The first model of the .61 had a bell type rear rotary valve and Schnuerle porting design, both were unheard features of in the 1960's.

These used an odd prop bolt with the spinner nut being part of the stud. The spinner nut was actually cast onto the stud.


Soon the .61 evolved into a front intake version which proved to be more suitable for conventional model airplanes. The first versions were made from the rear intake case by machining off the front and using a bar stock, screw in back cover with a new cast front intake housing.

This placed the exhaust port on the left like most modern engines.

A new run of castings were made after modifying the mold for a more conventional back cover.

They also made a blue fin version.

With the screw bosses added to the crankcase a new rear intake version was made. Unlike the original, this one used a disk valve.

Very few parts are available for the first HP .61 (pre 1972)
with four head bolts and rectangular exhaust flange.

A few parts interchange from the Silver Star .61.

The following #’s interchange on some of the 4 bolt engines:
14-2201, 15-2201, 26-2201, and 16-2201.

If you need one of these 4 parts call first.
Tel. 626-359-6972



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