Just wondering what is the smallest commercially available 4 stroke?

Best,   DennisT

Hello Small Four strokes that are currently available (and stocked) are the Saito 40A and the H.P.21 see:
http://www.mecoa.com/hp/vt/21.htm?id=2111
Regards Gerald

We tested the OS 304S when it first came out and were very disappointed. Despite claims, we could tell no difference between it and the Surpass 26.
In my opinion, OS does not always get it right.
I've owned and flown ever OS four stroke from the 20 up to the 70, both Surpass and non-Surpass.
The .20 (non-Surpass) and .26 were very good, the 30, well, see my comment.
The Surpass 40 was the WORST 4S engine I've ever owned - JUNK in my opinion.
The Surpass 48, 52 and 70 were also fine but I had decided to stay with the smaller engines.
Regarding the non-Surpass engines, I also had the 40 and 60 - both were smooth and very quiet but not up to the performance of the competitors.

The photo shows the latest OS 30S and this was quoted by the retailer, Mainhobbies: "This item is discontinued and no longer available for purchase."

My advice: If you want a 4-Stroke engine, buy a SAITO.

Bob Z.

I have an HP 21fs somewhere. I think they run VERY well. However, the case seemed a little large for the displacement and I felt it was a little heavier than needed. But, a strong little engine.