What's your most desirable accessory for a China Girl Motorized Bicycle?

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GearNut

Active Member
Aug 19, 2009
5,104
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38
San Diego, Kaliforgnia
Re: What's your most desirable accessory for a China Girl?

High quality bearings throughout.
Everything else becomes useless when the wrist pin bearing grenades or a crank bearing galls up.
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
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Dallas
Re: What's your most desirable accessory for a China Girl?

High quality bearings throughout.
Everything else becomes useless when the wrist pin bearing grenades or a crank bearing galls up.
I have to agree with you. The Chinese bearings are crap. I notice the new Flying Horse motors advertise they come with Japanese bearings.
 

wayne z

Active Member
Dec 5, 2010
1,743
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louisiana
Re: What's your most desirable accessory for a China Girl?

High quality bearings and a balanced crank would make these into a pretty good motor.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

I agree 100% on the bearings and a better balanced crank assembly.

I never had one of these engines back when they had the bronze bushing for the upper bearing instead of the caged needle bearing like they do now, but it seems I have read where people had said the engines with the bushings were better balanced, if that is true it seems that maybe removing some material from the cranks counter weights opposite the rod journal might help the balance since the piston/pin area is lighter now than it was with the bushing.....Shrug?
 

thegnu

New Member
Sep 15, 2011
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freedom pa
Re: What's your most desirable accessory for a China Girl?

My shift kit , disc brakes ,custom fuel tank in that order , lol so actually the motor accessories are last .
 

biknut

Well-Known Member
Sep 28, 2010
6,631
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Dallas
Re: What's your most desirable accessory for a China Girl?

I agree 100% on the bearings and a better balanced crank assembly.

I never had one of these engines back when they had the bronze bushing for the upper bearing instead of the caged needle bearing like they do now, but it seems I have read where people had said the engines with the bushings were better balanced, if that is true it seems that maybe removing some material from the cranks counter weights opposite the rod journal might help the balance since the piston/pin area is lighter now than it was with the bushing.....Shrug?
All the cranks I've checked needed heavier weight on the counter weight side.

 

biknut

Well-Known Member
Sep 28, 2010
6,631
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Dallas
Re: What's your most desirable accessory for a China Girl?

My first HT was a bushing engine back in '06. It was by far the worst engine I had. Very unbalanced, and it grenaded when I tried to hit 30.
Sounds a lot like my X80 motor.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

Thats good to know, I was just guessing based on something I remember reading on here a long time ago, but then again I may have it mixed up and maybe whoever it was said what you did about needing more weight on the counter weight side.


All the cranks I've checked needed heavier weight on the counter weight side.

 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

Well, I,ve never had a bushing engine so I have no experience with them, I remember some debate in the past about them and in the midst of one of the debates is where I thought I remembered someone mentioning the '' better balance '' thing, may be hog wash as you sorta said here, I'm glad we have the needle bearing instead on the bushing.

Peace, Map


My first HT was a bushing engine back in '06. It was by far the worst engine I had. Very unbalanced, and it grenaded when I tried to hit 30.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

Biknut, how did you figure out the counter weight side was too light?

Do you have a homemade contraption to roughly balance the crank assembly?

Map
 

moonerdizzle

New Member
Jun 28, 2009
874
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Cheese head capitol
Re: What's your most desirable accessory for a China Girl?

I prefer bushings for one reason. Most bushings slowly fail and let you know "hey! I'm old and wore out . Replace me before I ruin your day."
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

Yeah I kinda figured the worn bushing would start knocking on the top end before it completely failed which would be a fair warning that it needed to be replaced.

But like I said I have no experience with bushings in these engines so I can't swear to anything concerning how they are/were, I figured they got away from them because they had a very short life in these engines and were causing loads of failures

Map


I prefer bushings for one reason. Most bushings slowly fail and let you know "hey! I'm old and wore out . Replace me before I ruin your day."
 

Texhun

New Member
Aug 2, 2011
322
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Rosebud Texas
Re: What's your most desirable accessory for a China Girl?

I lost my first two HT's because of those dumb needle bearings on the wrist pin. On my current engine I replaced the wrist-pin needle bearing with a bushing. Mapbike this is by far the best engine I've had! It's smoother and better balanced, this might sound a little off but it's also got way more power too! I run this engine way harder than the first two and it's gone twice the distance of the first two engines combined. I'm all for bushings in these engines. I wanna try doing a crank job on it sometime, seems like it just might be worth it. Just for the guys wondering, it's the K-80 from BGF, the first two were PK-80's also from BGF. Ironic isn't it? rotfl
 
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mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Re: What's your most desirable accessory for a China Girl?

Texhun

Did you machine the bushing yourself?

Or did you find a source for them?

Peace, Map


I lost my first two HT's because of those dumb needle bearings on the wrist pin. On my current engine I replaced the wrist-pin needle bearing with a bushing. Mapbike this is by far the best engine I've had! It's smoother and better balanced, this might sound a little off but it's also got way more power too! I run this engine way harder than the first two and it's gone twice the distance of the first two engines combined. I'm all for bushings in these engines. I wanna try doing a crank job on it sometime, seems like it just might be worth it. Just for the guys wondering, it's the K-80 from BGF. Ironic isn't it? rotfl