China girl 66... Maximum RPM?

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buzbikebklyn1

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Hey guys... I had a customer today ask me what the maximum safe RPM for a China girl that's been broken in and is in good shape?
I had no definite answer for him!
I set up my bikes for low end torque not high RPM power, so I never spin mine much past 5,000.
Consequently the engine lasts longer... I know they are capable of higher RPM but why stress the engine?
Who's got the correct rev limits?
BBB
 
hi

according to z-box

specs of 66cc

1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 66cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.7kW @ 5500rpm
6. Economy: 100 km/1.5 litre fuel
7. Nominal speed : 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9.5kg
10. Bore: 47mm
11. Stroke: 38mm
12. Compression ratio: 6:1

specs of 48 cc


1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 48cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.2kW @ 5500rpm
6. Economy: 100 km/1.2 litre fuel
7. Nominal speed: 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9kg
10. Bore: 40mm
11. Stroke: 38mm
12. Compression ratio: 6:1

:whistle:

1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 48cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.2kW @ 5500rpm
6. Economy: 100 km/1.2 litre fuel
7. Nominal speed: 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9kg
10. Bore: 40mm
11. Stroke: 38mm
12. Compression ratio: 6:1

ohhh my 48cc even tho its a rse hp1.5
topped out at 65 khp with a 44 rear an modded stock exhaust .
revs felt like 7000 rpm

now about to add sbp shiftkit.expansion.lo profile air ,metal throttle body ,rocker kill .

brad
syd
 
So...5500 seems to be the manufacturers limit... good.
I wasn't far off, better to err on the side of safety with these little hand grenades.
Thanks.
BBB
 
hi

according to z-box

specs of 66cc

1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 66cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.7kW @ 5500rpm
6. Economy: 100 km/1.5 litre fuel
7. Nominal speed : 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9.5kg
10. Bore: 47mm
11. Stroke: 38mm
12. Compression ratio: 6:1

specs of 48 cc


1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 48cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.2kW @ 5500rpm
6. Economy: 100 km/1.2 litre fuel
7. Nominal speed: 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9kg
10. Bore: 40mm
11. Stroke: 38mm
12. Compression ratio: 6:1

:whistle:

1. Engine Type: Single cylinder, air-cooled, 2-stroke
2. Type of fuel mix :(16:1/20:1)
3. Displacement: 48cc
4. Ignition: C.D.I. ignition
5. MAX.Power: 1.2kW @ 5500rpm
6. Economy: 100 km/1.2 litre fuel
7. Nominal speed: 30-35km/h
8. Fuel tank: 2 litre
9. Overall weight: 9kg
10. Bore: 40mm
11. Stroke: 38mm
12. Compression ratio: 6:1

ohhh my 48cc even tho its a rse hp1.5
topped out at 65 khp with a 44 rear an modded stock exhaust .
revs felt like 7000 rpm

now about to add sbp shiftkit.expansion.lo profile air ,metal throttle body ,rocker kill .

brad
syd

The shift kits worth every penny, just down load the assembly manual to a lap top and pay close attention as you put it together.
Most of the holes in the mounting plate, U bolt clamps, and were the engine its self bolts to the mount will need to be elongated and filed out... just work slowly, measure carefully before drilling.

Chain alignment and tension are crucial to the smooth operation of a shift kit.

Once you have the engine were you want it make sure your carb and air cleaner and exhaust/exp. pipe all fit well BEFORE drilling and filing!

I use several different straight edges and rulers for chain alignment, the straighter the chains run the less drag and wear there will be on the system, it will shift easier as well with less inner chain ring jumps.
Don't forget the jump stop! its very important to save your frame in the event of a major drive chain failure.
Good luck, thanks for the RPM 411
BBB
 
yeah. 5500. the porting durations/areas restrict it to 7k. so you may get that, but at the cost of reliability...(with these? what?! :p )

tweaking can alter this, but after getting 80km/h from one, then experiencing an....isssue, im just concerned with power/torque. lugging power. :)

speeds great. until you stop suddenly :giggle:
 
Everyone that runs a China girl needs to remember, these things are cast from Chinese beer cans... what can we really expect out of them?
Look at the Morini... its cast from Italian beer cans, it got less displacement yet puts out 3 times the power with way better longevity...
Now what we REALLY need is a china doll clone that cast from good old AMERICAN BEER CANS!
LOOK OUT...
lol
BBB
 
yeah. i would love to be able to buy an american made engine. although im sure the price would be much higher. but i think if the price truely reflected the quality. i would have a problem paying more. it just seems that never the case these days.
 
Everyone that runs a China girl needs to remember, these things are cast from Chinese beer cans... what can we really expect out of them?
Look at the Morini... its cast from Italian beer cans, it got less displacement yet puts out 3 times the power with way better longevity...
Now what we REALLY need is a china doll clone that cast from good old AMERICAN BEER CANS!
LOOK OUT...
lol
BBB

are you really serious that they are built from beer cans? If so i'm building my own from Australian beer cans. LOL
 
When I calculated the top speed and gearing of my bike I think at wide oped throttle the engine would hit about 7500 RPM. I don't normally go that fast though. Doesn't sound healthy at all.
 
These engines let you know when they reach max RPM through sound and feel. There is a point where the engine goes from smooth and happy to vibration and strain. To me, that is a better indication than a tachometer.
 
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