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Sep 09, 2019, 08:37 PM
KC4JAJ
Jim Johns's Avatar
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Discussion

YS 61 Long Stroke RPM


I just acquired a nice YS 61FS today. Can anyone tell me the preferred RPM range for this engine? I seem to remember that the OS 61SF/RF preferred 11,000-11,500 or so.

Thanks in advance.
Jim
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Sep 09, 2019, 11:33 PM
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I think it should be around 10,000-10,500 with a 12x10. I have the AR and it goes 10,000 with a 12x12.
Sep 10, 2019, 06:20 AM
DavidsPlanes
doxilia's Avatar
Jim,

Is that a round head (60FS/FR), square cast head (61S/R) or square machined head (61AS/AR) engine?

The round heads were short strokes whereas the square heads were long strokes. SS were 14-15K RPM engines on suitable props (11x8-11x10)) whereas the LS were “Hanno like” engines which could turn 9.5-11.5 RPM again on suitable props (12x8-12x12-13x10). For the round head engines you can essentially use the current “classic” cast square head engine instructions as they are SS engines built into a LS case. Different internals obviously.

David
Last edited by doxilia; Sep 10, 2019 at 06:27 AM.
Sep 10, 2019, 06:58 AM
Registered User
Jim: I just flew my Dash 5 yesterday with a YS 61 on YS 20/20 fuel with a pipe length at around 17" and an APC 12x8 and got 12,200 on the ground. Bill
Sep 10, 2019, 09:13 AM
Registered User
Quote:
Originally Posted by bkanter
Jim: I just flew my Dash 5 yesterday with a YS 61 on YS 20/20 fuel with a pipe length at around 17" and an APC 12x8 and got 12,200 on the ground. Bill
How did you find the flying characteristics of the Dash 5?

Had one many years ago but wing joiner failed.
Sep 10, 2019, 11:03 AM
KC4JAJ
Jim Johns's Avatar
Thread OP
Quote:
Originally Posted by doxilia
Jim,

Is that a round head (60FS/FR), square cast head (61S/R) or square machined head (61AS/AR) engine?

The round heads were short strokes whereas the square heads were long strokes. SS were 14-15K RPM engines on suitable props (11x8-11x10)) whereas the LS were “Hanno like” engines which could turn 9.5-11.5 RPM again on suitable props (12x8-12x12-13x10). For the round head engines you can essentially use the current “classic” cast square head engine instructions as they are SS engines built into a LS case. Different internals obviously.

David
Thanks everyone for the help. bkanter, that detailed info is really helpful.

I'm aware there are several versions - I now own at least one of each version except for the Classic. Let's see - three 60FS, one 60FR, one 61FS, one 61AR and a 45FS. This new one is a 61FS - side exhaust non-AR long stroke. The last regular LS I owned was a VERY EARLY model that I pitched in the trash after it POed me off one too many times and replaced with an OS 61RF-P.

Jim
Sep 10, 2019, 01:14 PM
Registered User
Jim I have an OS 61RF - P in my Atlanta and it is a great engine. Good luck. Bill
Sep 11, 2019, 12:35 PM
Registered User
I check mine Classic 61 Ys yesterday the short stroke. 13,400 rpms on the ground with a 11x9 APC prop. Cool power 15%.


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