my little china girl motorized bicycle

motorstumpy

motorstumpy

New Member
So im woking on a parts list and budget for a new bike build. This will be my third. It will most likely be a walmart or yard sale mtb or fixie and a china girl motor. I have some questions that im hoping the great welth of knolage on this forum can anwser...

First what is the life expectancy for one of these motors? I did the rough math and if I use it as my main commuting method iI will be logging about 7500 miles a year. This seems like a lot when you consider I am basically at WOT most of the time.

Second what are the best mods/upgrarades/service I can do extend this? I am thinking of the following: all ss fasteners, remove or upgrade chain tenisoner, adding a billet sproket mount on rear, fancy synthetic 2stroke oil, upgraded throttle, reed and/or extended intake, and upgraded exhaust. The intake and exhaust I hope will increase power so that iI don't "have to" run wot to keep pase with traffic. However they are the most expensive so they may not go on first thing.

Thanks folks!usflg
 
Re: my little china girl

I'm not super experienced yet at this hobby, but my thought would be upgrading the bearings and having the crankshaft balanced to increase longevity of the engine. The better performing CDI's supposedly help out also by more accurately timing the spark to tdc to eliminate detonation, which would have a long term effect on durability. As far a performance upgrades. Better exhaust and port matching to let it exhale better and carburetor and intake upgrades, to include either plenum intake or reed valve and piston ramping so it inhales better. For chain tension, my technique was to shim the back side of engine mount to fine tune chain tension, then I'm using the chain tensioner from a fellow member on the forum to take up the little bit of slack there is. His chain tensioner is pretty impressive.
 
Re: my little china girl

I wouldn't try to keep up with traffic. Remember it's a bicycle with an engine on it.
 
Re: my little china girl

Best thing you can do to prolong engine life is to ride it like a tiny bicycle motor and not like a motorcycle.
I have had great results on several of my chinagirls, one I sold recently had well over 10k miles and still running strong!
In my opinion, one of the reasons I have so few durability issues is my riding style. I don't try to act like I'm on a motorcycle. I just putt along where the motor is happiest rather than trying to wring its neck all the time.
 
Re: my little china girl

By the sound of it I guess the best way to prolong engine life is to be "nice" to the ole' girl. By this logic if in increase power production to the point that I don't have to kick her in the ass so much then I should see a longer life span.

So I guess the intake and exhaust porting, expansion chamber and reed are the way to go along with taller gearing.

Will this work or am I way off base?

Can anyone point me in the direction of some porting instruction?
 
Re: my little china girl

motorstumpy said:
By the sound of it I guess the best way to prolong engine life is to be "nice" to the ole' girl. By this logic if in increase power production to the point that I don't have to kick her in the ass so much then I should see a longer life span.

So I guess the intake and exhaust porting, expansion chamber and reed are the way to go along with taller gearing.

Will this work or am I way off base?

Can anyone point me in the direction of some porting instruction?
Click to expand...

Plenty of information here on the forum for porting, if you're adventurous and skilled enough to take on the task yourself. Lot's of vendors here also if you want to just purchase the jug, and piston. Gearing? More teeth = less top speed, better take off and acceleration. Less teeth = more top speed slower take off and acceleration. Whatever suits ya.
 
Re: my little china girl

i have a china girl with about 2000 miles runs like a charm. i don't beat her but i don't baby her either,it all depends on my mood for that day.it's a 49cc motor also no mods on motor just an upgraded rear wheel. they are like women treat them with kindness and respect and they will hang around for a long time.
 
Re: my little china girl

i 've driven mine 22 miles a day from the last 6 months, i use the breakdown lane on the side of the highway and run wot the whole way, that's over 2600 miles and still running strong
 
Re: my little china girl

maniac57 said:
Best thing you can do to prolong engine life is to ride it like a tiny bicycle motor and not like a motorcycle.
I have had great results on several of my chinagirls, one I sold recently had well over 10k miles and still running strong!
In my opinion, one of the reasons I have so few durability issues is my riding style. I don't try to act like I'm on a motorcycle. I just putt along where the motor is happiest rather than trying to wring its neck all the time.
Click to expand...
Ditto: Too many guys want motorcycle performance from a tiny little engine strapped to a bicycle. In my opinion there is too much emphasis applied to increasing horsepower/speed and not enough on the important aspects which are brakes, bearings, wheels and frame integrity.
It's a motorized bicycle. Don't forget the second word; Bicycle.

Tom
 
Re: my little china girl

I wouldn't consider a sustained 30mph, motorcycle performance... 45-50 heck yeah.

All that aside what would you guys do to increase power production and minimize stress on the enigine?usflg
 
Re: my little china girl

Stumpy, if you choose to go with the chain tensioner, contact turbobuick1 here on the forums. He offers an EXCELLENT one that mounts right over the clutch actuator cover.

tensioner001Small.jpg


I have one and it has worked FLAWLESSLY. No worries about it falling into the spokes. Order directly from him here and he includes the metric Allen wrenches. Nothing else to buy. Best 40 bucks I ever spent.
 
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Re: my little china girl

paintgun said:
Stumpy, if you choose to go with the chain tensioner, contact turbobuick1 here on the forums. He offers an EXCELLENT one that mounts right over the clutch actuator cover.

tensioner001Small.jpg


I have one and it has worked FLAWLESSLY. No worries about it falling into the spokes. Order directly from him here and he includes the metric Allen wrenches. Nothing else to buy. Best 40 bucks I ever spent.
Click to expand...

I'll 2nd your motion on Turbobuick's chain tensioner. I got one too. I haven't mounted it yet because it's been too damn cold to even work in the garage, but it's a very well made piece. He's also just a great guy to do business with.
 
Re: my little china girl

A tuned pipe and 36 tooth sprocket are the mods I use to get my low end and cruising rpm's right where I want them. Less revs = more miles and less vibration!
 
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