty years ago, for a two cylinder Konig racing outboard.

The second one I made is the one I thought might interest one or two of you here. This was a water-cooled head for an air-cooled '73 Yamaha 125 MX engine that I was converting into an outboard racemotor. Besides making the water-cooled head, I water-jacketed the cylinder as well. Having secured it, top end up, to the table of my little Taiwanese vertical milling machine, I milled off the upper four cooling fins close to the cylinder block, leaving maybe 3/8" stubs to which I welded 6061 sheet, cut and hand-formed to make the outside of the water jacketing. As you can envision, the area directly above the exhaust port took some extra care, but that got water jacketed as well (probably the most important part).

One of the first guys to do one of these motorcycle-to-outboard conversions made an interesting discovery, that it was sufficient to cool either the cylinder or the head, that it appeared not to matter which, and that you didn't have to cool both. However, first, these engines were only making about 29-30hp, and second the fuel was methanol, which has a cooling effect on the cylinder that gasoline lacks. So my inclination would be to cool both head and cylinder. Especially so for a motorcycle or kart or whatever, because the water coming out of your homemade radiator is going to be a lot warmer than the raw lake-water or river-water our outboards used for coolant.

If there is anybody at all here who has any interest in this, water-cooling some old air-cooled thing, feel free to PM me. There were several of these things done in the Seventies (incl. a Mach 3 Kawasaki) before bikes started coming water-cooled from the factory.
I had a question. I used to have a honda ellite 2 stroke air cooled and bought a pre bored head and block with over sized pistons and rings. My ruckus is liquid cooled and didn't know if I could use the block that's been bored out on the honda ruckus heads that are liquid cooled or not with out having to do any thing. I know I would have to take and reject the carb to make it run better but I just have this nice brand new motor that's been sitting at my house for ever and live my ruckus but its governed at 35 mph, won't even go past that going down hill so I was thinking of putting the bigger head on but the ruckus is 4 stroke and my motor is 2 stroke that I would like to make use to if possible. Please let me know your thoughts or if it's possible. Thank you
-Chew-
 
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