Hello
I am building a cg untimate and I think that I want to put a 120 size 4 stroke in it. I am currently looking at a ys sf 120 and a os 120 older version. Is there much difference in weight? What does the sf stand for in the ys engine?
Thanks for any advice.
Jeff

This is an age old question, but a good one. The YS designations have eluded even the best of them. You should do two things, (1) Do a search on the subject as it's been out there before, and (2) Ask the sf question in the YS forum. I know you'll get what your'e looking for there. As far as which one, it depends on who you ask. After using YS in my competition pattern days, personally I would use nothing else. They are a bit finnicky, but once set up they're flawless in performance and reliability. You need to be a bit of a tinkerer with the carb and fuel delivery system. It's not impossible, but can try your patience at times. They also tend to be a little heavier than most comparable engines of their size, but the performance often outweighs the extra ounces. Just my opinion and Happy Holidays_bob

Hi Jeff,
Have you thought of trying an RCS 1.4 gas engine in this airplane. It is a really light engine and will turn the same prop as the 4-stroke with a great savings on fuel costs. Check out the specs at their site.http://www.rcshowcase.com/ Good luck

fancman /jjoos99
I AGREE WITH FANCMAN
I HAVE THREE RCS- 1.4 . IF BROKEN IN PROPERLY THE POWER /WEIGHT
IS AWESOME THEY ARE LIGHT VERY POWERFUL AND RELIABLE, NO FLAME-OUTS. 16-8 MASTER AIRSCREW @9000 RPM . FOLLOW THE BREAK-IN, BE PATIENT. PJAMESRC JIM