I know this has been covered before and please excuse me reopening the subject.
I have a SIG Four Star 60 ARF.
I have the following engines:
Magnum .61 2 stroke
Magnum .91 XL 2 stroke
OS .70 FS surpass 4 stroke
Which one would you recommend for this plane? (or should I buy another one?)
Note: the Magnum .91 has a pitts muffler, I don't have the original muffler and am not sure if it will fit properly.

either one of the magnums. The 91 would probably be a tad too much, but it's better to have more than you need than need more than you have. Just check your CG before you're done. If all else fails, use the .61. You'd probably have to move less to achieve your CG.

I'm putting my OS .70 FS on mine; I'm still building it. The plans show a Saito .65, and the OS is comparable. I know it is unfashionable to consider the designer's recommendation, but a couple of posts elsewhere say the plane actually flies very well on the 70 FS and has plenty of power. Don't use the .91 unless you are experienced enough not to need recommendations. Jim

A 70 four stroke on a 60 size plane (are you sure you're not talking about the 40 size)? I would think that would be slightly under powered. Go with the 61 two stroke, unless you balance better with the 91.

I have a Saito 80 on mine and I very rarely have the throttle above half while in flight. Plenty of power. I would think an OS 70 would work just fine. Good Luck, Dave

Here is a perfect opportunity to buy yourself a new engine!

The Tower Hobbies .75 is on sale right now (Sterling reputation!) for $89.

I mounted a GMS .76 on mine.

Thank you all for your input.
Yes I do need all the advice I can get (I have yet to solo my trainer so it won't be until late summer before the 4* flies "with some luck")
I did come up with yet 2 more options.
Super Tiger G90 and Magnum GP65 SE (older one made by Thunder Tiger)
I have read reviews that say the 4*60 is tail heavy so maybe a bigger motor would be the ticket (better than dead weight?)

A magnum 91 four stroke is a great engine for a 4*60. with a magnum 91FS you will not need to add any extra weight to the plane and it will give you good reliable performance for a good price

I put a Saito 100 on mine.

I have a TT.91RFS on mine swinging a 14x6 APC prop. Perfect combination. I'd think a 70 four stroke might be a bit too small, plus the weight of the 91 prevents the need for any added nose weight. Mine balances perfectly.

Good luck.

Saito 72 on mine

Enya 90 four stroke on mine, but what you have is fine...go with the Magnum 90 or ST 90 - yes the Four Star 60 ARF IS tail heavy. While the 4* 60 is very well suited to a four stroke engine, note that a 70 size 4c is at the low end of the engine requirement. I'd stick with the two strokes unless you come up with a 90 size four stroke.

I put the Thunder tiger pro 61 and an apc 13*4 wide and it will hold a hover with this combo, good power and thrust as well. A two stroke 75 would be sweet though... This is actually my first post on rcu in over a year, the only reason I am here is because I'm leaving the hobby and am sadly looking up how much four stars go for these days rtf.
You will absolutely love this plane either way you go, just don't use the 70 fs unless your content with flying circles and the occasional aerobatic move as it will be underpowered.

All of the two strokes you've listed will likely be very similar in weight. The majority of .90 and .91 two strokes are just bored out .61s so the weight difference, if any, would come from the bigger muffler on the bigger engine. SIG estimates the weight at about 8 pounds. The 70 four stroke should pull it around well. No hovering or other 3D stuff but 4*s are not 3D airplanes. For graceful basic aerobatics any engine you listed would be fine.

i used a super tigre 75 on mine.

I put a Saito .91 on mine and my friend used a Magnum .91 on his, both planes were tail heavy. We both used 14X6 props. Good luck the Four Star 60's fly great.
Here are a few links to mine.

http://putfile.com/pic.php?pic=4/10317384644.jpg&s=x402

http://putfile.com/pic.php?pic=4/10318300443.jpg&s=x402

tower hobbies .75 on mine still took 4 1/4oz weight up front to cg but has great performance. fly mostly around 1/2 to 3/4 throttle with full throttle it has great (not unlimitted) vertical hoping to take mine out later on today.