ORIGINAL: ro347
I too have questions about this. Working on a showtime with my first four stroke engine(Saito 91). Engine will be covered by the cowl. I have a T-fitting to place in line with the Needle valve to fill....
The needle valve line is usually the choice because the needle valve acts as a partial plug. However, four cycles often have bent tubes from the head to the carb, and those can catch every bit of fuel that fueling pressure pushes past the needle valve while pumping the tank full. It usually doesn't happen when the 4C is on it's side or rightside up. The tube is updraft and points down when right side up..... yeah..... so won't fill up except when pointing up. OR SOMETHING LIKE THAT!! [sm=wink_smile.gif] Anyway, your fueling technique can uncover the problem. If you wind up flooding the engine right off the bat, be prepared to either fuel differently or setup the plumbing differently or get yourself a hemostat.
but what about the overflow? Do I also "T" the muffler pressure line?
Best case is where the overflow line is reachable. And can be disconnected. But the overflow line has to do one thing for sure. It's got to be connected to the tank pipe that goes into the tank to the top, where the "over" is in the word "overflow".
The engine will be almost inverted....Head will face 7/8 o'clock postion. Can I just watch for overflow from muffler? Or will this cause issues starting?
Overflow in the muffler works if the overflow can hit the ground without having to fill up the muffler or such. If the pressure fitting doesn't have an almost straight shot at the ground, it's probably best to do the deed some other way.
Would I be better off using a 3 line system for filling?
T fittings in the pressure line, when it goes to the top of the tank usually work good as an overflow. You may waste a bit of fuel, but it beats how much you waste watching for fuel to pour out of the muffler.
T fittings in the delivery line usually work ok for filling. Needless to say, if you were to run a filler line into the tank that is capped when not filling, it'll solve any problems that happen with filling the tank through a T off another line. That dedicated line will need to go to a pipe in the tank that goes to the bottom of the tank for it to work to empty the tank at the end of the day. But beyond that, it's almost foolproof.