Quick question about 66cc performance.

Dyetube

New Member
Oct 1, 2020
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Hey guys, quick question about sluggish performance...

As posted in my other thread, this is my first motorized bicycle build. I bought the 66cc motor with the CNC upgraded head from gasbike.net. I haven't yet gone through 2 gallons of fuel, but I am close. I followed what most people said and did a 16:1 oil to fuel ratio on these first two gallons to break the motor in. What is happening is, my bike has a VERY hard time taking off (even on a level, straight road), it really bogs down and would die if I didn't pedal. Even when I give it full throttle it bogs down (and if I held it full throttle it, again, it would probably die), and doesn't really go faster than 16 to 18 mph. I figure this is because of my fuel to oil ratio. I think the engine isn't getting enough compression because of the amount of oil in the gas, but wasn't sure. Am I correct on this?

Here's the build in case you need it:

1. Black Stallion ENGINE ONLY 66cc/80cc: https://www.gasbike.net/collections/engines-only/products/black-stallion-66cc-80cc-engine-only
2. NT Carburetor with CNC Velocity Stack # 1 - High Performance: https://www.gasbike.net/collections...or-with-cnc-velocity-stack-1-high-performance
3. Stock black muffler that came with my other engine: https://www.gasbike.net/collections/mufflers/products/chrome-exhaust-muffler-1
4. Stock CDI: https://www.gasbike.net/products/capacitor-discharge-ignition-cdi-coil

Fyi, this is (until I can buy another motorcycle), my daily rider. I'm looking for a balance between speed and daily reliability/durability. I've read that a 40:1 ratio gets you a high top end and that 20:1 is the balance between speed and daily riding. I'm trying not to invest too much into this project so I can save my money for a motorcycle but I'd like to be able to ride at or about as close to 30 MPH consistently as possible (if that is even possible). I've gotten the bike that fast a few weeks back after first building it, but not since. Any tips are greatly appreciated!
 

Greg58

Well-Known Member
May 1, 2011
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Newnan,Georgia U.S.A.
16/1 is too much oil, I run 24/1 to break in a new engine then switch to 32/1. Make sure the head gasket is not leaking, torque the nut to 12-14 foot pounds, use a torque wrench. If you are in a area where noise won't cause a problem try running without the muffler end cap, a lot of mufflers are very restrictive. If the muffler test helps you'll know an exhaust upgrade will help.
 

Dyetube

New Member
Oct 1, 2020
8
3
3
55
16/1 is too much oil, I run 24/1 to break in a new engine then switch to 32/1. Make sure the head gasket is not leaking, torque the nut to 12-14 foot pounds, use a torque wrench. If you are in a area where noise won't cause a problem try running without the muffler end cap, a lot of mufflers are very restrictive. If the muffler test helps you'll know an exhaust upgrade will help.
I'll try 32:1. I do think the head gasket might be leaking slightly. I'll check it tomorrow. I'm in a residential area but in the country(ish). I should be able to remove the muffle endcap no problem.