I just got an Aviomodelli Bipe Special WS 55”, 7,5 lb, the manufacturer suggests a 10cc 2 stroke engine. I have to choose between these 3 engines: TT GP61, Supertigre G75, MVVS 77 ( cost here in Italy is almost the same) … which is best?

thanx
david

A member in my club flies it with an OS FS-91 4-stroke. No problem.

After all the plane is so much tail heavy that you have to open wholes throughout the tail part (stabilizer and fin) in order to avoid too much lead weight on the nose.

So don't worry about engine's weight.

Stelios

thanx stelios

I found that the manufacturer suggests a TT pro 61 which weights 740g, the Os fs 91 is 686, so I think the TT 91 4-stroke, about 730g, should be perfect to avoid a tail heavy plane. The problem is i don't know anything about this engine!

Thunder Tiger .91 4 cycle engines seem to be pretty good. We have a few folks in our clubs and they like them. Nothing beats a 4 cycle in a bipe, but then again some budgets (like mine) don't always allow for that!

I have os 91 4 stroke on mine. I can not balanced. Tail is heavy. I moved engine about 2" forward. That move didnt help. Now planing to put Saito 120 in it. I t will be hard to fit that engine under cowl. And I'm not sure , firewall is strong to hold that engine or
not?
Thx

The Supertiger 75 is a great engine. It weight is not much more than the OS 61, IMO, is now a better engine, providing much more power than the OS. The Thunder Tiger is also an excellent engine for the price, but the Supertiger will give you a "home field advantage" with parts availability.

Try to stay within the manufacturers engine range for that particular bipe. It will work best that way. Over powering with a much larger engine will often bring a weight penalty that the extra horse power will not clearly overcome.

I finally got a TT 91 4 stroke, I heard good things about this engine (more power than the OS, more weight to balance the tail)! I'm also planning to replace the plastic firewall with 1/2" plywood secured with some extra screws, as I did with my other aviomodelli Tango. The firewall included seems to be a little weak ... In the tango the front gear is attached to the firewall which broke after an almost perfect landing!!!!
Plane Racer good looking color scheme! What is the final weight of your bipe? I'm afraid mine will be more than the 3600 gr stated on the box! And which paint did you use?

thank you
David74

David74,
I used listeKote paint with clear coat on it. Total weight is about 9 pounds with saito 120. Finally got balanced. No balance at all with
other engines. I try to moved battery and reciver , and moved engine forward. no balance. Now, I have a 1 pound overweight .
I think that is ok.
thx

Hey!!
This is a nice flying plane! Saito 120 is very good motor for that. Lots of power, nice handling on the ground.
Here is a couple pictures.

Thx.

nice shots PlaneRacer!!! This plane does look really good.. what about dead stick landings, I heard it is kind of a brick.

thanx

Just be sure to use the choke adaptor with that engine (TT FS .91), or use a pump. It will not draw fuel well without the choke adaptor.

I just installed the choke, the engine is on the test stand, but I'm waiting to get a tachometer to start it. Any suggestion for the break-in?

thank you

Follow the instructions, except that a very rich mixture for the first run is more like 4-5 turns out instead of 2 1/2. Keep the speed at or below 5,000. You will need to keep the glow driver on to do this. Run it so rich it almos quits then lean it out just a tad. After than keep leaning it out till you have burned several tanks, then you can set the low speed and idle mixture.

Now, Since this is my first 4 stroke, I ask you to be patient.
The TT engine manual is not very clear to me, I downloaded the OS 91 FS manual and things are a bit different: full throttle for 5 seconds at max rpm, then slow down by opening the needle valve. Seems that the Os breaks-in with a 10 seconds alternate process of closing and opening the needle valve at full throttle! . In the TT manual no mention is done about throttle setting, it just says to not exceed 5000 rpm in the first five minutes… does it mean I have to run at full throttle for the first 5 minutes checking not to exceed 5000 rpm? Or should I throttle up and down for the first tank of fuel not exceeding 5000 rpm… uhm.. Please help me understand the correct procedure.

Thank you
david

The TT uses a harder steel sleeve so it can quickly wear out the rings if the engine is run up right away. Check out the Saito site and look at their manuals, 4000 speed at start up. That is because they use a chrome sleeve which is even harder than TT's. So follow the instructions as given by TT.