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Old 02-15-2012, 01:17 AM
5-7HEAVEN 5-7HEAVEN is offline
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Join Date: Aug 2008
Posts: 1,912
Default Re: what did you do to your motor bike today?

Originally Posted by Skarrd View Post
I'm running a 7 speed cassette. i'm gonna switch it to my 34t 1st gear one which will give me 24.93:1 in 1st.

running a 24" tire, that will put me at
1st=17.2 mph at 6000 rpm 34t 24.93:1
2nd= 24.3mph at 6000 rpm 24t 17.60:1
3rd= 26.6mph at 6000 rpm 22t 16.13:1
4th= 29.2mph at 6000rpm 20t 14.67:1
5th= 32.5mph at 6000rpm 18t 13.20:1
6th= 36.5mph at 6000rpm 16t 11.73:1
7th= 41.7mph at 6000rpm 14t 10.27:1

I've heard these motors can reach 10k rpm range, and from the design i've seen i'd say that's rather feasible. the cylinder has 4 transfer ports (two large ones on the sides, and 2 small auxiliary ones opposite of the exhaust port.) not to mention the crank case is amazingly tiny compared to the china girl's crank case.

i'm also thinking that since these little motors put out 3-ish horse power that it shouldn't have much of an issue with running it like this.
JMO, I think you're in for a disappointing ride with those gears. You will definitely know this when you're stopped at the bottom of a steep ramp or hill, and try to climb it.

Ask me how I know this.

With a 3-ish hp 10,000rpm engine, you'll be making less than 2hp @ 6,000rpm.

If your engine has 10,000rpm capabilities, you'll be shifting @ 10,000rpm, not 6,000rpm. No one shifts 4,000rpm short of the redline.

My 2.8HP Tanaka 47R engine is rated @ 7,000rpm redline. With the pipe, I'm shifting @ 8,000rpm or a little less. If I'm putting around, I shift @ 5500rpm.

Here's how your gearing works @ high rpm.

First gear.....22.9mph @ 8,000rpm.....28.6mph @ 10,000rpm.
Second gear.....32.5mph @ 8,000rpm.....40.6mph @ 10,000rpm.
Third gear.....35.4mph @ 8,000rpm.....44.3mph @ 10,000rpm.
Fourth gear.....38.9mph @ 8,000rpm.....48.7mph @ 10,000rpm.
Fifth gear...43.3mph @ 8,000rpm.....54.1mph @ 10,000rpm.
Sixth gear.....48.7mph @ 8,000rpm.....60.9mph @ 10,000rpm.
Seventh gear.....55.6mph @ 8,000rpm.....69.5mph @ 10,000rpm.

You will run out of road in second gear.

In comparison, here's my gearing @ 7,000rpm redline and 8,000rpm:

First gear.....12.1mph @ 7,000rpm.....13.9mph @ 8,000rpm.
Second gear.....15.9mph.....18.1mph @ 8,000rpm.
Third gear.....17.9mph.....20.5 @ 8,000rpm.
Fourth gear.....20.6mph.....23.6mph @ 8,000rpm.
Fifth gear.....24.3mph.....27.7mph @ 8,000rpm.
Sixth gear.....27.5mph.....31.4mph @ 8,000rpm.
Seventh gear.....31.7mph.....36.2mph @ 8,000rpm.
Eighth gear.....37.5mph.....42.8mph @ 8,000rpm.

Last edited by 5-7HEAVEN; 02-15-2012 at 02:19 AM.
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