China Girl Motorized Bicyle Build

GoldenMotor.com

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

Time to start accessing the build performance.

It has about 200 break in miles I think, but I've kind of lost count. I'd caricaturize it as a brutal break-in so far. The cylinder has been off it twice since the initial completion. There was a small end bearing failure at 150 miles, and a base gasket failure about 50 miles later. Because of this insolent behavor I've beed whipping it like an ugle step child. Oil ratios have been all over the place, but always with good oil. At least one tank may have been as little as 40:1, but usually more oil than that.

I think fuel consumption is around 50-60 miles per tank now. It was guzzling the stuff till I jetted down to a tiny little 62 main jet. With a 66 I was getting 35 mile per tank.

Engine sprocket 10T rear wheel 36T

It's geared for 5.17 mph per 1000 rpm

I don't think we can ask much more than these kind of engine speeds. I'm thinking 7500 is pushing it, but this is for science.

I weigh, OMG 220 lb. I'm going on a diet tomorrow I promise.

This is what I'm seeing after a good long warm up.

16 mph = 3095 rpm, slowest cruising speed. fair power, good full throttle pull
20 mph = 3868 good smooth power
29 mph = 5609 rpm starts a slight flat spot
31 mph = 5996 rpm starts running like wild monkey above this speed
35 mph = 6770 rpm, I have to keep letting off the throttle to maintain this speed
38 mph = 7350 rpm will easily do on a flat
39.9 mph = 7718 top speed on a flat laying down
42 mph = 8124 rpm fastest speed so far on a downhill. Insane speed for a little china girl, but it's in the name of science.

This is the Cadillac's calculated speed to RPM.


RPM MPH
1000 5.2
1200 6.2
1400 7.2
1600 8.3
1800 9.3
2000 10.3
2200 11.4
2400 12.4
2600 13.4
2800 14.5
3000 15.5
3200 16.5
3400 17.6
3600 18.6
3800 19.6
4000 20.7
4200 21.7
4400 22.7
4600 23.8
4800 24.8
5000 25.8
5200 26.9
5400 27.9
5600 28.9
5800 30.0
6000 31.0
6200 32.0
6400 33.1
6600 34.1
6800 35.1
7000 36.2
 
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killercanuck

New Member
Dec 17, 2009
1,748
6
0
47
Wallaceburg ON
Re: China Girl Motor Build

nice, the lower the cruise speed the higher the mileage, eh? Thought about dropping the rear sprocket a few teeth, or a shift-kit? Shift kit will let you haul up the hills in granny-gear, yet still let you fly at 40 when you want. Great info up there!

Good luck with that diet. :p
 
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biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: China Girl Motor Build

I just wanted to say thanks for the great video, music was good and just and all around great little short video, beautiful bike man........I really like the Cad-E, Clean, slick, shiny and just plain nice.......once again, good job biknut.

Peace, Map



I think it's still running rich. The plug is dark, and I only got about 35 miles before the tank ran dry. Right before it ran out, I thought it was running even a little faster, but not for long. I ran out of gas and had to peddle the last 5 miles home lol. I needed the exercise though.
 

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

I just wanted to say thanks for the great video, music was good and just and all around great little short video, beautiful bike man........I really like the Cad-E, Clean, slick, shiny and just plain nice.......once again, good job biknut.

Peace, Map
Thanks mapbike. The Cadillac is really starting to show it's worth. This motor is sweet but it's still running rich.
 

rustycase

Gutter Rider
May 26, 2011
2,746
5
0
Left coast
Re: China Girl Motor Build

Gosh what a nice looking motorized bicycle, B!
I like it!

I'd like to ask abt your camera mount.. the video was great!
Is your camera back-pack mounted, or rack mounted?

It works very well!


About the jets... how does your number system work?
When I re-jet mine, larger numbers are a finer (smaller diameter) bit.
... a #64 would be FAR larger than a #70 ...

Is there some different numbering system on your jets from the factory?

I'm using fine-wire number drills...

Tnx
rc
 

nightcruiser

New Member
Mar 25, 2011
1,180
2
0
USA
Re: China Girl Motor Build

About the jets... how does your number system work?
When I re-jet mine, larger numbers are a finer (smaller diameter) bit.
... a #64 would be FAR larger than a #70 ...
I am pretty sure jets are sold by the size of the opening, so larger number would have a larger hole. Drill bits that would be used to make the holes larger, however, are just the opposite, the larger the number the smaller the bit....
 

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

Gosh what a nice looking motorized bicyle, B!
I like it!

I'd like to ask abt your camera mount.. the video was great!
Is your camera back-pack mounted, or rack mounted?

It works very well!


About the jets... how does your number system work?
When I re-jet mine, larger numbers are a finer (smaller diameter) bit.
... a #64 would be FAR larger than a #70 ...

Is there some different numbering system on your jets from the factory?

I'm using fine-wire number drills...

Tnx
rc
LOL, I mounted my GoPro HD on a stick that's supposed to go to my wifes car wash brush. It's aluminum and extends to about 3'. I used a couple of hose clamps and attached it to the rear rack. I wore a bungie cord that holds it close to my back, and acts like a shock absorber to keep the stick from bouncing around too much.

I'm using actual Jets from SBP. In this case the smaller the number the smaller the jet size.
 

Bmoney

New Member
Apr 20, 2011
25
0
0
Sterling, Ma
Re: China Girl Motor Build

I just read through your entire thread, not joking... I love your bike! and your passion for these ht engines! You've motivated me to tare down my extra engine to start re-building it.
Ill be checking in for more updates
 

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

I just read through your entire thread, not joking... I love your bike! and your passion for these ht engines! You've motivated me to tare down my extra engine to start re-building it.
Ill be checking in for more updates
After very little practice, these motors are easy to master. I'll keep an eye out for your rebuild.
 

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

I dropped the jet down to a 60. One test ride so far, and it seemed to run better all over. I'll post more about it after futher testing.
 

biknut

Well-Known Member
Sep 28, 2010
6,632
411
83
Dallas
Re: China Girl Motor Build

I'm pretty happy with the 60 jet. My spark plug is sort of reddish looking. It runs dry as a bone too, with 50:1 ratio. Because of that I decided to go 40:1 for a while to see it I like that better.

There doesn't seem to be any difference in power on the top end from the 62, or 64. It's possible I may have even lost 1 mph but hard to tell. The throttle response is great all through the power band. I haven't got enough miles on the 60 jet yet to tell about the gas mileage, but it has to be a little better. I hope I can get at least 50 miles per tank. Starting is noticeably harder than when it was running rich, but I'm still starting with no choke.

This is as lean as I'm willing to go, no matter the mileage. I've ridden it far enough now at WFO to seize it up if it's going to, and it didn't. I probably need to keep a closer eye on the cyl head temperature now.

I really don't understand why it likes such a small jet. Must be the MM head I think. All my other 80s liked a 68, which ran slightly rich, but got good gas mileage.

After I get good and used to the way it's running now I'm going to try a different carb. Either a Speed carb, or my RT.
 
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