Everything I've seen spec wise on these engines shows them to be HP rated at 5000 - 6000 RPM's, and as for the # of rings on the piston having 2 rings is twice as many as many of the smaller 2 smokers have as far as weedeater type engines and such go, they mostly have only 1 piston ring which works great and reduces friction/drag in the cylinder.
The vibration is due to being poorly balanced, some of the chinagirl engines are better than others but just like the rest of the stuff, you never know if you will get a fairly smooth running one or one that will numb your butt and hands at 3/4 throttle, mine all vibrate at very high WOT RPM's but with 36T sprockets or smaller they will all cruise real nice at 30-34MPH with minimal vibes that are still fairly comfortable for long rides of 15-20 miles, main thing is to just have them mounted very securely and tweak and tune them real nice, you will have a thing of joy when you do, I have a 150cc scooter that will cruise at 50 - 60MPH, I have a 1982 Yamaha XJ650 Maxim that will run a hole in the wind and I still love to just hit the back roads around here on my MB's, there's just something about the MB's that give such a good feeling and a sense of satisfaction from cruising around on something that is different than most people have and something you have put so much time & effort into getting right.
As to the comment I made about the 10K RPM's I was just throwing that out there......I'm sure he isn't actually turning those kinda R's....
Yep, lots of trial and error is part of the fun on these MB's, thank goodness we have this great forum to help us skip over a bunch of the ERROR and let us do many of our trials with a good amount of valuable knowledge to help us get many things done and fixed without to much grief most times.
As to the "Chinagirl or my Grubee Whingding 4-stroke" just depends on what you want, 2 stroke a bit louder, not quite as smooth probably, but more power and speed OR 4 stroke, smoother, a bit quiter, less power, less speed, but probably more dependable from many peoples perspective.
I dont own one of the 4 strokes so I cant speak from personal exper. but I have some very reliable 2 stroke china girls that I will jump on and go 50-60 miles round trip on and never have a worry in the world about getting back home under power from the engine and NOT the peddles.
Best wishes for what ever you go with, they both have +'s & -'s like everything else.
Originally Posted by Scootmeister
Hey Mapbike. I have a Chinagirl and was wondering how she's rated as far as RPMs. Does some brands rev higher? Recently I rebuilt mine and was surprized to find that it only has two piston rings instead of three. Why do they vibrate so at high RPMs? My Homelite bike is smooth at 7K. Must be a balance issue with the crank. Anyway, I was thinking about your comment to Atombomb and don't see how one of these engines could turn 10K when my Honda Nighthawk with 4 big Mikunis doesn't. Anyway, half of the fun of building these bikes is learning what makes them work best. I'm on a new project and I'm trying to decide whether to go with my Chinagirl or my Grubee Whingding 4-stroke.