So, without going into a ton of detail, I have the itch for a new project to tinker with, but with being in classes to finish a degree and working on sorting out my finances and eliminating debt, I decided to build a motorized bicycle instead.
It has no practical application in my life really, just something to tinker with that is cheap. Who knows, maybe I will use it to go to work from time to time once I work out the bugs.
Funny enough, I have started backwards with my build and actually bought the engine first. What can I say, I'm weird. I even chose a questionable engine to use, known as the Phantom 85. Basically a factory built version of a YD100 with a Stihl MS460 cylinder and piston - well, chinese copies of them at least.
These engines are known to be quite powerful, and quite unreliable too. I told you I was weird.
They have fixed the biggest issue with the motors, which was their decision to use a loose fit graphite injected bronze wrist pin bushing. They would wear out extremely fast and cause the piston to turn and slap around in the cylinder and catch the rings on the ports and all sorts of other catastrophies.
The newest version they are selling now use a 12mm wrist pin and roller bearing. They achieved this by using the "110cc" connecting rod with the YD100 crankshaft and lower case.
The current issue is that the pistons are experiencing ring land and skirt failures. It may be a 1 in 100 type of issue, but it is still happening.
My plan for the motor is to in theory make it worse. How? Eliminate the reed valve and install an aftermarket piston with caber rings with no piston windows. I haven't decided yet on a domed 460 piston or milling down the top of a 380 piston to set a tighter squish gap. They are basically the same, but the wrist pin height on the 380 piston is 1mm lower. The squish gap on the Phantom motors is actually over 1mm, which is enormous. I will decide for sure once I can measure my own gap. The pistons are cheap enough anyway I may just order both to experiment.
What can I say, I am crazy.
My thinking behind this is due to the fact that this engine makes so much low down torque it has actually wrecked a couple of rod bearings on a couple of other bikes. That Low Speed High Load force on bearings is no joke.
Instead, I plan to clean up the transfers and intake port, widen the exhaust port (and possibly raise the port roof to add 2 degrees, but I will need to check timing). Also clean up the piston ports for the transfers and open them up a little. This is all advice from a person that builds competition chain saw engines. After talking with him for a bit, he said that he has never felt the need to window a piston on any engine he has built, and I take his word for it.
I also plan to split the cases so I can properly balance and true the crankshaft. Why not? Like I said, cheap tinker project. I like the idea of trying to take away just a bit of it's low down power in exchange for a higher top end and more RPM. Plus, I can always go back and window said piston later if I change my mind.
I am still deciding on what type of bike/frame to use for it. I am torn between spending the money on a high quality entry level gravel/hybrid bike OR one of the fuel tank frame Felt Fakers like the Zeda Dawn V2
https://www.bicycle-engines.com/zeda...as-frame-bike/
My big consideration is comfort. I am not actually trying to build a race bike. I want to have a sprocket set that can achieve maybe 30-35mph max and climb hills without much help from me. Some people have said the Felt Fakers can be made comfortable for taller riders, and I do like the style and built in fuel tank. The only thing I do not like is that it comes as a single speed. I may look into adding a 3 or 5 speed freewheel to the back.