bought a china doll from ebay

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feelyx

New Member
Jun 30, 2012
140
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sac. ca 95821
So I bought a CG for my wife's bike, and after reading the horror stories, I decided to disassemble completely. After checking the crank...:-||
I found one side weighing 803 grams and the and the other side at 881 grams.
After a bit of machine matching sizes on the weights and crank I now have 2 side weighing 586 ea. with 0 run out all the way to the end of the shaft, I decided to lighten the crank up alittle from 1684g to 1172g. dnut
Next up is drilling the journal holes bigger to put in offset spacers in to increase the stroke up to 2mm. I may make a billet rod, if this one isn't straight.
Another thing I found was the piston was too tight in the bore, so a little adjustment to the skirt will be necessary when I cut the top to match the head chamber.
The clutch pads.... well I will work on that. Most likely a bronze product would be best.
 

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feelyx

New Member
Jun 30, 2012
140
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sac. ca 95821
Crank is done.... woo woo!
I ordered some high quality bearings should be here in a day or 2.
http://www.vxb.com/page/bearings/PROD/Kit9703

My wife reminded me this is for her bike and she doesn't need a stroked, bored or sup'd up engine.. .crt.
So if I find a used engine, I will stroke that one.... and go for the big 5mm and mill a spacer for the bottom of the cylinder. Also I think I could remove 200g more off the crank without any problems.

On to the clutch.....laff
 

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maurtis

New Member
Dec 14, 2011
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Kyle, TX
Those are the kinds of cajones, skills, and tools I wish I had when it comes to motors! Great work, I cannot wait to see how it turns out when you get the bike on the road.

I am a big chicken when it comes to anything under the head, lol.
 

feelyx

New Member
Jun 30, 2012
140
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sac. ca 95821
Its as balanced as a single cylinder will ever be... both sides are cut equal in size and weight. The weights have metal removed to match journal weight. Of course 0 run out on the shafts. Runs like a champ at 3k on my lathe.
 
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feelyx

New Member
Jun 30, 2012
140
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sac. ca 95821
I have my clutch trued and running straight.... For a while there I was thinking there will be no metal left tryin' to get it to run straight to the shaft.
all surfaces are flat to each other.
I am changing the bearing balls for the "flywheel". I don't see those 3mm steel balls lasting in that enviornment, So I ordered some ceramic ones that can run with very little lube, since it just all flicks off into the clutch disc anyways.
http://www.vxb.com/page/bearings/PROD/Loose-Ceramic-Balls/Kit11914
For the friction material....I was going to go with med clutch/brake but have decided to look for some porous bronze 1/8" thick sheets and cut real discs for each side and bond them on, instead of these little squares or circles.
 

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multipaul

New Member
Mar 31, 2012
74
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0
Germany
Hallo feelyx!

Thank you for the interesting pictures and this great report.
There seems to be nothing what you accept as a given. That's fine and the lathe is very helpful.

You know that a lightened crankshaft gives you a better accelaration. No better top speed and a less pulling on little mountains. I don't know your area and whether there are many traffic lights or mountains. The flywheels are nothing more than a kind of energy storage. And they are good for a constant idle at low revs. Nevertheless it's interesting.

Your piston was too tight in the bore from factory. My piston was from factory 0.1mm smaller than the cylinder. 0.03 or 0.04 would have been enough in my opinion. Did you measure the play or did you make the so called "fall test"?

The connecting rod in your crankshaft seems to be rather short. It looks as if you had already enlarged the stroke.

Either way, thank you for your nice review so far.

Multipaul
 

feelyx

New Member
Jun 30, 2012
140
1
0
sac. ca 95821
Hallo feelyx!

Thank you for the interesting pictures and this great report.
There seems to be nothing what you accept as a given. That's fine and the lathe is very helpful.

You know that a lightened crankshaft gives you a better accelaration. No better top speed and a less pulling on little mountains. I don't know your area and whether there are many traffic lights or mountains. The flywheels are nothing more than a kind of energy storage. And they are good for a constant idle at low revs. Nevertheless it's interesting.

Your piston was too tight in the bore from factory. My piston was from factory 0.1mm smaller than the cylinder. 0.03 or 0.04 would have been enough in my opinion. Did you measure the play or did you make the so called "fall test"?

The connecting rod in your crankshaft seems to be rather short. It looks as if you had already enlarged the stroke.

Either way, thank you for your nice review so far.

Multipaul
Hi Multipaul,

Thanks for the kind comments.

Yes, I understand the properties of kenetic energy. There is also a point where it also becomes a waste and the flywheel won't excellerate beyond a certain rpm.

I left plenty of weight on the crankshaft and "flywheel" to manage take offs and hills. Like I said earlier, I could take 200g more off without any problems. Plus, the bike has a shifter kit which has plenty of low gears.

With the rings off the piston, the piston would not fall through the bore, in fact it took significant force to push through. After measuring the bore and the piston, the piston is bigger at the base of the skirt then the ring landings.
So I will have to take some off there.

No enlarged stroke yet, that will be on the next engine, where I will go "all out"
.wee.

feelyx
 

multipaul

New Member
Mar 31, 2012
74
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0
Germany
Hi Feelyx,

you know what you do. I'm sure about that.
So I'm curious to see how it goes on with this engine and how your results are.

Toi toi (= good luck) - Multipaul
 

feelyx

New Member
Jun 30, 2012
140
1
0
sac. ca 95821
After aligning the engine case and checking the alignment to the crank, I found the deck height off. So I will have to remove the studs and flycut, I am going to take .25mm off. I will add 2 alignment pins, but want to confirm all my measurements when the japanese bearings arrive to be absolutely positive its perfect.

I actually want to raise the cylinder so the piston completely clears the intake port. So an extra thick aluminium base gasket will need to be laser cut out when I get that far.

Also a side note... to make a true 80cc, I will have to increase the stroke to 47mm from the 39mm it is now. So, an 8mm spacer under the cylinder will be needed for the increased stroke, and I am sure the piston will have to be cut to clear the crank. So if anyone has a seized engine they would like to get rid of please contact me. As I want to build a screamer.
brnot xct2 .wee. dnut
 

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feelyx

New Member
Jun 30, 2012
140
1
0
sac. ca 95821
Here is the skelaton of the clutch... The pad material and bearings should be here tomorrow for some assembly. I figure 5 big pads will be better than the 15 smaller ones that came stock.

If your clutch is slipping check the pads, as the design of this clutch, the pads need to free float. I found mine where hammered in tight and some where not touching the back friction disc.


dnut
 

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