Hello I was wondering what four stroke I could get on a avistar. I thought a saito FA-56 will be equivalent to a 46 two stroke but I’m not sure. I do like the four stroke sound and that is really why I would pick one. Also I hear that they last longer but not positive.

Thanks

A Magnum or O.S 52 four stroke would be good choices. If you have a very fat wallet, the new O.S. 56 four stroke would also be a good choice, other than the outragious price. You can get two Magnum 52's for the price of one of those. If you really want performance, a 70 would work, but it caries the penitaly of extra weight.

Don

My opinon is that an OS46AX is a near perfect engine for your Avistar but if you want a four stroke then you will have to go bigger than the 56 to match a 46 two stroke. Save yourself some headaches and stay with a Saito or OS fourstroke. A Saito 72 or maybe even the new 62 would be a good combo. The OS 70 is a lot heavier and may be discontinued soon and the new 56 OS isn't a proven commodity yet.. so the Saito might be your best option IMHO.
Fred

I don’t know that the saito 72 will work. It is almost double the weight and that is a lot of balancing. But that is without mufflers on both.

seemefly, the Avistar is smaller than most trainers. I have an O.S. .52 on mine and it has plenty of power. The Saito .72 would be overkill but would work fine. It is only a little heavier than most .46 two strokes, not almost double the weight. You should be able to balance the plane with a four stroke by moving the battery back.

like i said that is without the muffler so i dont know. if the 72 is overkill what will work

The Avistar is a small plane and anything bigger than a Magnum 52 and 61, OS 48, 52, and 56, or Saito 50. 56, and 62 would destroy the design parameters of the plane so badly that they wouldn't be an effective conversion.

Great Planes never even intended the plane to have a four stroke engine in the first place.

Seemefly, please save your money. Use the Avistar to learn to fly. It is, as had been said, perfectly suited for a .46 BB engine and perfoms wonderfully with one. Put the money into a Saito 1.00 and put that in a Sig Four Star 60

Seemefly, I have actually flown an Avistar with all the engines I described in a previous post. I flew the same one for two or more years before selling it. I started with a Thunder Tiger 46 then went to an OS46FX, then to a Saito 56 and finally to a Saito 72. Between the FX and Saito 56 I had to rebuild it due to a lower than dirt landing while buddy boxing a newbe. The reason for all the engines was that I used the Avistar to break in those engines for other projects and the Avistar was a fun way to do it. A Saito 56 or OS52 will not over power the plane and the Saito 72 was the most fun but I had to make some changes so it would have sufficient clearance for the bigger prop. The Thunder Tiger and FX were sort of fast. To accommodate the different engines all I had to do was move the battery around as the engines mentioned are all close to the same weight.
Fred

well as you say that the 72 you need changing to fit the prop. what changes did you make?
i will probebly go with a 46ax but wanted to know what 4 strokes i could get. thank you all for the help

Also keep in mind that if you are doing a conversion, then the linkage for the throttle has to be considered.

I put an OS 52 Surpass in a plane that was designed for a two stroke engine. The linkage issue was a real pain in the butt.

Look it over carefully before making any changes or choices and make sure it's what you want.

Personally, I would go with the OS 46 two stroke. I have one on a Hobbico Super Star trainer and it is plenty adequate for that plane.

CGr.

I would save my money and just use a 2 stroke. I have one with a Super Tiger 45 -PLENTY of power. I get unlimited verticle. If you are leaning on the avistar...chances are your next plane will require a bigger 4 stroke than what you are putting in the Avistar. Good Luck.

A Super Tigre G-40 2-stroke would fly the Avistar very, very well and they're $49.99 before discounts. A Thunder Tiger F-54s or F-75s would both weigh less than an O.S. .46 AX, as would a Magnum XL .52 RFS or a Saito .56, .62, or .72.

I really like the way the Avistar flies with a .40 LA on the nose, however, and a .46 LA would be a nice step up if you wanted some extra power for windy days and aerobatic flying.

The Avistar will fly wonderfully with the least expensive engines on the market. If you'd rather spend more to enjoy the sound of a four-stroke, I'd suggest the Magnum XL .52 RFS would be a reasonably price model that would fit the Avistar very well. The weight is less than a ball-bearing .46 2-stroke and the carburator is reversable so you don't have to redo the stock throttle linkage setup.

Considering how closely the Magnum XL .52 RFS is priced to the O.S. .46 AX, I'm surprised that more folks don't choose the .52 RFS for .40-sized trainers.

The Magnum .52 RFS works great on high wing trainers. I have one on a LT40 . Sips fuel and starts easy.
I agree with biged, for $49.99 the GS .40 is a good buy . Had one on the LT 40 ,before I put the 4 stroke on. I still have it and it`s pulling an old Eagle trainer around.

We put a Saito 56 on my son's LT40 and it flys it great. Its a good combo and just sounds right.

As to the throttle operation with a 4 stroke, it's very easy. Take the tank hatch off. Configure the 4 stroke throttle arm to the up position. Use a pushrod (bicycle spoke?) from servo to throttle arm. It'll need a small bend depending on the engine height and servo. Once that's all operating freely (sometimes it needs a nick in the top of the firewall), dremel out the hatch front edge to clear it. Now thin CA all over wherever cuts were made, go fly!

I would seriously hold off on the 4 stroke in a trainer for two reasons:


One you're getting into a lot of money on a motor for a .40 sized engine, when reality is most people want a .60 sized sport plane for #2.....

Two, you're getting into a lot of money on a motor that you're quite likely to break at some point. EVERYONE crashes a trainer, and if it's a good hard nose hit, a cheap two stroke is both more survivable, and cheaply replaced, than the 4 stroke.

Look at the sait 1.00 for a 4* or tiger 60. I maidened mine out yesterday, and it flew beautifully. Pulls off the runway at half throttle, and will fly around at half throttle faster than your trainer will, but puts the brakes on more quickly than my hobbistar ever did(almost stalled it on approach the first time, I wasn't expecting that at all......)

It is my opinion that something in the weight and power range of the OS .46LA is perfect for the Avistar. Get any heavier and you'll be adding lead to the back.

The avistar is on the small side compared with something like a LT40