Martin: I have a bunch of SAITO 30s but I’ve never seen or heard of a 30 SH.
Bob Z.

They also made a “knight “ series.
Black case, gold rocker covers.

Hi Martin, I came across some more info this morning.

I picked up a new Saito FA-40a and was reading thru the owner's manual. The manual is a generic one that covers Saito engines 30-125 sizes.

The manual specifically calls out the FA-30S(H) and different instructions for setting the low-speed needle on the 'air bleed' type carb.

So, it sounds to me like the H engine uses a different type of carb compared to the other engines covered in the manual. Maybe that's what the H designation means. Just a different carb setup?

Interesting find my friend

Now the question is what is different about the carb, if it has a larger intake opening it will deliver more power!

Do you guys run the Saito 30 with the rc carb lock or with a custom made venturi? 

I  have a Nobler ARF collecting dust here and I am thinking  to built it and use Saito 30 just for fun.


Martin

I don't believe there is a difference in the carb opening size. The low speed (idle speed) adjustment on an air-bleed type carb is different than a typical 2-needle carb. The low-speed needle adjusts the fuel flow at idle speed, and the air bleed screw is just the opposite and adjusts the amount of air at idle. Both methods can richen or lean the mixture at idle speed.

In any event, one does not really need to bother with the idle speed adjustment on a FS used for CL stunt or sport, but it might be used for 3-line scale with throttle control. 

Most modelers here simply wire the carb throttle fully open for CL. Some do try to use a venturi. Four-strokes are all about fuel draw or lack thereof. Larger FS's can use a fuel pump system, but the smaller size engines don't have pumps and seem fine on suction alone. And muffler pressure can be used to enhance fuel draw if needed. Others may have specific experience on the Saito 30 in a CL application.

My only experience so far is an OS 26 Surpass FS on a 40" wing Brodak Yak-9 OTS warbird model. I just use the stock carb wide open, but I use a specific setup so I can start the engine at 1/3 throttle, let the engine warm up a bit, then readjust to full speed just before launch. I find that the OS 26 starts a bit easier at 1/3 throttle. Plus, IMO allowing for a brief warm-up is not a bad idea for a FS with all the moving parts. I simply removed the carb throttle lever and inserted a small gear. The gear teeth come into contact with the Surpass choke rod to hold the throttle at a specific setting. This is specific to the OS 26 and 40 Surpass engines that have the choke rod feature.

I'm not sure a Saito 30 FS will be powerful enough for a Nobler ARF. Maybe if you boost the nitro to 20%. I'm running the new Enya SS 35 EX on a Nobler ARF and APC 10-5 sport prop. Great combination as the engine is very light.

In any event I really like the OS 26 FS and how it runs in a CL application. So much so that I am planning to use a larger 40 size FS on a future model, either a Saito FA-40a or OS 40 Surpass. I'm leaning towards the Saito FA-40a as it is a full 2 oz lighter than the 40 Surpass.  On my Yak-9 the OS 26 runs absolutely constant rpm in the air no matter what maneuver I am doing. Plus, the added benefit of 1/2 the fuel use compared to a similar size 2-stroke. And that can be important with nitro fuels being a minimum of $40 US per gallon.

I got my Saito 40 used from a fellow in this forum, can´t remember the name now, with RC carb with the Bon Reeves nylon bolt adaptation. Plenty of power, but something was making the rpm(power) vary a bit. Not sure if it was my tank or the carb mod that was leaking air with vibration, or perhaps something more serious about the engine with valve not properly seated.

    That was an issue back in the 4-stroke era, and it was always eventually traced to small air leaks or small changes in the "throttle" setting. The stock carbs were pretty hopeless, and the solution (as discovered by Ted Fancher in the mid-80s) was to sleeve the carb barrel with a short length of tubing to remove any throttling effect and obviate any leaks around the barrel. The Berringer-style carb (which Bob Reeves brilliantly figured out how to implement with minimal machining) is much less prone to the issue, the venturi system from Steve Moon is entirely immune to it.

   In the few cases people had this issue with the Berringer-style carbs, it got fixed by sealing it somehow (silicone sealant or in one case, inadvisably, heavy silicone vacuum grease).

        Brett