Hi Steve, I have never run a 4 stroke but have been around alot of people who have and they seem to love them, on the other hand people love their 2 stroke also.My point is that both work well when set up correctly. Both have advantages and disadvantages. May I suggest to find an engine that is EASY to set up and use it. A flip and fly engine if you will, you will be alot happier if you dont have to fiddle around with them.

Steve - what Jim wrote holds very true.
Many people, myself included, are very happy with the performance of the 4-stroke engines.
Others have tried them and just prefer the 2 stroke.

I have personally tried just about every brand of 4S engine on the market, reaching a conclusion there there are only three that seem to work extremely well for C/L:
ENYA, OS and SAITO.

If you want to stay small, the Surpass .26 is a fine little engine but, in my opinion, the SAITO .30 is the absolute winner in this size range. I have used it to power many .35 size planes - Nobler, Argus and the like.
I even flew my profile ARF Cardinal with it (a bit of a chore but it was fun). One now resides in my Argus and at around 42 ounces, the plane flies a lot better than I ever will.

If the .40 is your preference, the SAITO .40 and Surpass .40 are both excellent, the SAITO being a bit more user friendly for C/L, the OS a bit more powerful.

Next step up is the .46 size. There are three in this area: Surpass .48, ENYA .46 and SAITO .45. All sadly out of production. The ENYA .46 is the most amazing of the three. I truly believe it to be the most powerful of any engine - 2S or 4S in its size range. We've used it to replace a Super Tiger .46 and a Double Star .51 and there was no comparison. The OS .48 is just behind it, with excellent power. The weakest of the three is the SAITO .45. Silky smooth sport engine but down on power. It was replaced by the .50, which works very well.

In the mid-50s range, you have the ENYA .53, the Surpass .52 and the SAITO .56 - ALL EXCELLENT choices, in my opinion. In two cases, I acquired planes formally powered by the ST .60 and installed the ENYA .53. Both planes were in the 80 ounce range and the original builders, both top level flyers, agreed that the planes flew better with the ENYA. A friend of mine replaced a piped .61 with the OS .52 and was more pleased with its performance.

In the .70 - .72 area, we'll need feedback from others - my experience with them is minimal.

A word of advice - a few people I know purchased other brands of 4S engines. While fine for RC, they were very disappointed in the C/L performance.

Bob Z.

I think one of the biggest misconceptions is classifying 2 strokes as "rpm oriented" and 4 strokes as "stump pullers".  It's not that simple. There are simply too many different engines out there to make those assumptions anymore.  The Yatsenko Discovery Retro LS 2 stroke is an acknowledge torquer, while the hot cam Saito 72 4 stroke is an acknowledged spinner, (it is).

You simply have to take it motor by motor and find out how that particular engine was designed to run.  The Saito 40A, (which I also own) is a straight up house puller!!! In terms of torque, it makes my Saito 72 look like a girly man.

The Moki 61 long stroke which is still being made, may be one the strongest 61's ever made in terms of torque. The Thunder Tiger 40 pro b.b. has a well deserved reputation as a very high rpm engine out of the box and is popular in sport class Quickie 500 pylon racing. I saw a bunch of these motors last weekend at the NMPRA races here in socal. The guy I was talking too told me he was getting 17,500 out of the box and one of his competitors was getting 16,800, also out of the box. Very small props running at very high rpm's-classic spinner.

The OS Max LA 40 stunt which has now been discontinued, always seemed like a spinner to me. It's 46 cousin seems like a classic torquer. I have put A LOT of flights on both these motors.

In summation you have to take it motor by motor.

  Thanks everyone for the comments. since this build is down the list a ways ,I have time to consider my choices.
THANKS
Steve