So how does the K77 compare to your PA75 weight wise, about the same ?
It was originally advertised by Kaz MInato who was instrumental in getting them built, as weighing .5 oz less that the PA 75. However on my scale mine weighs .41 oz less than my PA75. Close enough I guess but not really any serious consideration in my book
I would add that while I haven't flown mine yet it is slated for and installed in and airplane that is about two or three weeks away from flying.
I have run it on the bench through about 8 6oz tanks of fuel. Actually it ran very steady from the first run on 15% nitro (remember I live in Tucson AZ and it was hot), with 20% half castor and half Klotz. It is an easy starter, needles easily and runs with authority on a 13-5 APC prop. I also ran it with a 13-5 three blade Medjlik carbon prop and it turned it the same RPM at nearly the same needle setting as the 13-5 APC. 9600 RPM in a medium fast 4 cycle. I believe it really didn't need very much breakin because it ran very steady and the needle setting required only a tweak during the first run only to maintain the same RPM till the tank ran dry. Actually the first two runs were accomplished in three minute cycles of running and then cooling but the fit of this engine appears to be so good that it really seemed unnecessary. I did it anyway.
The last 2 6 oz runs were accomplished with a Randy Smith PA75 pipe and the engine handled the pipe very well at nearly the same RPM. I didn't try to adjust the pipe setting to be ideal because that will change a bit in the air as the engine unloads a bit.. I used a pipe length of 18.25 inches and it ran good. RPM didn't change appreciably from beginning to end of tank. No pipe pressure which I probably will install and use when installed in the airplane.
The first runs were accomplished using the muffler supplied with the engine (extra cost) and although it ran and handled very well and was very quiet it seemed to be a bit more powerful and smoother on the pipe but that's really only opinion as none of the visible factors etc really changed significantly (except the noise of course the pipe was significantly louder according to my neighbor). Oh yeah, it ran for 6 min 40 seconds on the muffler with 6 oz of fuel and 6 minutes 10 seconds on the pipe at a slightly richer (only a small tweak on the needle), on the same tank!
In my opinion this engine may be the equal of the PA75 (actually that's what it was designed to be according to Kaz). I think that in itself is a great recommendation because in my opinion the PA65 and PA75 come very close to being perfect.
My PA75 does use a bit more fuel but it also has a larger venturi.
Oh yeah, It's also Very Purty !
Randy Cuberly
PS: It uses the same header pipe as the PA75 and can be mounted in the same mounting holes!
Topic: New 77 Stunt engine (Read 3158 times)