Saito FA-82 vs. OS FS-a 81 - RC Groups
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Dec 31, 2008, 12:57 PM
waay's Avatar

Saito FA-82 vs. OS FS-a 81

Those of you out there that are looking for a performance 4 stroke for a .60 size airplane OS Engines has come out with the OS FS-a 81. Recently I have picked up an Extreme Flight Extra 300. Suggested in the manual is the Saito FA-82a, but the manual was written before the release of the OS. Since I have had good luck with OS in the past (and have never owned a Saito), I decided to try out the new OS even though the price was significantly higher for the same class engine.

When the engine arrived I noticed that the packaging was different from my previous OS engines. In stead of the usual bag and spray foam packaging the OS FS-a 81 came in the standard blue OS box but the engine was enclosed in a plastic bag within an air pocket plastic enclosure. Now the plastic holding the air was a thick plastic to prevent puncture with multiple individual sealed air compartments. This system did not isolate movement of the engine within the box, but the engine did arrive undamaged and well oiled. There was a thick soft plastic tube around the drive shaft to keep the prop washer from bouncing around on the shaft and causing damage. This also served to hold the drive washer in place during shipping. This is really important since the drive washer does slide off and it would be easy to lose the keeper key.

Upon initial inspection of the engine I did notice some nice features. A velocity stack comes standard and installed. The mounting surfaces are machined which made mounting on an OS aluminum radial mount a perfect machined fit. The muffler presents a low profile and easily fits inside the cowl. The rotating exit port of the muffler makes positioning the muffler a breeze.

One thing I did not like about the initial setup is the throttle arm requires very little movement to extend throughout the entire range of the throttle. This required me to cut down the servo throw significantly. In doing so it also shortened my throttle cut button on my transmitter. I had to fool with the radio for a bit to get enough throw in the throttle cut to actually cut off the air supply. I had to move the EZ-connector all the way to the inside hole on the servo arm to prevent the servo from growling itself into oblivion.

At the field I filled up with my old stand by PowerMaster 20/20 synthetic. Three bumps on the starter and the FS-a 81 roared to life for the first time. Following the fat/lean procedure in the OS manual I proceeded with the break-in process. I did notice drops of oil coming from what appeared to be my spinner. Since the exhaust is coming out the bottom of the plane I found this a bit odd, but continued to break in. The first thing I notice about the engine is that it is quiet. The APC 14x4W is making more noise than the engine. The first flight I had the idle set at 3300 and max set at 8800; nice and fat. The Extreme flight took off without incident. 2 clicks of elevator and one click on ailerons and it would track like it was on rails. The CG is a bit forward for my liking but about where I usually run on a maiden. The timer on the receiver is set for 10 minutes. I landed 25 seconds short of the timer and killed the engine so I would not roll past the flight line with a running engine (big no-no at the field), but because the idle was so high the plane would not stop.

The first thing I notice is that my entire cowl is completely covered in oil. The inside of the cowl has even more oil in it (which is now dripping onto the taxiway) I roll the plane off the taxiway onto the grass. Head temp is right around 114 degrees, nice and cool. I remove the cowl and the entire engine box and cowl are coated in oil. Now I am glad I fuel proofed the entire area with epoxy. There is still about half of a tank left of the 12oz tank in the plane. Pretty good considering how fat I am running but then again there were only a few full throttle passes. I start the engine without the cowl and find that the oil is coming from the front main bearing.

The 10 following flights (getting increasingly leaner) go without incident but require a good wipe down of the entire front half of the plane. One good thing is that the oil coming out is a nice clean translucent pink. One thing I do notice is that during flight there is a drop in RPM and a cloud of dark smoke that draw lines in the sky. The RPM drop is less than a second and the line of dark smoke is about 6 to 8 feet long depending on how fast I am going. It happens at rather consistent intervals. The higher the throttle is the more noticeable the RPM drop. I believe that when the new oil delivery system is burning off oil is what is causing the dark smoke and RPM drop.

Now that I have a few tanks through the engine I tune it 3 clicks fat from max RPM. This puts the 14x4W at 9300 RPM. I lean out the bottom end so she raps up nice and quick without bogging out. I got the idle down to 2800 RPM. Below that the reliability went down, which is fine for a new engine and I have a tendency to tune conservatively with newer engines until I get two gallons through it.

Now that it is tuned up it is leaking less oil but the top of my cowl is comes in with a layer of pink oil covering eighty percent of the cowl top. After a few flights I decide that the front main seal must be bad. I am quite disappointed that I have to send a bran new engine back.

I call Hobby Services to see if I can get a replacement engine while they fix mine. The answer was a flat “no” with diplomacy. Even if I gave them my credit card (which is normal procedure for a cross ship exchange) the answer was still no. So now I am going to be without my bran new engine for 3 weeks. Needless to say this makes me unhappy so there is only one thing to do, buy my own replacement so I can fly while this one is in the shop. So I went online and ordered a Saito FA-82a from Rogue RC (stand up guys). Had Hobby Services agreed to replace the bran new OS with no downtime I would have never owned the Saito. Sometimes it pays to go the extra mile…

When the Saito arrived and I opened the box and was greeted with dense foam cut to form a movement isolating shape right around the engine and good protection around the needle valve. There was a separate cutout for the muffler and manifold. Along with the muffler was a bag with a valve tuning kit that includes 2 hex wrenches, a box wench and a feeler gage. The bag that was around the engine was a thin plastic that looked rather flimsy; like if it got a hole anywhere in it any stress in the area would cause the entire bag to split in two. The Saito (unlike the OS) was for the most part dry of any outside oil. No oil residue inside the bag. The only thing that had a thin coat of oil on the outside was the exhaust manifold. This kind of makes sense since everything is either stainless or aluminum accept for the exhaust manifold.

So upon checking the engine I noticed that the throttle lever was on the wrong side. I checked the manual to see if it was reversible. I found nothing regarding the subject in the manual. I logged on to the internet and found on Saito’s website a FAQ that asked if the carburetor was reversible; the answer: yes. Talk about short and sweet. I guess they figure any idiot that can’t remove 2 screws without breaking something was doomed anyway so why bother? So I rotated the carburetor so I won’t have to displace my current throttle servo and change my pushrod.

Well on to getting the engine on the plane. The OS has a wider footprint than the Saito so I had to use a composite mount. This required moving bind nuts which I was trying to avoid but there was nothing I could do to get the OS mount to work aside from cutting it in half and taking a quarter inch out of the middle. Amazingly enough I drilled the holes in the mount all even so they lined right up (I gotta get one of those top flight center punches). Only after I had the engine on the firewall did I measure the distance from firewall to drive nut, oops sticking out about ¼ inch too much. For break-in I am going to leave it there (hell who am I kidding its never going to move unless the mount breaks). If there is too much right thrust when I fly I will get a new mount. The throttle arm required a significantly longer throw to completely open or close the throttle body. As it ends up I had to turn the throttle servo’s arm 180 degrees and move the EZ connect back out to the outside hole. Thankfully that was all that was needed in the linkage department. On the radio I went from 17% to 97% for throws in both directions. It’s probably psychological but it feels better to me.

It is time to hit the field and try out this new power plant. I decided to leave cowl at home until I can make the necessary modifications to fit the new exhaust. Once I got to the field it was a great day to fly but I had to content myself with watching since I wanted to get the engine broken-in properly. I filled the plane up with my trusty 20/20 hooked up the glow igniter bumped the starter once, twice, pop! Whirr. (insert expletives here). The third bump caused a backfire subsequently resulting in me having to remove the spinner and retighten the prop nut and bind nut. Ok all back together, add glow, bump the starter pop! Whirr… (insert more expletives and some kicking of dirt). Sigh. Well off with the spinner, retighten, and back on with it. Well third time is a charm right? Bump the starter and the engine roared to life. Check tachometer and lock the engine in at 3800 RPM. The second I turned the glow off the engine died. Running as fat as it is and at a low RPM it makes sense, however at the time I was a bit worried about my field battery so I turned the igniter off. Hindsight is 20/20. So after removing the spinner 3 more times because of kickbacks and getting the engine running at below 4000 RPM I left the glow on. Usually I don’t operate my glow igniters for more than 30 seconds. If the engine is not running by then something is wrong. Leaving a glow igniter on for 15 minutes threw my field battery for a loop and it subsequently keeled over and flipped me off. It sill had enough juice to run either the glow igniter or the starter, not both. So I dig around in my field box and find my old glow igniter. This works and kept me going for the rest of the break-in process.

After some of the full throttle break-in bursts I came to realize that this Saito could pull a freight train. What a difference. Where the OS is a smooth & quiet running well oiled (pun intended) machine the Saito is a brute force animal in a cage waiting to be let out, and when you do let it out watch out! With the bottom end still fat the engine is still “hammering” so it shakes my plane so badly that one of my servo arms fell off. Luckily I found the bolt and put it back on then checked the rest to make sure they were tight. Trying to keep the exhaust tight is an exercise in futility. The power curves of the two engines are night and day. The OS has a much slower spool up but seems to like top end a bit better than the Saito. The Saito was doing its best to test the strength of the engine mount. I could watch the mount flex alarmingly when I would throttle up quickly. The power curve seems to roll off at about 85% throttle.

So now it’s time for a flight. I fill the tank back up. The last 2 tanks the engine has been starting right up with just a bump from the starter. It has been idling reliably at about 2700 rpm but has a tendency to load up since the bottom end is still fat. Tuned fat for break-in it has been turning 9600 RPM. I hook up the glow and bump the starter…nothing. Bump it again, nada. Bump it a 3rd time and I know I am not getting glow. Well I am not one to tempt fate. Lets see, lost servo arm to half my elevator, one of my wheel pants came off, and not the glow igniter dies… someone is trying to tell me something. I learned long ago that if more than 2 things go wrong before you get into the air then pack up and go home. Come back once things are fixed properly. Holding to that protocol, I empty the fuel tank and clean up and head home.

The next weekend was the maiden flight with the Saito. The idle is quite high to keep the engine running since the bottom end is still set at the factory setting. I spent the rest of the day just putting around. I really don’t bother with my sub trims till the engine is running the way I want it, but I did get the plane to fly relatively straight. It lands pretty hot and won’t stop (unless I hit the grass) because the idle is too high, but I would rather have a reliable idle. The only excitement was a throttle servo failure. The servo died at just over idle, enough to keep the plane in the air but unable to climb. The landing was less than ideal. No damage to the airframe or engine, but a wheel pant got broken when the plane went nose over in the grass at an alarming speed. The wheel pants came off and I replaced the servo and added an oil splash guard (half of a spinner package cut out and epoxy it over the servo then cut out a hole for the linkage). I continued the flights and began to check the CG (little nose heavy) and adjusted the sub trims to get my tracking dialed.
After 45-50 minutes of run time it is time to tune the bottom end. Sparing the details I get the bottom end leaned out and what a difference! Spool up is almost instant now. The engine runs much smoother now and is no longer abusing my airframe. I only got in about 3 tanks of fuel before the current gallon is gone. Since it is nearing three o’clock I decide to call it a day and head home.
The next morning at about eight o’clock I am out at the field by myself. The bottom end needed fatting up with the new fuel (still 20/20 but a different can). I get in two flights at ten minutes each and I notice that I am landing with ¾ tank of fuel left. I extend my timer to fifteen minutes and get in two more flights. On the third flight it begins to rain lightly so I decide to land to prevent my transmitter from getting wet. I thought the rain would stop after a bit but as it turns out that was the end of my day. The rain continued and for an hour before I packed up and went home.

So the big question is which engine is better?? Well I am going to say that it boils down to what type of flying you do. If you are a scale or sport flyer looking for a versatile engine that will run on just about any fuel, or if you fly at a field with strict noise restrictions I would suggest the OS. If you are an extreme performance or 3D flyer then the Saito is your ticket.

Suggestions for manufacturers:
Saito: Include a velocity stack with the engine and remove the valve tuning kit. The valve tuning kit will maybe be used once in a six month period where as a velocity stack would be used on a daily basis. The respective costs are about the same so I would suggest opting for something the customer would use more often rather than twice a year.
OS: If you want any chance at competing with the Saito you will have to drop the price of this engine to a comparable price bracket as the Saito. Many people will opt to go with an OS when given the choice between two comparable engines of similar displacement and price bracket.

Since my OS came with something wrong keep in mind that it could have a bearing on my experience with the engine performance. Also keep in mind that OS does not manufacturer the bearings so I just got unlucky. Although it could have been handled by Hobby Services a bit better I have a hard time faulting OS for a bad bearing seal. I think that letting the OS breathe better would increase performance some but not enough to match the Saito. The Saito has a 14mm exhaust port and the OS has a 12mm exhaust port.

I used the same APC 14x4W on both engines.
OS Operating RPM: 9300
OS idle RPM: 2240
Saito Operating RPM: 10200
Saito idle RPM: 2270

Side note: Recently I added a Keleo pitts muffler to the Saito. The Keleo 91/100 size pitts muffler fits perfectly on the FA-82.

Special thanks to Rogue RC and Keleo Creations. They both had errors on their websites (prices lower than they should have been) and both honored their advertised price even though it was a mistake. That is the kind of customer service that will keep me going back.
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Dec 31, 2008, 12:59 PM
waay's Avatar
[Feb 04 2009]

Well I got the OS 81 FS-a back from hobby services. They replaced the engine with a new one with the notes “Excessive oil leaking out of main bearing”. Hobby services had the engine for less than 48 hours before they determined the problem. Their website is great for letting their customers know what is going on.

So the biggest problem I have now is deciding which airframe to put it on. I decided to go with the hanger 9 twist for a few reasons. The deciding factor was the amount of time required to get the plane flying and the twist required very little. The migration of two bind nuts to accommodate the OS mount, change out throttle pushrod, and it was ready to go. Another reason I went with the twist is it is not a scale plane so no cowl or anything to get in the way for tuning the engine. I am comfortable with the airframe and would not be too put out should I pack it in. There are more patches on this airframe than anything airworthy has a right to have, but this thing refuses to die which has made it an excellent standby plane for my trips to the field in less than ideal weather. As unsightly as it is it still tears holes in the sky above our field.

Unfortunately for the initial break-in and testing I did not have the prop I wanted to run with. I ended up using the APC 13x4W that was on the OS 55ax that was previously on the airframe. Once I got to the field I had to be careful not to over rev the new engine because I was under-propped so I ran pretty fat. Best to err on the side of caution.

As with all my previous OS engines all it took was a prime and two bumps on the starter it started right up. Two tanks on the ground letting it cool between runs (which did not take long since the wind chill was well below freezing). After getting a reliable idle and throttle up it was time to take it up. One last flight check and I taxied her out. Since the idle was a little high I had to use the tail wheel to slow it down. I had to wait for the wind because it was gusting at about 19 mph which is a little more than I am comfortable with but that’s why I am using an older airframe. Power was good on takeoff and the throttle response is what I expect it to be during break-in.

Fast forward four tanks of fuel with relatively uneventful flights and white knuckle landings and I decide it is time to tune the bottom end. It could use a few more tanks but it loads up pretty quick and I want a more reliable idle. I tune the bottom end retune the top end (still fat). I taxi out and hit the throttle. The plane took off like it was assisted by a steam ram. One thing is for sure, the previous engine had something more than a leaky main bearing wrong with it. The engine is running much smoother now but I am still breaking it in so I don’t go crazy.

As it turns out that was my last flight for the day as I broke my gear off upon landing. This weekend looks like there will be much more favorable flying conditions and I will have my plane with the Saito 82 out there also.

The weekend was great flying weather and I burned about a gallon and a half of Powermaster 20/20 between the Saito and OS. I got the 14x4W on the OS and was able to lean it out without exceeding the maximum suggested RPM. My opinion of the OS FS-a 81 has changed a bit. It is a great engine. It made my twist (40) into a new plane (or rocket)

So the big question is how does the OS FS-a 81 compare to the Saito FA-82? The short answer is: very closely. Operating RPM of the OS was 250 RPM shy of the Saito, both were over 10K with a 14x4W. Throttle response is similar. Though I have no test equipment to give tangible evidence the OS definitely seemed to spool up from idle faster than the Saito but this may be tuning or the fact the airframe it is on is smaller. Midrange performance is nearly identical. Idle is likewise similar but the Saito does take much longer to load up. The OS seems to run smoother and quieter at lower and mid range RPMs. Ease of Break-in was definitely the OS but this is primarily because the manufacturer suggested methods are so different.

In the end I would say that OS has produced a competitive engine to the Saito 82 for just about any type of RC enthusiast. The biggest difference between the two engines that I can see is the price. So for all you hardcore OS guys you have an engine on par with the Saito 82. For everyone else you now have two choices for supercharging your 60 size airframe. My suggestion is buy whichever is best fits your price and availability criteria. You cant go wrong with either.
Last edited by waay; Feb 04, 2009 at 05:46 PM.
Dec 31, 2008, 01:45 PM
The reviewer
XJet's Avatar
Interesting observations.

None of my Saitos have ever backfired but they will run backwards if you have them too wet when starting.

I have no idea why but OS (and Saito) seem to be developing a history of shipping engines with "less than good" bearings.

Once you change them (using third-party bearings) they're fine but the factory-fitted units don't really seem to last as long as the replacements.
Dec 31, 2008, 02:50 PM
Registered User
Nice review. I have several OS engines and at times have looked at the Saito's but haven't ever bought one. IMHO the Saito has the best looks of them all though.
Dec 31, 2008, 05:10 PM
Suspended Account
Pick one. I have many OS and Saito four cycle engines and I would buy either brand as well as Enya and YS. At this time I am using Three OS and two Saitos. NEVER had a bearing problem with any of them. Of course I use straight castor oil and 10% nitro and don't strain my engines.
Dec 31, 2008, 05:30 PM
Registered User
Jimmy Hoffa's Avatar
Thanks for the report.

You are correct in noting the need of a velocity stack on the Saito. The stack does not improve power but does improve fuel economy and keeps the engine compartment much cleaner. IMHO it's a must have item.

Saito Velocity Stack

Jan 01, 2009, 02:33 PM
Registered User Wannabe
rodneygt's Avatar
Nice comparison.

My saito 82 has the velocity stack. It is the golden knight version. I knew the non-gk versions lacked the stack. I dont know if the gk still comes with it or not.
Jan 03, 2009, 03:22 AM
"The OS has a wider footprint than the Saito so I had to use a composite mount."


After spending over $300 plus for a brand new engine, it would make me nervous if I noticed what you noticed. Why? Because it appears as though they have left room in the crankcase for expansion. Can you imagine what the resale value of your engine will be when the latest .91 comes out?

Kind of like owning a YS .53 after the .63 came out.

I'll just hold on to my two Saito .82 engines. Thanks for the report. I do appreciate it.

Ed Cregger
Jan 03, 2009, 12:05 PM
Dieselized User
gkamysz's Avatar
Originally Posted by Artisan
After spending over $300 plus for a brand new engine, it would make me nervous if I noticed what you noticed. Why? Because it appears as though they have left room in the crankcase for expansion. Can you imagine what the resale value of your engine will be when the latest .91 comes out?
It will be what 8-10 years until a new series is released? Who cares what it will be worth then. The first Surpass II engines were released in 1996, 12 years ago! There are many taking advantage of recent price increases by selling off engines that they won't be using and getting back what the paid or more. I don't see new engine prices going down.

Jan 03, 2009, 02:15 PM
Low, slow and dirty
Very good article Waay. At tax time I'll be buying either a saito 100 or OS 91. I know one thing, I'm not into spending 300.00 for a engine that needs to be sent back. I'll probally buy it at the hobby shop that I do business with. If there was a problem I'd demand they give me another. Saito should include that velocity stack with all there engines. When a company starts putting out a shaddy product on a constant basis, It's sites like these that gets the word out.I wonder how many others have had to send their brand new engines back? I own a OS-70, mag-52. OS-56 and a Saito-82. So far so good no problems.
Jan 03, 2009, 02:22 PM
Dieselized User
gkamysz's Avatar
Originally Posted by j. marquis
Very good article Waay. At tax time I'll be buying either a saito 100 or OS 91. I know one thing, I'm not into spending 300.00 for a engine that needs to be sent back. I'll probally buy it at the hobby shop that I do business with. If there was a problem I'd demand they give me another. Saito should include that velocity stack with all there engines. When a company starts putting out a shaddy product on a constant basis, It's sites like these that gets the word out.I wonder how many others have had to send their brand new engines back? I own a OS-70, mag-52. OS-56 and a Saito-82. So far so good no problems.
How does one defective engine make OS engines a poor product?

Jan 04, 2009, 07:34 AM
Low, slow and dirty
Like I said , on a constant basis. One or two in a hundred isn't a constant basis. ten or more in a hundred is starting to be. OS or hobby services should of sent him another one after he sent his defective back. I wonder if there's an internal pressure problem with this new design. We'll found out because many more will be sending their engines back
Jan 05, 2009, 01:09 PM
Registered User
The prices that Hobbico is charging for the new O.S. Max four strokes are pretty breath-taking. They've turned Saito into a value brand.

I'm sure that the new FS56-a, FS72-a, FS81-a, and FS110-a are all spectacular engines. I just can't imagine paying those prices when my local hobby store is still selling Saitos at pre-markup pricing ($249.99 for a Saito .82 versus $339.99 for the FS81-a).

I think both four stroke lines are terrific, but I can't imagine any reason to buy an O.S. Max four stroke when a comparable Saito model is available for $90 less.

It's even more mind-boggelling to think that Hobbico is pricing the FS56-a at a whopping $299.99 while Hobby People is blowing out their Magnum XL .52 RFS for $74.99 with free shipping. You can buy the Magnum .52 RFS and a Saito .56 and still have money left over for a pizza all for what the FS56-a costs.
Jan 05, 2009, 01:46 PM
Registered User
Yeah, I can buy 2 Magnum .91fs for 1 OS .81fs. When the hobbypeople sale was on I could buy 4 Magnum .52fs for 1 OS .56fs......... I like OS but they have priced themselves out of what I'm willing to pay which is ok since I'm just as happpy with my Magnum engines as I ever was with the OS's I have.
Jan 05, 2009, 02:04 PM
Dieselized User
gkamysz's Avatar
New engine prices are high. I rarely buy new. I just picked up an NIB Saito FA-30 for 110. I paid $60 for a good used FA-30 last year at a swap meet. The Magnum 52RFS deal was too good to pass up, so I bought 2. I didn't want to potentially scrap any OS parts for what I'm going to do with them. They aren't OS or Saito but they do work, most of the time.

Buy what you like, it's all for fun anyway.


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