I have been modifying the manifolds on my various Four Stroke motors to simulate the method used on all Laser Engines. I have never understood why one needs to have a sharp bend bringing the carb down behind the cylinder. It becomes inaccessible and in the hottest place. All my tuning experience on racing cars and motorcycles tells me to have the straightest path from carb to inlet valve.
Can anyone explain why Four Strokes are designed this way apart from bringing the carb up to tank centre when inverted?
By machining a short stub manifold, with the same bore as the original, I place my carbs straight on the head. Usually coming out just at the rear of the cowl on side mounted installations. Easy to finger choke, easy to set the slow needle and appear to run without any problems, probably slightly more power at top rpm. One of my engines is the RCV 58, a good engine now even better!