I got off work early to go to the doctors for a quick check up. Stopped at the Hobby Shop and picked up some fresh fuel and headed home to put some more breakin time on my Saito 40A. I was thinkin I was pretty nifty being able to start my engine just by back flipping the spinner against compression. Got everything setup as usual, backed the spinner against compression and boom it was running. Immediately I realized it was running backwards, it was sucking fuel into the muffler and exausting out the venturi. Now some of you have spoke of this but I have never seen it and I have a lot of years of four strokes in RC. You can't just pinch the fuel line off as usual to stop the motor "you have to pinch the muffler pressure" line to stop it. ASK ME HOW I KNOW..........I had it shut off in less than 10 seconds. Note the fuse is burn blasted from the hot exhaust coming out the venturi. Also note the VENTURI hanging down by melted strands of delrin the Venturi material. It just melted and fell off in 10 seconds or less. For me this was scary sh_t. I will use the starter from now on to make sure it's always running in the right direction. Go ahead ask me why my knees are knockin. Once the paint was blasted off it was blowing against the ply. If this had been a full bodied job I would of never got it shut off as quick as I did as all the lines are hidden. Who knows? 
                    

Thanks Bob,
As I told Doug Moon I never thought to put my finger over the exhaust as I was operating in panic mode and putting my finger over the exhaust goes against my normal logic. Thanks again and let me know if theres anything I can do for you.

Here is something I do on all my 4S planes.

   1) I do not use uniflow. All my tanks are set up to vent from the forward inner upper corner.
    Consider this - If a 4S engines runs backward with a uniflow setup, the uniflow tube becomes the pickup
    since it is submerged. Remember, when running backwards, it is sucking air in through the muffler, which acts
    like a venturi..
    With my setup, the vent will suck in only air and the engine will not run.
    Besides, I have tried uniflow and non-uniflow on many 4s applications and I cannot find a difference.

   2) I use only metal tanks

    Bob Z.

Bob,
Insert arrived. Thanks you are the best.

Hi Bob,
Well it's easy to be out spoken on a forum where you never really get to meet the person and understand there feelings etc.
Anyway great ideas Bob. I will follow up with your advice on the flaps before I do any cutting etc. I got everything running again. As I was setting the tank height while running it in the garage I noticed that the upright and the inverted RPM's were the same but as the plane went vertical the RPM's dropped, but only in the vertical position. As I kept messing with it, the plane would be 10 degrees off of vertical and would be fine but as soon as it hit vertical the rpms dropped. I tried different RPM's and it always dropped. WEIRD.... Here's what I found. The tank I'm using is a plastic, clunk, Great Planes tank and the rear of the tank is designed so it's concaved, yes, it go's in approx. 1/8 to 3/16 of an inch. So when you look at the clunk it looks like it has plenty of clearance but when it goes vertical the end of the clunk was getting blocked off enough to slow down the RPM's by the concaved end of the tank. I cut an 1/8 inch off the clunk line and now it runs smooth in all positions.