I modified my 115 v4 by swapping the heads to 130’s This increased the compression rating so the timing has to be retarded 2 degrees at WOT. I also bout an exhaust tuner and changed out the reed valves for carbon fibre. Unfortunately the motor needed a rebore so I went .005 over to specs. Finding 34 mm Venturi carbs was a struggle but managed to get them in the end. The exhaust port chamber is polished to a high finish but I doubt it gives any extra power, just better flow. I don’t have a dyno to figure hp rating but I run a 13.75 x 23 p on a Ring 20 and it has loads of mid range grunt . Top speed 62 mph flat
