[gitsum]

I have a Tomos Nitro 150 (made by SYM). The current weights are 13 gram rollers. The scooter is mostly stock, I just retuned the air screw a bit and increased the main jet from a #108 to a #110, removed and blocked of the PAIR junk.

This scooter really hauls @ss for a 150cc air cooled engine. Riding two-up (combined weight 260 lbs) it tops out at an indicated 65 mph and holds long grades at 50+ mph, acceleration is very spirited up to 45 - 50 mph on level ground. Accelerating at WOT the rpms are 6800, and at a steady indicated 55 mph (3/4 throttle) they settle down to 6400. I have a CHT gauge installed and temps usually run 310 f - 350 f (on a warm day), at cruising speed (indicated 50 -55 mph) and a long grade at WOT will push the temp to 370 - 375 f for a short time. The speedometer is about 5% optimistic. Averaging 90 mpg so far.

I'm really happy with the overall performance and feel like the CVT tuning is pretty close to optimum. I want to switch to Dr. Pulley sliders and keep the rpms close to the same, or maybe just a couple of hundred rpms higher. I've used Dr. Pulley sliders in my last 5 or 6 scooters and like the overall performance and extra longevity. Should I try 13 gram (same as stock) or 14 gram? I know a lot of GY6 guys like 12 grams, but I am afraid it might raise the rpms to 7500 or above and push me above the maximum torque band during WOT acceleration? This engine pulls good at 6800 rpms and really does well on hills, I don't want to compromise that or have the engine spinning at higher speeds with no improvement in acceleration.

My last 5 scooters were: SYM HD 200, Honda Elite 110, Yamaha C3, SYM DD50 two-stroke, Oliver City CPI 50cc two-stroke. All of them were modded and had the variator weights tuned, but I don't have much experience with the more common GY6 157QMJ.

Any opinions or advice would be greatly appreciated.