Quite a few people contact me requesting advice for using 4-stroke engines in C/L applications. 

Among other things, I always stress is the importance of filtering the fuel - I use a filter on my syringe to filter the fuel BEFORE it goes in the tank and I also put a filter between the tank and carb.

Unlike a standard NVA, the 4-S carb is much more susceptible to clogging. I have unscrewed the inlet nipple of the carb found clumps of a lint-like material that would be difficult if not impossible to blow out with compressed air. I have found similar clogs in the outlet nozzle of the spigot.

The immediate sign of this type of clog is the engine's ability to draw fuel when choked but running for a few seconds before dying.

Comments???

Bob Z.

Hi, Dennis - thank you for the kind words!! I'm really pleased with the Saito engines.

I am presently flying the following 4-S setups: OS .20, OS Surpass .26 (2), SAITO .30 (3), OS .40, OS Surpass .40, Saito .56.

ALL of them have the carb locked open - I do not run any standard venturis. Why? As you heard mine run, you can understand that there is no need. I have always double filtered my fuel and have never had a problem with contaminants. The two engines that I referenced in my opening post belonged to a friend who sent them to me for troubleshooting.

BUT, there are a number of people who have experienced problems with 4-S runs, especially with the larger engines. This stems from tolerances on the barrel and bore of the carb - if they accumulate in the wrong direction, air leaks develop resulting in erratic running. THEN, you contact someone like Pat Johnston and order one of his excellent venturis and you're in business.

The Saito does not use an air-bleed setup as does the OS. The Saito has a small screw on the axis of the carb barrel. Adjusting this screw changes the distance (gap) between its end and the end of the spigot. If you look into the carb intake and turn the screw, you can see the gap change. Very simple, very effective especially in throttle response. Of course, since the barrel employs a helical drive, the gap changes with the throttle arm angle.

Regarding the "Batplane", three years ago, I mounted the engine, wired the carb wide open and after dialing in the needle, I've never touched it. Still has the original plug.

Come to think of it, I've NEVER had a plug failure in a 4-S engine.

Except for the OS .40 4-S, ALL my engines get the same fuel - Brodak 10/23, 50/50 (Also all my 2-stroke glow engines). Due to a lower compression ratio, the .40 likes a bit more nitro - I will change that soon by raising the compression a bit with a thinner gasket.

Internal modifications? NEVER!!! The guys who developed these little gems are topnotch engineers who really know what they're doing. Sure, a few ersatz engine "experts" think they can redesign the cams to improve performance - maybe they can, maybe not. I'll believe it when I see it. I have just enough experience with cam design to realize that it's way beyond my engineering capability. It's and extremely rigorous and expensive procedure.
BUT, if one of these "experts" succeeds and can prove that he/she has created a superior 4-S engine, my hat's off to them!!
I'll probably be so impressed that I'll probably buy dinner and drinks!!!!!

Bob Z.

Interesting that the Beringer's "hop up" consists of nothing more than polishing various surfaces to minimise friction.

They also make a proper bearing fit by insuring that there is no bearing bind (due to preload) when hot.

The cam they use for reverse rotation is the same profile as the stock cam.

The reason I haven't returned the article is that I have not done a complete french-to-English translation as yet.
My french connection at Bell Helicopter is pretty tied up with more important stuff.

When I come across it, I'll just send it back to you.

Bob Z.

I thought you could buy them from UltraHobby ? ?  Designed by Pat also ? ?

4-Strokes forever , kinda reminds me of when I was running Ford Flatheads, remember "Flatheads Forever" 

Over the last several months I have grown quite fond of Saito 4 strokes, own 7 of the silly things and plan to develop all future PA ships around these engines. I am completely convinced the Saito 4 stroke is the best stunt engine on the planet for under or close to $200.00.

I'm a believer in replacing the carb with a UHP-Pat Johnston manifold for a couple reasons. Consistency is the big one but they also allow me to easily modify the insert for a variable choke area. Pay attention to anything Bob Z and Brad say, although they don't completely agree on everything (setup wise) these guys know 4 strokes.

Did a test fit of the UHP Saito 56 manifold to one of my 62's this morning. It fits but could use a small spacer between the engine and manifold to make it perfect. A small piece of aluminum sheet 1/4 X 1/2 maybe 1/16 thick, with a couple holes is all that is needed. These measurements were just eyeballed so may not be exact. When I get around to actually installing the manifold I'll make a spacer and take a few pictures.

Hi Dan,

Yep the 62 was recently released.. I have two but have not yet ran either one. I expect Saito to discontinue the 56 in favor of the 62, as the 62 is only 0.2 ounces heaver than the 56.

Could be wrong but my take on why 4 strokes went in and out of favor was because most simply didn't go far enough experimenting with setups to really find the sweet spot for PA. I went through it all and almost gave up on the darn things myself. Here is a good thread from when I was playing with the 40a, it starts with my early frustrations and goes all the way to me finding the magic in that little engine.

http://www.egpworld.com/forum/default.aspx?f=2&p=1&m=19040

If you search the UHP forum for my posts "Bob Reeves" you will also find several other threads with allot of good info posted by those that helped me get to the magic formula..

I believe the bottom line is load it down with a high pitch prop and adjust the venturi (choke area) for the rpm/lap times. Four strokes simply do not work for us if they are not loaded. I see from your post Keith was running a 15-5, he is loading the engine with diameter, I run a 13-71/2, loading it with pitch and running a lower RPM. Don't know if one's better than the other but my personal feeling is with all the moving parts in a FS lower RPM is better for longevity.

I think the biggest mistake that was made by the early FS users (and the same one I made) was trying to run them with low pitch props. Once you get your brain past the idea of using a 7 pitch prop for PA you are home free.. My Score weighs 65 ounces and the 56 doesn't even know it's pulling it, haven't actually tried it but I believe it could be launched vertically and go right into a wingover.