Hey everyone, I'm looking to get another opinion on the issue my motorized bike is having. This is a chinese 80/66 cc "flying horse" engine and is my first build. It didn't take me too long to get it up and running, and for the first few months (despite some minor troubles to work out) it steadily ran smoother and faster over time as it should. I got probably at least 100 miles on it.
However, recently after tightening down several components I observed a considerable loss of power, and behavior that I identified as 4 stroking after doing a little research. I tinkered and experimented with it and thought I nailed the problem down to be either the CDI or the carburator, so I ordered replacements for both, a stock CDI and a "high performance" carb. When the parts arrived the CDI wouldn't spark, so I left the same original CDI (which produces what looks to me like a nice spark) on the bike and tried out the new carb. A replacement CDI is in the mail. The bike still 4 strokes heavily while riding. It hardly goes faster than 12 mph on the road I'd say, and the motor produces a very improper sound in relation to the throttle position.
When idling however, the engine sounds great though. Proper 2-stroke noise and pretty good throttle response. Even when I lift the back wheel and let go of the clutch, the engine runs greats and spins the back wheel mighty fast. Very little/no four stroking with the exception of some occasional problems at WOT. So the engine really only has problems under load/under the weight of a 140 pound person.
My gas is mixed 32:1 maybe closer to 34:1. I broke it in with 20:1 There's a little bit of smoking, but nothing excessive. I worry that the wires coming out of the engine (from the magneto, right?) are pretty close to the hot muffler, and may have even touched at some points in this bike's career. Also one of the mounting studs for the muffler is pretty loose (spins easily), but I don't think this is a problem? I don't believe the loss of power is compression related, because the bike provides a lot of resistence before it starts right up.
What do you all think the issue might be? Let me know what other information I should add.
Thanks!
However, recently after tightening down several components I observed a considerable loss of power, and behavior that I identified as 4 stroking after doing a little research. I tinkered and experimented with it and thought I nailed the problem down to be either the CDI or the carburator, so I ordered replacements for both, a stock CDI and a "high performance" carb. When the parts arrived the CDI wouldn't spark, so I left the same original CDI (which produces what looks to me like a nice spark) on the bike and tried out the new carb. A replacement CDI is in the mail. The bike still 4 strokes heavily while riding. It hardly goes faster than 12 mph on the road I'd say, and the motor produces a very improper sound in relation to the throttle position.
When idling however, the engine sounds great though. Proper 2-stroke noise and pretty good throttle response. Even when I lift the back wheel and let go of the clutch, the engine runs greats and spins the back wheel mighty fast. Very little/no four stroking with the exception of some occasional problems at WOT. So the engine really only has problems under load/under the weight of a 140 pound person.
My gas is mixed 32:1 maybe closer to 34:1. I broke it in with 20:1 There's a little bit of smoking, but nothing excessive. I worry that the wires coming out of the engine (from the magneto, right?) are pretty close to the hot muffler, and may have even touched at some points in this bike's career. Also one of the mounting studs for the muffler is pretty loose (spins easily), but I don't think this is a problem? I don't believe the loss of power is compression related, because the bike provides a lot of resistence before it starts right up.
What do you all think the issue might be? Let me know what other information I should add.
Thanks!