HP 25 rotary valve four stroke wring out
 

I received an HP 25 from MECOA today, it did not have an O-ring between the carb and the carb mount, it has one now. It came in a very nice box, well package for the trip. The muffler is plumbed exactly as the instructions show. The prop is a Xoar 9 x 6, it should be just about right. I'll experiment with a 10 x 5 also. The fuel will be Wildcat 2-4 10% with 18% full synthetic. The plug is a Glo-Devil 4c Special made for Saito and Enya.
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a valveless 4 stroke. just a tube with ports cut into it. very cool! only if cars were made like that, they would have less problems and be cheaper to make/buy

Jim

The ports in the brass sleeve are perfectly shaped to match the leading and trailing arc of the rotary valve port. Intake and exhaust port, that is, the glow plug port is perfectly round.

HP 25 rotary valve four stroke
Fuel===Wildcat 10% with 18% full synthetic
Plug===Glo-Devil 4 c Special for Saito and Enya
Exhaust=Stock
Prop #1=HY 9 x 6 rpm===10,300 HY, took over Bolly props.
Prop #2=Xoar 9 x 6 rpm==10,470
Prop #3=Xoar 10 x 5 rpm==9,020
Idle, so far 2,800, very nice though.That is a 14 oz tank, it took an hour to take it down to the top of the tank bracket.

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HP 25 wearing HY 9 x 6
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HP 25 with HY 9 x 6 rpm
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HP 25 with Xoar 9 x 6

I was very happy with the HP 25 numbers.


HP 25 rotary valve four stroke
Fuel===Wildcat 10% with 18% full synthetic
Plug===Glo-Devil 4 c Special for Saito and Enya
Exhaust=Stock
Prop #1=HY 9 x 6 rpm===10,300 HY, took over Bolly props.
Prop #2=Xoar 9 x 6 rpm==10,470
Prop #3=Xoar 10 x 5 rpm==9,020
Idle, so far 2,800, very nice though.That is a 14 oz tank, it took an hour to take it down to the top of the tank bracket.

HP 25 rotary valve four stroke
Fuel===Wildcat 10% with 18% full synthetic
Plug===Glo-Devil 4 c Special for Saito and Enya
Exhaust=Stock
Prop===MA 8 x 6 three blade
RPM===10,990
Idle=====2,500

This engine is quick to respond to throttle changes, there is not a hint of hesitation. It will be a very predictable flyer.

https://cimg8.ibsrv.net/gimg/www.rcu...cbf181c4c1.jpg
Master Airscrew 8 x 6 three blade.

Gary, the span across the flats is 11 mm
The pipe ID is 6 mm
The pipe OD is 8 mm
The thread OD is also 8 mm
Thanks for asking, you sent me a few pieces of .375" and .5" brass hex.

I have started construction on Eureka Models Cessna 150 20 sized with 50" wingspan.

I'll take a look at mounting the carb directly to the head and see what happens.

I was always wondering why they have the short downward manifold. I have the .49 and a .25 car engine. For break in I ran the car engine with a prop and the carb is mounted directly to the head with no manifold. It ran just fine that way. Any info on the reason for the manifold?

Max

I don't know other than to get it in a more customary position. I mounted a Saito 150 carb directly on the head, it didn't seem to make much difference other than it spit more fuel. There was no power difference at all.

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