I putting together a Super Decathlon and putting in a Saito 72 with 13x8 prop into it. If a person goes inverted is there anything special it should have or be done to it. This is my first 4c and can't wait to hear it. I've never even heard one other than on videos.

flynte

Mount it and fly it. Saitos run just fine inverted.

G'day Mate,
The only time you will have trouble with inverted motors, of any type, 4 or 2 stroke, is if you tank height is not right, that is needle valve on carby, level with, or up to 3/8" lower than the needle valve. It must be at the right height, because if it is too high, & that is usually the problem, the fuel will siphon into the carby & cause BIG problems, fuel lock & bent conrods & so on.
Another solution, if it is a problem getting the tank low enough, might be to have the motor at 90 degrees (side on) that way you muffler will exit under the plane, & help keep it clean, just a thought.

My tank outlet is about 3/8" above the carb on my my inverted S82 and she runs
great, You do need to keep it close to what Allen has stated above, I have seem
some at or over an inch and still no problems, But that's cutting it close to problems
more so for other engines.... Another option is to use a fuel regulator... Or a YS

Thanks for the replies. Looking at it, as this ones an ARF, the tank loaction is kinda written in stone with the way it's built and I'll end up with the carb to low. Has anyone ever had any problems with fuel regs, or are there better ones over others a person should watch for.

flynte

If you run an inverted engine and leave the tank in the usual stock position, your rolling the dice. Some guys say theres is fine and thats good for them. I suggest you don't and lower that tank because any problems you have with that engine IMHO is going to be directly related to your tank position. So you and your buddies will be needlessly screwin around with that thing but its your plane.

I'd heard that putting a small loop in the carberator line is often enough to prevent the syphoning effect that causes carburator problems. Can any of the veteren pilots reading this thread comment on whether or not this works? If the loop extends above the tank outlet, it would seem like a good, simple solution.

Yup,

Just make sure the line from the tank to the carb runs above the top of the fuel tank and yer golden. Fuel regs and pumps are overkill and more trouble than they are worth IMHO. If you plan on fueling your tank and waiting for an hour before flying while you BS with the natives, then...you're on your own. (Heat and pressure changes will defeat the small loop in the fuel line).

The loop will sort of work until fuel goes through... Once the line is full.. If it's
down hill, It's going to go IMO... If your tank is at the bottom of the fuse, not
much you can do about it, if not you can make some pretty easy mods to lower
the tank... On my first UCD I lowered the Tk. by 1/2 or so, by oblonging the
firewall and trimming the tank saddle. On UCD 46/S82 #2 I left the tk. as is,
but I installed the stock engine mount up right in the stock location and instead
of mounting the engine on the bottom of the mount I installed it on the top( had
to mod one of the mount arms a little to get the carb to fit, but it was very easy...
the cowl fit with no problems and it raised the carb. by about 1/2" And tho the carb.
is still a bit lower than the Tk... She works great... Good luck....
Saito's run inverted pretty good IMO with some adjustment.. On some of my models
I "lighty" close off the needle after fueling and left sitting then reopen when I'm
ready to go....

G'day Mate,
In this case too low is better than too high, of course it depends on how low, & I doubt that a decathlon fuselage would allow it to be too low. So check it out first.