Top Speed ?

[Toby woodman]

I have a stock Chinese engine. it's running a stock bofeng carb with no tuning or jetting apart from needle clip adjustments. I am using a 26inch wheel and a 44 tooth sprocket. is a top speed of 32 mph what this engine should be capable of. if this is how fast it goes stock with some tuning, upgrades and a smaller sprocket. what sort of speed could I expect.

 

[DAMIEN1307]

I have a stock Chinese engine. it's running a stock bofeng carb with no tuning or jetting apart from needle clip adjustments. I am using a 26inch wheel and a 44 tooth sprocket. is a top speed of 32 mph what this engine should be capable of. if this is how fast it goes stock with some tuning, upgrades and a smaller sprocket. what sort of speed could I expect.

More than likely, somewhere in the low to mid 40s MPH range for most folks...You will lose a little in low end torque though.

 

[Toby woodman]

thanks. what speeds do people usually get from a stock engine

 

[DAMIEN1307]

thanks. what speeds do people usually get from a stock engine

32 to 38 MPH on the average if put together properly and a reasonably tuned carburetor via needle adjustment in most cases.

I wouldn't be going any smaller than a 36 tooth sprocket though.

 

[GW's Motorized]

Weight is a factor. But like Damein said, 32 to 38. People are able to coax 50 mph out of these engines, but staying there for long is not a good idea.

 

[DAMIEN1307]

People are able to coax 50 mph out of these engines, but staying there for long is not a good idea.

When I had my Zeda 80, I was able to "coax" 50 MPH but that was max, but never for any sort of prolonged use, I only tried it a couple of times just to know it would do it, took me way out of my comfort zone of 30 to 35 MPH cruising speed which is what I prefer to travel at.

The Phantom 85 I have now is quite the other story though...It just wants to GO...lol...Easily hits 50 with throttle to spare but I still stay at 1/4 throttle for my usual 30 to 35 MPH.

Ps...And thats pretty good since the bike is 80 pounds and I am 217 pounds of pure, unadulterated, lard butt...lol.

 

[ImpulseRocket]

With a 44 tooth sprocket on your setup, 7000 rpm = 30mph 8170 rpm = 35mph.

Those speeds are reasonable, and possible, with most motors after proper tuning on a motor that isn't a total dud out of the box with crappy ports.

With a little mild tweaking - setting a good squish gap, mild port work to and port matching on the intake and exhaust, internal transfer port transitions, etc., and a real MZ65 installed, a 66cc engine should have no problem reaching 40mph or close to. It may be a tall order with a 44 though, as you would have to surpass 9300rpm, which even with mild port work isn't going to happen. A 36 or 38 tooth will give you the room to achieve those speeds in the RPM range of the engine better, but at the cost of acceleration and hill climbing ability.