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Discussion in 'Motorized Bicycle General Discussion' started by rock out, Nov 4, 2013.
I will be putting a post in Swap and Shop one of these days with all the details.
your right about not needing reeds , i run that same setup
puch 70 hi hi
lots of well thought out porting and piston mods
long intake cns carb
home made x chamber
i still run a 44t so i fall in the mid 30 MPH range for speed and my bike is still reliable . and amazingly torquey lol
but with the skill i have i know for a fact that with the same money i spent on this kit and the upgrades and all the time spent porting/modding ..... i could have bought a brand new py 212 and a torque a verter and modded and mounted it in my bike and been like wow !!!! a degoverned 212 preddy with larger valves and port work and a roller rocker set ...( i own a valve cutter and reaming tools) would pull a well built china girl backwards and up hill !
Most of the china engine castings look like crap, bent and deformed fins, rough spots, slag and flash stuck to the casting, uneven seems, gaskets protruding out. Good news is aluminum is soft and cleans up easily. I've found that power tools / air tools tend to be better suited for roughing in your surfaces. I use hand files to do the finish work. Yes it takes longer but you won't have any "opps moments". It's a lot easier to take metal off than put it back on...
Wheelwoman is right about heating up the fins to straighten them, and being very careful with the amount of heat you use.
Here is another tip to control the temperature. Using an acetylene / oxygen torch with an appropriate size "rosebud tip" lightly coat the aluminum surface with acetylene soot (oxygen off), turn on the oxygen and heat up the bent surface. Keep the torch moving so not to concentrate the heat in one spot. Aluminum melts at 900 degrees and the soot will burn off at about 800 degrees. At this point the aluminum will bend easily before it melts. If you have little or no experience with a torch avoid a tragic disaster and find someone who does have the skills. Hope this helps...
Here is a link to a pic of a silver china girl I recently finished in black.
Ditto.......... very true!
Heating an entire cylinder with a rosebud tip could easily cause deformation to the cylinder bore or damage to the bore plating. I suggest caution with high temps on these poor castings...definitely something best left to experienced metalworkers.
There's no need to heat to a high temperature. If you're careful just heating the cylinder up slowly in an ordinary domestic oven will be fine (Oh it's so wonderful being the lady of the house). It's trying to bend the fins on a cold alloy casting that will mostly result in failure. Ease the fins gently, use smooth jaw pliers and it's useful to have them hot too. Oven mitts are the kitchen bench engine mechanic's best friend.
honestly i was not impressed with the stock kit ether, i bought a grubee gt5.
so i pulled it appart and researched, i ported as much as i could and as best i could to gain all around power then modded the piston by cutting the intake side 1/4in shorter and grinding ramps for the transfer ports and exhaust, wrist pin hole was drilled to 7.5mm to lighten it and i extended the intake to 7 in total, then i made an x chamber and installed the puch 70cc hi hi head, i hen pulled the clutch assembly appart and reasembled it properly lol.
after all was said and done the motor is a whole lot faster and rev's far quicker and higher and the torque practicaly trippled !! that being said it is still no where near as powerfull as even a stock 6.5 honda clone that can be had for 99$
knowing all the work the time and the money i spent getting the kit to be "better" and "more powerfull" i wish i could go back in time and buy a preddy 212 !
all i would do is have my fiance weld a nice mount for me so the motor sits vertical, then i would degovern the motor and install a custom intake manifold for the spare 21mm mikuni carb i have from an old honda 3 wheeler, then some simple valve mods like using my tools to cut larger 3 angle valves, then porting, then new valve springs rated for 8,000 rpms +, and wile its apart wile removing the govener system i will install a new cam lobbed for high torque and good midrange power, finaly 1:2 ratio roller rockers from NR racing (i have a set sitting in a box from my karting days) and decking the head for 11:1 comp , and aluminum flywheel with adjustable timing and finaly a sweet torque a verter or a bully disk clutch to a j shaft .
that setup would cost me only 100-200$ more than what i spent on the china girl and be well worth it in the long run !!!!
i would imagine it would be capable of speeds upward of 50mph and enough toque to pull any hill all in a reliable no fuss easy running motor.
if you have the skill this is the way to go !!! no questions about it !!! i mean even a honda gx 50 or a 79cc predy is far more powerful than the china girl, and more reliable to.
you want the best no fuss easy setup you will be impressed with ???
try out the dax titan 50cc motor with the rear mount chain drive kit
a clone 79 - 99cc predy motor frame mount with a small torque a verter from custommotoredbikes for even more power !!
the video is of the 99cc habor frieght bike that is an easy setup !!
here is a comlpeat 49cc q matic 4 banger with torque a verter setup
the q matic kt is 600$ but like i said its a night and day differance from the china girl
These kits are good http://www.zoombicycles.com/shop/
They are pretty good kits but they don't ship out of Canada
so they would be good for the OP.
I got 8 kits off them years ago before they got slapped for shipping to the US.
Yeah I got one about 5 years ago or so. Gave it to my daughter and she sold it to a friend. IT STILL RUNS GOOD. Rockout is in Canada so no problem there.
That's where I pick up my kits. No idea where the op lives, but there are other places in other parts of the country. I'm close enough to Zoombikes that I can drive over and pick up my order (about an hour with the Buick.. no good bike routes to get there from here ).
Here is a pic of the hole by the intake I was mentioning
That is a fairly common casting flaw that is only cosmetic.
The hole doesn't go through to the intake.
If you were more curious you would have removed the intake to
look in the intake tract to see if the hole went all the way through?
How many bent China girl cylinder fins have you straightened?
I have straightened fins with smooth jawed wide needle nose pliers
on well over 500 motors and continue to straighten a few on my
new motors which don't seem to have too many bent.
NEVER ever broken one!
They are thin and pliable and usually bend back really easily and
I never use heat.
If a get a tough one near the intake or exhaust or some webbing I
leave it bent.
I have noticed that a few old bushing motors had much thicker fins
and cleaner castings and there was some machining done on them in
various places that aren't done today.
The heads on the other hand are die cast and the fins if bent can not
be straightened and they will break off instead of bend most of the time.
I thought that brown stain was oil I'll take off the intake to look tomorrow since its to cold to ride now
Mea culpa, mea culpa, mea maxima culpa......... Alright I confess, - none! But I have straightened other aluminum parts from older vehicles & etc when I was younger.
In future I shall only offer advice on things with which I've had direct experience and not generalise. For my punishment I shall listen to Rap music all tomorrow to teach me not to do it again.
This one made me laugh................. most of us at some time or another have been guilty of given an uneducated opinion or two just based on what has worked or not worked on other projects in our past tinkering with whatever....
But I say please leave the rap "music" alone, you have done nothing to justify putting yourself through such horrid punishment as listening to that garbage that is some how mistakenly put in the "music" category, I always said they couldn't spell just the same as the rappers can't speak right and they forgot to put the letter C in front of rap.... because as a musician and someone who comes from a long line of musicians I can say for sure that rap is noise and trash talk and not music, rap was invented by lazy no talent people who couldn't cut it as a musician if they tried.
So there is my thank you for the good laugh and my unrequested opinion on rap crap....LOL!
Same here, they're really good.
My motor is not balanced at all though (not their fault though, its manufactured in china!), vibrates like crazy. That's my only real complaint.
They include a lot of extra parts which is nice including extra gaskets, and other things.
when I built my first bike I used a dax 47cc motor and out of the box I was impressed but I did not except much since I am 260lbs or more at any given time.
that said out of the box with a rt carb and voo doo exhaust the motor would pull me at over 30mph +. then I got a rse reed kit a puch 50cc hihi comp head and a rse reed kit.
I did a very mild port to the intake and exhaust more of a clean up. and a very mild 3rd transfer port and could easly run 40mph + with the stock 44t gear.
around 400 miles later the piston barren gave way so I got a dax balanced bottom end for 60 and his top end for 60 free shipping that way.
I cleaned up the ports put my hihi head on and voodoo exhaust along with minor port again.
the 66cc balanced had more low end and would run between 35 and 40 off the bat I sold it before it was completely broke in so I do not know what top speed was when it was broke in.
The guy that I sold the bike to was so happy because he had built several and none of his ran as smooth or had the power that this one had.
when I told him that all I really did was gasket match and clean the ports up he could not believe it.
I know I went on and on but all Im saying is it don't take much to get the right china girl to run the way it should and be more then what you need on a bike.
Agreed.......... ports cleaned up and a good carb tune with good e haust does way good for improved china girl......