Hi, I'm about to start construction on the Great Planes Ultimate bipe kit. I was wondering if I could draw on past experiences when it comes to recommending an engine. The kit calls for up to a .80 4-stroke. My question is what do people think about me installing a .91 4-Stroke (a Saito of course)...

Thanks for your replies...

Mike

Mike, I would think a .72 would be more than enough power for this airframe. The .91 would be too much unnecessary weight.

If you are goig to go with a 70ish size 4s, may I recomend the YS .63. It has plenty of power and is easy on break in and running. I have been running one for a couple of months and am impressed with its power.

Dru.

Depends on the performance you want, and how heavy you build.

A 70 will give good performance, but I personally would go for the Saito 91 for real "unlimited vertical". Remember that a Saito 91 weighs less than an OS 70, and not much more than the Saito 72, so weight is not an issue here. YS 63 would also work well as blvdbuzzard said.

Sprink

I've never built a kit before, so I'm sure I'll tend to be on the heavier side. There's 3 real reasons why I want a Saito 91S. First, becuase of the perfermance it will give me, you can always throttle back. Second, I already have 2 72 Saito's in use in my Cub and Ultrastick, and I don't really want a third or want to use one of the one's I already have. Fianlly, the price difference is only $50Can between the 72 and 91S.

Mike

P.S. Saito is the only 4-stroke I'll ever own. They're light , they're beautiful (with they're individual valve covers), AND they're reliable.. What more could you want?

Mike,

I'm at the same stage...trying to select the "best" engine for this kit. I can't decide between the Saito 91 or 72. I'm leaning to the 72 because I think the 91 may just be too much for the plane. I also have a spare YS91, and I'm not even considering it because I "know" it's too much engine for this kit.

i have built so many kits, and i have not found a high performance plane that would fly well with what the manufacturer recomends. put the 90 or even a saito 100 on it. it will put a smile on your face. unless you just want to get in the air and back down.

The mid-size, Yellow Aircraft CAP 232 is waiting for the engine to be installed downstairs in my shop and it was about to get the Saito 80 when my flying buddy pointed out the weight and power difference between the 80 and 91.

According to quantummdoels.com the 80 is at 19 oz. and produces 1.3 hp. while the 91 weighs 18.3 oz and produces 1.7 hp. Any contest?

HEY MIKE I INSTALLED A TT91 4/STROKE IN MINE. IT BALANCED PERFECTLY. HAS MORE POWER THAN I WILL EVER NEED & UNLIMITED VERTICAL. MY ADVICE WOULD BE A 70 4/STROKE AS I FIND MYSELF FLYING AT 1/4 THROTTLE MOST OF THE TIME.

ED

IF you have a computer radio, use negative expo on the throttle. I set up mine at around -50% so that the plane flies slower when level, but you have the power for vertical.

Have you ever tached an engine at "1/2 throttle"? I think you will be surprised at the rpm you get. My experience is it is around 2/3s not half. (eg 10000rpm max, 2000 rpm idle, you would expect 1/2 to be 6000. No, most engines will give about 7500)

Remember with a bipe it has more drag than a monoplane.

Thinking of putting a Saito 91 in my GP Cap 232.

I'm going with a YS63FZ...