I’ve been looking into buying a 66cc bicycle engine kit off of Ebay from Boy Go Fast and I can’t decide weither to go for it or not. I got a few specs from the seller:
Model : Z2-80
Power * Rotary Speed
Rated Power : (2.5HP/5000r/min)
Max. Power : (5-6HP/6000r/min)
Ignition Mode : CDI
Compression Ratio :6 : 01
Driving Ratio :18 : 01
Fuel type : No. 90
Mixing Ratio for Fuel and Oil: 16:1 for break period (first 300 miles) 25-30:1 after
Fuel Consumption :120-170 MPG
Clutch Type : Friction Plate / Dry
Speed Limitation :25-40MPH
10T front sprocket
44T rear sprocket
#415/#50 Chain
It says speeds up to 40MPH, but with 18:1 drive at 5000rpms and 24 inch wheels that’s only 20MPH, and at 6000rpms that’s only 24MPH. I’m not missing something am I? 10T front sprocket and 44T rear, that’s a 4.4:1 ratio, so the engine must be geared down to at least 4.09:1 if it’s a final drive ratio of 18:1. I’d like to have speeds of at least 50MPH. I’m 155 pounds, and if I recall my bike is only around 20 some pounds.
I’d prefer peak power to be around 5000rpms at 50MPH.
Some of the mods I was planning I doing were raising the compression ratio (CR) to 9:1. I have access to 100LL avgas in my area if I had to mix some with regular gas.
I’d use a NGK B6HS spark plug and either stick with the stock spark plug wires or make some solid-copper core wires out of some RG6 quad-shielded coax. I’d like to advance the timing for the increase CR but I don’t know how to do that on these little engines.
I’d install a reed valve, I can’t find any reasonably priced ones for a 66cc, would a 49cc reed valve (click here) work on a 66cc engine if I made an adapter?
I’d either purchase a expansion chamber or attempt to make my own using one of the online calculators.
As for the intake, I was using this calculator to try to find the optimum length at 5000rpms. However this calculator is for a 4-stroke engine, would I have to divide the results by 2 to get a accurate number or is it a completely different formula for two strokes? And I'd most likely use a Amsoil CrankCase Breather Filter (the blue ones), high flow and one of the best filtering filters on the market.
Finally a few aeromods made with coroplast and inspired by the AeroCivic .
Model : Z2-80
Power * Rotary Speed
Rated Power : (2.5HP/5000r/min)
Max. Power : (5-6HP/6000r/min)
Ignition Mode : CDI
Compression Ratio :6 : 01
Driving Ratio :18 : 01
Fuel type : No. 90
Mixing Ratio for Fuel and Oil: 16:1 for break period (first 300 miles) 25-30:1 after
Fuel Consumption :120-170 MPG
Clutch Type : Friction Plate / Dry
Speed Limitation :25-40MPH
10T front sprocket
44T rear sprocket
#415/#50 Chain
It says speeds up to 40MPH, but with 18:1 drive at 5000rpms and 24 inch wheels that’s only 20MPH, and at 6000rpms that’s only 24MPH. I’m not missing something am I? 10T front sprocket and 44T rear, that’s a 4.4:1 ratio, so the engine must be geared down to at least 4.09:1 if it’s a final drive ratio of 18:1. I’d like to have speeds of at least 50MPH. I’m 155 pounds, and if I recall my bike is only around 20 some pounds.
I’d prefer peak power to be around 5000rpms at 50MPH.
Some of the mods I was planning I doing were raising the compression ratio (CR) to 9:1. I have access to 100LL avgas in my area if I had to mix some with regular gas.
I’d use a NGK B6HS spark plug and either stick with the stock spark plug wires or make some solid-copper core wires out of some RG6 quad-shielded coax. I’d like to advance the timing for the increase CR but I don’t know how to do that on these little engines.
I’d install a reed valve, I can’t find any reasonably priced ones for a 66cc, would a 49cc reed valve (click here) work on a 66cc engine if I made an adapter?
I’d either purchase a expansion chamber or attempt to make my own using one of the online calculators.
As for the intake, I was using this calculator to try to find the optimum length at 5000rpms. However this calculator is for a 4-stroke engine, would I have to divide the results by 2 to get a accurate number or is it a completely different formula for two strokes? And I'd most likely use a Amsoil CrankCase Breather Filter (the blue ones), high flow and one of the best filtering filters on the market.
Finally a few aeromods made with coroplast and inspired by the AeroCivic .
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