Would a Seagull Super Star 120 ARF be compatible with a ryobi 31cc?
Specs
Wing Span: 69.3 in (176 cm)
Overall Length: 62.6 in (159 cm)
Wing Area: 846 sq in (54.6 sq dm)
Flying Weight: 10–11 lb (4.5–4.9 kg)
Engine Size: 1.00–1.60 2-stroke; 1.20–1.80 4-stroke
Radio: 6 channels w/6 servos needed

The Ryobi 31 is a long engine. You would need to cut back the firewall so the prop would be in the same place it would be with a 120 engine. May have to make up something to extend the cowl or fuselage behind the cowl?

Enjoy,

Jim

Depends on what you want to do with this plane. I wouldn't think it's a good engine choice for the Superstar. I'm running a Saito 150 and it's about perfect thrust/speed. Maybe something like a Brison 2.4 or something.

One of these just sold for $152.00 on ebay & I lost out in the last 15 seconds for a couple of dollars.

Man,, what a steal !!
Have you noticed the almost total lack of interest in this plane bjmjs ? I started to post a full build review when I got it but from the total lack of interest I ended up just doing a short thread and a few updated modifacation posts. Funny part is , this plane is a great flying ARF. Tracks better than an Edge and is easier to handle than an Extra. The more I fly it the better I like it.
Sure it may look odd to many. But I like having something that doesn't look like every other plane at the field.

Sturtz: How about some close up photos for us old folks!!! HA! Capt,n

Here's a couple of shots before I got the CF landing gear .

Sturtz: Is super Star Arf 120 a well built plane? Do you think a 25-30cc gas engine would work out on this plane? Does it have plug in wings? Thanks Capt,n

Yes to all questions Capt. The cowling area is perfect for a side mounted muffler and carb stack. The Brillelli GT25 with CH Electronic ignition would be a good one. Maybe a Brison 2.4 , etc.
The plane is built very nice . Like higher priced ARFs. It has a great two piece wing system with alum tube and four 1/4" nylon wing bolts that have convenient thumb tabs.
I have a thread over in the ARF section on the one weak spot the plane has. Even got some pics how to beef it up. Easy fix.

Isn't the wing area to small for a 2.4 brison????

The wing area is small compared to a few other 3/D type models. I noticed Horizon had the 180 Saito listed at first as an engine choice then changed it to a 150 Saito and the little Evo 26 gass engine they sell.
On the other hand I've seen the Brison 2.4 in action many times and wouldn't worry about mounting it on one of these at all.
Weight is always a factor with a gasser. Bet this thing would scream with an OS 160FX.
Plenty of room in these cowlings for sure.