I have a PK80 right now on my murray westport(heavy bike/ heavy rider). It has nice pickup through 7mph to 15mph+. Then once I get over 20mph I can blast it up to 35+ like a good motorbike should. It really opens up when you get rolling. My fastest speed so far is 46mph on a flat stretch. Its almost like a new beast, but I can only compare it to my friend's 33cc which is less than half my engine if you compare HP and Torque. Good luck and make sure you put on some bigger brakes, I've already upgraded to front disc. Still have rear pull, but will be adding a rear disc when I install SBP's shift kit. Hands down the disc brakes are better all around. L8R!