rbp

I am looking at a couple engine choices for a gp skybolt and was wondering what would be the best choice. A saito 120, or a os 120 surpass? Is it worth the extra 60.00 for a pumped version or not? Thanks Rick

w8ye

My Feedback: (16)

Unless you want to mount the tank on the CG the pump is a waste of time.

Enjoy,

Jim

FlyingPilgrim

My Feedback: (26)

The pump will add weight (and complexity) to the engine. It will provide constant performance regardless of tank position or model attitude, though. If you need to replace pump parts after a few years of use, you may pay a few bucks for replacement diaphram. I think you will be better off with less weight on this model. I would personally use the Saito 1.20, but that's just my personal preference. Either engine is a fine choice for the Skybolt.

Pepe J

My Feedback: (2)

One of our members has a GP Skybolt with a non-pumped OS 120 in it. Runs and flies well. He had one complaint that the airplane wasn't responsive enough due to the aileron's being limited to the one wing. No biggy.... it's just his preference.
I can't comment if he added additional weight and where for balance with the OS 120? If you're planning on the purchase of a new engine, consider the new Saito 125 or a YS 110 depending on the weight needed up front. A Saito 120 is a hair heavier than 150 which is a hair heavier than the 180. If you need about 33 oz. on the beek of that bird, I would lean toward a 180 or even a YS 140. The way I fig'r it, "GO BIG or GO HOME."

RaceCity

IMO...OS pumped designs have not enjoyed great success in the marketplace. In other words, they cost more, and don't seem to work as well as they should.

I've owned the OS 1.20 FS and would say it's a good motor, albeit heavy. I'd go with the straight, non-pumped motor and be happy.

My $0.02

'Race

PS: As a side note, the 1.20 is the only motor I've ever had that exploded a prop. During the intial break in of mine a long while back, I got to the "peaking out" phase and a Zinger 15-6-10 prop just disintegrated. Scared the crap out of me, and left a big gash in my Dad's aluminum siding from a distance of 20+ feet. While I was scraping out my shorts, my Dad was doing a war dance over his precious siding. Great fun! Glad you weren't there to share the excitement with me.

Keep that in mind the next time you're standing next to a big log turning the big rpms!

IronCross

How about the new Saito 1.25... More power and then either of those...

RaceCity

10oz lighter. That's a LOT. You gotta wonder where they saved the weight. Whisker thin construction is my guess...

No doubt, Saitos tend to be light, but they do so at the expense of structural integrity. Particularly with the "bored" designs.

I've seen more than one shed the jug in a less-than-perfect landing and brother...that's expensive!


Then too...the 1.25 was nowhere to be found 15 years ago when the OS 1.20 was the crown prince of 1.20's.

????

'Race

IronCross

Saito has been "boring" then out for a long time.. Most of there engines are a bored out somthing else it seems like.. I have several of them and have never had nor seen any real weakness in there design from this... Can't wait to get my hands on the 1.25

RaceCity

I'm sure it's a killer. I'd just be curious what they hogged out to save 30% of the weight.


'Race

flyinrain

My Feedback: (25)

I have the OS 120 with pump and it runs great. Rock steady idle at 2000 rpm and excellent throttle transition. Never had a problem with it.

mar345

Unless you are planning to fly serious competition aerobatics forget the pump. They cost more and can be troublesome and more difficult to set up. I had problems with my pumped OS 120 II and converted it to non pumped this past summer. It now runs and idles well, even inverted.
For sport and scale flying either the OS 120E or Saito 120 would would be fine.

reddogarchery

can you pump a saito if so where can i get pump. what performance differance will it make i have the 125

NM2K

My Feedback: (14)

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The only performance difference you will see fitting any type of pump/regulator to the Saito 1.25a is simply being able to run it leaner than you normally would without a pump. We set our engines richer to compensate for those times when the nose is high and the engine is substantially above the fuel tank. Other than that, just a pump/regulator will not cause an increase in horsepower.

A supercharger is a different story altogether.

Look up the Cline and Iron Bay regulators on this site, or do a search engine search. On four-strokes, exhaust pressure obtained from the muffler in conjunction with a one way valve (check valve) in the pressure feed line is used to pressurized the fuel tank, forcing fuel to the engine. The regulator then prevents the engine from being flooded by the now pressurized fuel tank. There are also Perry/Varsane/Conley vacuum pulse and vibrator pulse driven fuel pumps that will assist in delivering fuel to your engine. The latter are not to be used in conjunction with the former.

Frankly, if your model is of normal layout dimensions, you really don't need a fuel pump or regulator. Good old suction works just fine.

ir

I had a OS 120 Surpass-E(without pump) and converted it to pumped with a saito unit.

You would need this

http://www.horizonhobby.com/Products...dID=SAI130T68A

and

http://www.horizonhobby.com/Products...=SAI300TTDP102

Remember this pump unit has another needle to adjust pressure. Its not plug and forget unit, works very well when tuned right.

Also check out

http://saito-engines.info/pumps.html

towards the end of the page

Cheers.

P-40 DRIVER

If Saito can turn a 120 into a 180 without any problems ,they surely should be able to turn a 100 into a 125. OS is a good motor but the specs on that Saito 125 make it a class leader. OS pumper motors have had thier problems over the years. My opinion still stands: The more junk you put in your plane, the more likely someting will fail or cause problems. The non pumped OS or Saito 120 are both dead reliable proven motors, can't see how you would go wrong with either. As with all new product, the jury is still out on the 125. Just a thought, the Chevy small block started out as a 260 cu. inch motor and nobody is going to argue that the 350 was not reliable.

Jimnie

Low,
You are going to find the FA-125a to be very cool.

It does follow the age old Hot Rod method of "no replacement for displacemet". (By the way, small block Chevy was actuall bored and stroked to 400 for some aplications) Bore and stroke increase in the Saito gives the 25% increase in displacement. The cylinder is all new and not just a bored 100 cylinder. It actually looks much nicer. The case has also been redone to accept the longer stroke. The stroke is actually longer than the old (totally different) FA-120. Actually there are not many interchangeable parts between the FA-100 and FA-125 either.

It makes the power to weight ratio a striking difference when you go fly it!

But of course the killer part is the continued hemi head, canted valve setup that allows larger valves than any of the other side by side valve engines and better flow that results. This thing rocks for sure. Trouble is you can't get it! They are out of stock. I am told a shipment will arrive soon but will only give limited stock for sale. The price of success!

Jimnie

Kweasel

My Feedback: (29)

Saito save weight by not using steel cylinder liners and often use a smaller diameter crankshaft. Most engine mfgs are now in a race to the bottom in terms of wieght and price, Saito is leading the charge. As a consumer the Saito is my top choice. If I just wanted the highest manufacturing quality and didn't mind the price or weight then Enya is my top choice.

RaceCity

I'd settle for a bushed con-rod.

J.Paul Saure

I bought a OS120SurpassIII w/pump some time ago for a (still in the box) Greatplanes Extra300s. I didn't run the OS, now I'm selling it because I ordered the Saito125a!!! I was going to put the servos in the tail for balance.... ....it's a 11oz difference!!!

Now, some planes need the nose weight for correct balance. I've seen the original kit Skybolt and it's heavy, maybe the 125 will be too light for balance... The new ARF version is a lot lighter, I think the 125 would be just right!!!

(my oh my, where is the world heading to??[X(] "the ARF is LIGHTER" )

Good luck!

NM2K

My Feedback: (14)

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They saved the weight by not planning on turning it into a 1.80 in the future. <G>

It is based upon the .91 crankcase, which was based upon the .65 crankcase.