More strokes =more problems! Ha .I can run a fully built 131 Sudam or a 250 cheaper than an open modified 14.5, and have twice the reliability and HP with half the maintenance. More strokes = more problems! Ha
The CRE6 is a great pipe, run them on 131's and a couple 150's.I would recommend an S4 or CRE6 for a gas 125. I know they’re 100cc pipes but they’ll balance out that motor a good bit. You could try a KB06 but you’ll get a ton of bottom end and I’m not sure that’ll help.
2 short, what ever that is for the pipe you're using and the engine you're using, can cause the engine to go lean. Been there, done that. It's my experience; pipes have a "perfect" header length, that length can change plus/minus a quarter-inch very safely, much more than that and you start running into less performance and/or a lean condition. If you have no information on that perfect length, practice laps will help. You have a stopwatch right?Just keep in mind, shorter flex, more heat. More flex for bottom end and less heat, less for more top end at the price of more heat. However temperature is almost a non point for H20 motors, even on gas. If you’re sticking a piston on an H20 motor and think flex length is to blame... you have bigger problems.