China girl 66... Maximum RPM?

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I have had mine up to 8200 rpm seemed to smooth out and sound different .
 
So...5500 seems to be the manufacturers limit... good.
I wasn't far off, better to err on the side of safety with these little hand grenades.
Thanks.
BBB
I lifted the exhaust port on my 48cc and fabricated an expansion chamber tuned for 10500 rpm. Now it screams like a dirt bike. I've been commuting everyday since the modifications and have racked up 6000 miles at red line WOT (I abuse that engine). These engines are solid. all of the problems i have had with the bike were not related to the engine or the modifications i made. I have replaced the rings once but everything else in the engine is the same. so, yeah. Far from hand grenades lol
 
I lifted the exhaust port on my 48cc and fabricated an expansion chamber tuned for 10500 rpm. Now it screams like a dirt bike. I've been commuting everyday since the modifications and have racked up 6000 miles at red line WOT (I abuse that engine). These engines are solid. all of the problems i have had with the bike were not related to the engine or the modifications i made. I have replaced the rings once but everything else in the engine is the same. so, yeah. Far from hand grenades lol


yay, another advocate of smaller is better. always liked the 48's. the skyhawk, black with round fins seemed to be the best of the bunch.kept them stock mainly because once you have made a good pipe...its really easy to swap over.

as for the 66... meh. hard to comment when you only got one and it never was capable of even going 5 minutes without some type of issue. dodgy ebay junk engine, was listed as a 48.
 
45km/h with 56tooth /19inc wheels or 33 sprocket 72km/h its gonna make 9000rpm. carburator drilled 16mm, exhaust without cap and drilled, head -2,5mm and ported silinder 2,4cm wide and exhaus port 2,5mm higher. And you got "Race engine" what lasts about 50hours :D
 
I just did 36 kms at 55 to 66 kph with my Grubee GT5A.
It starts detonating at max speed and load, screaming for one of Jaguar's ignitions.

Here is the head before and after a wipe. Oil was a jug of unlabeled semi-synthetic I had on the shelf, 32:1.

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So how many rpm am I doing with a 44t sprocket and 26" MTB tires at 66 kph?

Steve
 
That's 41 mph!!! What have you done to your engine. 41 is winding out though I know that, I think I was hitting 7500ish around 37 with a 44tooth
 
I just did 36 kms at 55 to 66 kph with my Grubee GT5A.
It starts detonating at max speed and load, screaming for one of Jaguar's ignitions.

Here is the head before and after a wipe. Oil was a jug of unlabeled semi-synthetic I had on the shelf, 32:1.

full


full


So how many rpm am I doing with a 44t sprocket and 26" MTB tires at 66 kph?

Steve

2.8kph per 100rpm of the output sprocket.
410rpm = 100rpm at the output sprocket.
I get confused with direct drive, do this all the time for shift kit ratios, but I think it's 9664 rpm = 66kph (on 10:44, 26")
 
That sounds about right, looking back at my old thread about that and i said 34mph. I sense then bought a mzmiamiparts expansion chamber and it must be tuned for 7500 because as soon as i would max out old exhaust, my new exhaust would seem like it let the turbo spool lol she kept climbing and climbing but the very large turn kept getting closer and closer so I had to stop:D
 
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