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Is HKS 700E Engine a decent light weight 4 cycle Rotax alternative?


http://www.hks-power.co.jp/hks_aviation/products/700e/index.html

Does anyone have any comments about the Japanese HKS 700E engine? They are really light weight, 4 cycle engines, 60 HP, and weigh less than a Rotax 912. The HKS 700 Turbo version by the way has been discontinued.

There are situations where even a 912 weighs too much, and a person would like to avoid a 2 cycle if possible. Case in point, the recently announced single seater Merlin PSA model from a company called Aeromarine-LSA. This all metal single seat “mini-Cessna 150” has a gross weight of about 715 pounds. It come in Taildragger and Amphib versions as well. One power option is a 2 cycle Rotax 582. Also mentioned are a future Pegasus 0-100 60HP 4 cycle engine, and an electric motor option. Since the last two are not currently widely available or proven, the discussion focuses on other 4 cycle alternatives. Chip Erwin, whose company sells the Merlin PSA, has told me the Rotax 912 is too heavy re weight and balance for the single seat Merlin.

http://aeromarine-lsa.com/merlin-psa/


Again, enter the HKS 700E engine. 60 HP, 2 ¼ gallons per hour, 11.3:1 compression.

Estimated installed weight for various engines:

Rotax 582: 64 HP 110 pounds**, 2 cycle
Add:
• Oil Tank = 4.375 lbs
• Oil (5 pint) = 6 lbs
• Coolant, (.75 gal) = 4.4 lbs
• Coolant Lines = 3 lb est
Total 125.775 Lbs

Rotax 912: 80 HP 132 pounds+ ~ 20 lbs more, 4 cycle Total ca. 140-150 lbs

HKS 700E: 60 HP 108 pounds** 4 cycle
Add:
• Exhaust System = 6 lbs
• Oil Cooler and Tank = 5.25 lbs
• Oil = 7 lb
Total 126.25lbs

715 lb Merlin PSA with a 60 HP HKS 700E engine gives 11.9 lbs/HP which is not too shabby.

Feedback on the HKS 700E series would be welcomed.

Disclaimer. I don't own one, but I do know several people who do. The HKS is a very good little engine.

However, it is in no way comparable or interchangeable with a 912 Rotax. Concerning usable power it is more comparable to a Rotax 503. (The Rotax 582, at 65 hp, is far more powerful when compared.)

This is from a friend who converted from a 503 to a 582 then to an HKS on his Flight Star: Performance dropped to comparable with the 503, after moving from the 582, but with an incredible 2.5 GPH fuel burn.

The near exact story came from another buddy with a Challenger II who went through the same progression of engines. Neither of them want to go back to the 2-strokes even with the performance loss. The benefits of the 4-stroke: reliability, clean running and low fuel burn far outweigh the performance loss.


All that being said, it is a very nice running, well engineered engine.

Similar response that Av8r has given, I have a friend that installed one in his Kitfox. Haven't spoken to him in a while but he is an old ag-pilot. When I conversed with him on the HKS, he seemed very happy with it. He also wasn't a big fan of the 2-stroke motors. No complaints about performance since he strictly flies the KF solo.
Now that you have posed this question, I need to call him and see how life is going...