It is a "YS 61-S"

I've had a few Ys's, including a 45, 60 and a 61, but check the pump section of this one.

Any help will be greatly appreciated.

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Heli version long stroke side exhaust. The carb is different than the aero versions and have an idle needle beside the high speed. Note that there is no regulator knob or screw in the diaphragm section.

But I'm not a heli guy and never have used one.

David

Found it!
It's a heli engine adapted for fixed wing.
Anybody has used it for a speed plane? Prop?

I don't see why u couldn't use it.

I've thought about getting a couple of them off ebay.

I got the manual. It goes up to 18,000 rpm and uses 30% nitro. It might be a speed jewel, but I will test it after the holidays. Probably a 10x10 or 10x9.

It's a short stroke!

Bore 24mm
Stroke 22mm

I guess those cases are misleading...

Apparently the new aero YS shorties will be based on a similar dimension case. It'll be interesting to see what they come up with.

David

If it's a short stroke and APC 11x7 would be my choice.

I plead ignorance on the regulator on the bottom of the case. I have the old version with the basic bellows action regulator, but have never seen this type to get my hands on him and take him apart. Any input?