questions regarding mods to china girl motorized bicycle

GoldenMotor.com
S

squirrel

New Member
Dec 2, 2010
60
0
0
hills of northern cali
first and formost let me start by saying i know the limits of these chinagirl kits. i seem to have been lucky in getting a "solid" one as ive not had a real problem with the motor...just carb, throttle, brakes...the usual.
anyways...im in the midst of a teardown/remodel of my current bike. i plan on selling it to fund my next build and wanted to tighten the whole "theme/look" of the bike. as an artist i have a very specific look in mind, the fit of the engine is rather tight so im not sure an aftermarket or replacement head will work...not that it matters, the bike runs 30+ on flat ground and thats fast enough for this frame.
my question...
can i use my dremel to modify the shape of the jug and head fins?
is the cast metal brittle?...i assume its steel?
i want more of a tube shape with a domed head.
will the engine cool properly with this mod?
thank you in advance
squirrel
 
B

bigbutterbean

Active Member
Jan 31, 2011
2,417
3
38
Lebanon, PA
Re: questions regarding mods to china girl

The entire body of the engine, as far as I know, is aluminum. It is somewhat brittle, but careful grinding with a dremel might not hurt it. I have been able to straighten out bent cooling fins with a flathead screwdriver, so it might not be terribly brittle. As far as cooling goes, slight modification of the fins shouldn't hurt anything. The head fins should be absolutely fine with a dremel, just dont do too much at one time or you may overheat the metal and take the temper out of it.
 
S

squirrel

New Member
Dec 2, 2010
60
0
0
hills of northern cali
Re: questions regarding mods to china girl

thanks guys! expect pics as im documenting the rebuild for an actual build log.
it will be titled: Ol Betsy becomes Sky Captain.
on a side note...steel piston sleeve?... havent had to take the engine apart yet...lol
 
J

JonnyR

New Member
May 13, 2012
1,203
1
0
37
ronkonkoma, new york
Re: questions regarding mods to china girl

most have a chrome liner not a steel sleeve and i wouldnt take to much off the head fins it provides alot of your cooling and you could end up warping it or overheating the engine
 
mew905

mew905

New Member
Sep 24, 2012
647
9
0
Moose Jaw
Re: questions regarding mods to china girl

I've used my dremel to "clean up" the jagged edges of the fins on my motor, never to actually cut into and shape them though. But I will warn you, the metal comes off really, REALLY easy, the amount of resistance (depending which bit you use) is similar to sticking a cool knife into a brick of unfrozen butter
 
P

PAracer

New Member
Sep 14, 2012
284
0
0
Steelton, PA
Re: questions regarding mods to china girl

Use a sanding drum if you're scared of removing too much material. A steel bit might sink in way to fast to control. Keep in mind that you will be removing the engine's only way of shedding heat.

Isn't there a Grubee engine model that has a round jug and head? I think it's a 48cc
 
Technocyclist

Technocyclist

Motorized Bicycle Senior Technologist
Jul 7, 2008
462
0
0
Asia
Re: questions regarding mods to china girl

I just use a flat file to smoothen the edges and remove the casting burrs, seems enough to do the work. :)
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Re: questions regarding mods to china girl

Rounding off the square corners won't hurt a thing unless you get carried away and take off way too much material. That shouldn't be a problem if you use common sense. To get that round look you'll only need to take off a small amount.
Typically you can remove as much as 10% of the surface area of a heat exchanger without seriously compromising its ability to remove heat. And the fins are a heat exchanger.

Tom
 
mew905

mew905

New Member
Sep 24, 2012
647
9
0
Moose Jaw
Re: questions regarding mods to china girl

It's a bit of a trade-off really with heat dissipation. Not enough material: it cant get enough heat out into the air, too much material, it'll retain the heat better. the key is to keep as much material as you can while increasing surface area. Better materials would help as well, but thats not an option for us. I still think a PC water cooling pump and radiator with copper tubing through the fins could work. I might give it a shot at some point.
 
Last edited:
You must log in or register to reply here.
Top Bottom