ORIGINAL: darock
I know a 91 or 100 FS would probably be beffer,
Better? how?
Heavier
Cost more
Might have prop clearance problems
Require more maintenance
Harder to adjust needle settings
Require higher nitro, higher priced fuel
Require higher priced glowplug
No, actually fourstrokes aren't better. Best case they simply do the job differently. But at a cost in money and effort.
Simple rock... Because it's a 4-stroke!
Heavier? yes
Cost more? Yes, but then, you get what you pay for
Might have prop clearance problems? I've never had it happen yet
Require more maintenance? This is a myth. I have had to adjust valve clearance once in my life (And I've been using 4-strokes for over 15 years)
Harder to adjust needle settings? Why, did you have a stiff one? They are no more difficult to adjust than a 2-stroke.
Require higher nitro, higher fuel price? Yes, but an OS 91 surpass will burn about half of what a 60ish 2-stroke will burn - and it won't slobber goo all over your airplane in the process.
Require Higher priced glowplug? Yes.
So really, only two of the points you made (The first and last) are valid - They are heavier, and the glow plugs cost more
The next 4 points are really irrelevant, and as far as fuel goes, I don't care if I have to use 15% nitro instead of the 10% I used to use, I burn so much less that it is worth every penny.
AND I don't have to wipe half of it off my plane after each flight!