I plan to purchase a new Four Star sixty and a new four stroke engine for it. The question is between the Magum XL , OS, Super Tiger, Thunder Tiger, or any other. I have no experience with small four cycle engines even though I am currently flying two planes with O.S. engines.

Are there any REAL troubles besides individual choice that plauge any of these engines?

I am planning to purchase a .91 FS engine and would cirtainly appreciate any and all comments concerning this purchase.


Please excuse the spelling --- but I am from TEXAS.

Lee K5MRC

Lee-

I'm sure you will get a lot of replies, but here's my stab at it. Super Tigre doesn't make a 4 stroke, as far as I know. Magnum and TT are both OS clones. I have heard good things about Magnum, but not so much about TT. I have a Magnum .80 that I bought used and have just installed. Seems to run fine, but time will tell. I have a Saito .91 which I absolutely love. Runs great and strong with no problems. It would be comparable in price to an OS .91 and about $30 more than a Magnum. Next time I buy a 4 stroke, it will be another Saito.

Saito is also lighter than comparable Magnum, TT and OS models.

-Scott

I have a OS 91 on my Four Star and it flies it superbly. A friend flies his with a TT .91 while still another I know has a Saito 100 and they both fly as well as mine. I also own a Magnum .91 that I like allot. I just don't think you could go wrong with any of these. If you want to try something a bit overpowered and off the wall try the new Saito 125- same size and weight as a Saito 100

The TT is not a clone of the OS. The OS has (I think) a wedge head with two parallel valves. The TT .91 has a himi or penthouse head with two valves slanted toward each other. Also the TT has much longer rocker arms which give more valve lift. It is also a lot more powerfull than the OS or Magnum versions. The designer of the OS Surpass quit and worked on the design of the TT four strokes, so they are what OS would have had if he had stayed.

TT 2-strokes are the posterity of Magnum copies of OS 2-strokes in the 90's.

TT 4-strokes, however, are original design. I've heard of a few problems with the TT .91 4-stroke, particularly with the carb design. My friend can't get his to run right.

I would recommend the Magnum 91, because of the cost. It's plenty strong for a 4*60. If it were an aerobatic or 3D plane, I'd go with Saito or YS.

My error. Sorry. Doesn't change my advice.

-Scott

The only thing wrong with the TT .91 carb is that it is too large. If you install the choke housing, that will take care of that problem.

Lee,

A friend of mine lives in Texas and he assures me that spell check actually works there.

Francis

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I would spend the extra money and buy the Saito .91 or 1.00. In fact, I just did, I bought the 1.00.

Why? Because the Saito 1.00 is much lighter than the OS/Magnum/Thunder Tiger .91 sized engines. The price for replacement parts is lower than OS. Magnum parts are reasonably priced. Thunder Tiger? Who knows? Can you even get them?

The Saito .91 or 1.00 won't require nearly as much fuss/ballast weight in order to get it to balance satisfactorily in the model you specified.

Now, were I trying to balance a biplane or any model that traditionally carried nose weight, I would buy the Magnum .91. Parts are readily available. Technicial support is great and they run very well, once broken-in. If I didn't want to bother with a special break-in treatment, but wanted the other characteristics of the Magnum .91 and expense was no object, I would buy the OS .91 four-stroke.

Thanks to all. If any one else would care to comment I would appreciate all of them. Once again thanks and I will try "spell check" . The trouble is my PHD wife is not allways around to correct my work. I am an engineer and that excuse will just have to get me by, HI HI.

Well, except for "certainly" being spelled cirtainly, I didn't see any problem at all with your spelling. I think your wife should be proud!
Anyway, if you are going to buy the saito, then get the 100. The price difference isn't but about 10 bucks, and you get much more bang for the buck! Great engines, and will turn a 14 X 8 prop like there is no tomorrow. Also, a 15 X 6, and possibly a 16 X 4 (although I've never tried the 16 X 4).

However, the magnum is definitely a great little engine as well. I currently have three saitos, and two magnums. I think my future purchases will definitely be magnums!

I will say, though, that I recently needed to replace some parts on one of my magnum .91's, (due to an inverted "landing"), and had a hard time getting them as they were on constant backorder. It took about 2 months for the valve covers to arrive at hobbypeople. Even Global didn't have them. Anyway, once they got them in, I ordered on and received it within two days--for five bucks. The head also needed a little work (where the rocker cover mounts to it), but the head is still backordered, so my dad just used some JB weld to fix the head back up, and all is well now.--it wasn't any internal working part that was broke on the head, just the post where the valve cover bolt screws into. He (as I said before) rebuilt it with some JB weld, and in the process saved me 61 bucks!

Other than that, no bad experiences at all with magnum. And I presume that parts are hard to come by now because of the popularity of these little engines now a-days. They are probably using every part they can produce just to produce the engines they are selling!

My 4 star 60 flys very well with an os91fs. I also have a couple saito engines. Both brands are very good and easy to get parts for when needed. I use an apc 14x6 prop.

Lee, your posts look pretty good to me!

I have worked with all of the currently availabe naturally aspirated .91 FS engines. I have flown the 4*60 with a Saito .91 and it flew really well but was not a fast model. It has a huge wing area for its weight such that a couple of ounces variation in engine weight and consequent CoG balancing is materially insignificant as far as the airframe's performance is concerned.

The most powerful engine of all the .91 naturally aspirated engines running heavier props (13x9, 13x10 and 14x8 for example) is the OS .91 Surpass. It handily outpulls a Saito .91, TT .91 and Magnum .91 running an APC 13x10 by at least 300 rpm (9200 versus 8800 to 8900). I have compared these engines on the same fuel, same day and same prop and this result has been consistent.

When you lighten the load some, the TT .91 becomes quite competitive. It will swing a 13x8 around 10.000 rpm, pretty much equalling the OS .91 and outperforming the Saito .91. The TT .91 I see most often (a club mate's) is an absolute honey of an engine with good power and an amazingly reliable idle. I can't vouch for consistency with the TT, as I have not seen many examples. The OS .91, Saito .91 and Saito 100 examples I've worked with, as you'd expect with Japanese engineering, have all been very consistent.

The Saito 100 pulls heavy lumber (14x8, 15x6) a little better than the .91s but becomes a little breathless at and above the high nines in my experience. The Saito 100 is quite expensive ($280 odd), which makes one wonder if an additional $50 odd is worth the stretch to buy a YS 1.10, which is much more powerful than any of the aforementioned engines.

I just returned from the local hobby shop, ---She has the four star 60 and all of the above engines ,sato and os, the price is virtully the same. Can
anyone give me a reason to buy either one?

I all ready have two O.S. engines if that makes any difference. I do know that she stocks all OS parts. I am not sure abt. Sato.

I really apprecaite all of the input I have recieved.
Thanks all, Lee K5MRC

In can purchase th Sato 100 for abt the same price , more or less abt. $1.00 dollar US. Both can also be had abt two (2) blocks from my house. Dad Gum I wish everyone had a June at A-1 hobby that close to them.

The cost is abt. the same and the hobby shop stocks all of both manufacuteres parts ; so what to do??


I am leaning toward the OS. because of the experence but the Sato because of the comments here.

Please excuse the spelling but I am from TEXAS

Lee K5MRC

Lee,

Nobody here can make up your mind for you....YOU have to do that. Saito..OS...eeney meeney miney mo....

Either one...you're doing fine. Consider though that you've had good results with your other OS motors, they're stocked right near your house AND the dealer keeps a supply of parts on hand.

Gee whiz.....it's not really such a hard decision is it?

Buy what you know...be happy.

Have fun!

'Race

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Maybe it is time for a new experience, since you already have the OS engines, buy the Saito.

I have a couple of OS 4s, a 91 with a pump and a 120, they both run great, but the only problem with OS in general is; that if you plan to keep them for a long time, they change model so often. When they run out of their spare parts you are out of luck. I have 6 OS 2s and can only get parts for recent models.

both the OS ans Satio are excellant engines, you won't be disappointed with either, Maybe get the lighter engine? or the one that looks nicer!!

Parts availability is rarely an issue with OS. You can generally access a treasure trove of parts via the Tower Hobbies website. It's not quite as straightforward a search as one might like, but the parts are in fact there in many, if not most cases for OS motors going back 15 or more years. As an example, my OS.70 Surpass 1 motor (originally purchased in the late 80's) still has all parts available through Hobby Services.

AFAIC...OS has no rivals in the area of long term product support.

'Race

I did not check with June (at A1 hobbyin Mesquite, Tx) about Satio parts but she normally supplies parts (in sotck) for every thing she sells. I know that I am very lucky to have that type of person within two blocks of home! As an aside I noticed that her prices were the same as the catalogs , if that matters when you need parts!

At the present I am looking at the OS 91 or the Satio 100 if any one would care to comment futher I would appreciate it a lot.

Thanks for all the help,

Lee K5MRC

Lee, I own both of those engines.

You really can't go wrong with either. Both are manufactured in Japan and are therefore built to outstanding levels of quality. They both start and run well from new and don't require a lot of break-in to be flyable.

The Saito is a little lighter, will pull a heavier prop a little better but will use noticeably more fuel when compared to an OS .91 Surpass. With lighter props (where they are spinning at about 10k rpm) there's not a lot of difference in power. They are both extremely reliable but if I had to bet my life on an engine to complete 100 flights without a single deadstick, I'd lean toward to OS.

I'd recommend buying whichever you think looks the coolest.

It sounds like you have a fantastic LHS.

Good luck and don't forget to file a maiden flight report!

I bought a TT91 and messed with it for about one and a half years. I sent it back to TT , used the choke plate, tried all different fuel with no success. The way I finally fixed it was to buy an OS and throw the TT in the garbage. It's complete junk. I have a Magnum .61 that is perfect. That is my advice.

Thanks for all the comments guys.

Too bad, you could have let us help you troubleshoot the engine. Shame you threw it away, that is one really powerfull engine.