rbp

I was wondering how you tell the difference between the older saito 120 and the newer version. Is the older model a good engine or does it need some mods. I'm looking for a engine for a gp skybolt. Any replies are appreciated Thanks Rick

w8ye

My Feedback: (16)

The 120S is the newer one.

A used one may have had parts mixed and matched.

It gets pretty deep inti the differences.

Enjoy,

Jim

carlbecker

My Feedback: (3)

Older ones are heavier, may have higher compression and run on lower nitro. I used an older Saito 120 in my GP stearman for balance. What a sweet running engine.

Carl

FlyingPilgrim

My Feedback: (26)

Look at the factory pictures of the current production model. The older 120 is quite a bit bulkier, and is heavier. There have been minor mods to the current production model with the same basic size and design (and some cam design changes). The older one is really obvious when you see the two side by side. The newer one has had different intake manifold designs including the older curved intake tube, where the newer one has the 90 degree manifold that screws into the block with a nut. There were versions with choke plates, too. Bill will certainly post some pics of both models before the day is through...

Will Robinson...

William Robison

My Feedback: (3)

OK. The only "Real" differences in the early and late FA-120 engines is the ABC cylinder and "Normal" cam on the early models. The later ones have AAC cylinders and the high lift cam.

Easy ID for the ABC/AAC cylinders is the cooling fins. Look at the cam box. If the fins reach out over the box, it's ABC. The AAC cylinder has smaller fins, the cam can be removed with the cylinder in place.

The low and high cams can be differentiated by the tappet guides extending above the top of the cam box with the high cam.

There are other internal differences, for example the early FA-120 engines had a smaller rear bearing than the later ones, and the valve keepers have been changed to split collets on the later engines in place of the "C" clips on the earlier valves.

There have even been three different carbs on them. The earliest had an air bleed type, and there have been two versions of the TN carb. A kit is available to bring the early TN up to late specification, but if your engine is running fine don't bother with it. And if you have one with an air bleed carb treasure it - it's nothing like any other air bleed you've seen. Saito didn't drop it because the TN was better, but because the TN was less expensive to make.

Pictures:
1) FA-120 ABC, low cam. Note fins
2) FA-120S AAC, high cam. Note fins
3) FA-120 ABC cylinder on left, FA-120S AAC cylinder on right, note size of fins.
4) Low cam box on left, high cam box on right. Note tappet guides on high cam box.

Bill.

William Robison

My Feedback: (3)

A further point that might be of interest - the FA-120 is now discontinued in all versions, replaced by the FA-125a.

Bill.

William Robison

My Feedback: (3)

rbp:

Sorry, I didn't answer your basic question.

The older ABC/low cam FA-120 is my favorite Saito single cylinder engine. It is heavier than the later engines, and less powerful with the mild cam. But these two things also make it a very easy engine to operate, and contribute to its being just about the smoothest running of all.

Bill.

flyathome

My Feedback: (7)

I have an older Saito FA-120S that has gold rocker covers. I bought it used quite a few years ago. I am still flying it today in a Diabolic. It runs like a fine watch. I was wondering if anyone has any idea how old it is.

Thanks,

Steve

donkey doctor

Hello; My Saito 120 has gold rocker covers too. I bought that one new in 95 in Millet Alberta. I was offered an older heavier one for $10 less up in Edmonton, but I went for the lighter one and haven't been dissappointed at all, it's a great engine. So it would be late 94 early 95 was when these engines hit the stores.

Rendegade

Sorry to drag up an old thread, but I've been doing research on the air bleed carbs on the old big fins and there's comflicting information on tuning them.

Whats the right way?

rcdude7

My Feedback: (264)

Not sure I follow what you are asking but, I have my old 120 in my hand now, there is a air bleed to trim the idle mixture and a hi-speed needle, no other adjustments on this carb, my old 2.70 twin is the same.

Rendegade

It also has a rotating disc that the HS needle mounts into. The disc is machined with a reducing slot, like a comma, to adjust the mixture as the carb barrel rotates.

I've read of people closing the idle air bleed completely and adjusting the mix with the rotating barrel to acheive a good transition.

Not sure that is correct though.

My thoughts would be that you get your HS needle sorted, look for a decent transition by rotating the disc and adjust your idle with the air bleed.

Any thoughts?

earlwb

The Saito 3 mixture carb (big head 1.20) is NOT an airbleed type carb. It is an automixture carb with an airbleed idle trim. I find it best to adjust it as follows:
Close the airbleed completely.
Set the high speed mixture with the needle valve to be rich 200 off peak rpm.  
Adjust the idle mixture and speed ( throttle position) to get the rpm you want at the leanest mixture strength that allows steady running with the brass looking disk on the side of the carb.
Now test for transition from idle to high speed. If it is good you are finished.

Now if the transition indicates that the mid range is lean the adjustment for this is a little counter intuitive.
To richen the mid range open up the idle trim airbleed and readjust the disk mixture adjustment (richen) to get back the desired idle mixture strength.  To recap lean the idle with the airbleed richen it back to what you want with the disk. This results in a mid range that is richer than when you started but with the idle mixture strength set at its proper lean mixture.
Of course there is a little give and take with the mixtures but the compromises are a lot less with the Saito 3 mixture adjustment carb than any true airbleed carb.

That old three mixture carb is still much better than most ,any of the, '2 needle" carbs. I regret selling my old 1.20 years ago, but someone really wanted it bad, and I didn't have a plane at the moment for it.

Rendegade

Sorted, and runs like a sewing machine, if a little smokey on a snapped open throttle. TBH I could lean it out a touch more, as the throttle servo speed isnt anywhere near an "arm" speed, but she revs like a little beauty.

Cheers!