So first of all- a 49cc motorcycle doesn't need a title or registration in the state of Idaho... so I've been riding around for the last couple days worry-free. Nice to know, and it means that Audrey can (and has) steal Cub from me to ride herself. Not that I blame her. It fits her, and she looks better on it than I do.
We left off with Cub running, but not able to idle in gear. I suspected a clutch issue (that was pretty obvious), so I dug out the clutch from Spare. I stripped and reassembled it, and learned a lot in the process. It's a centrifugal plate-type wet clutch, which is sort of the logical step between a simple chainsaw clutch and a traditional manually actuated motorcycle multi-plate wet clutch. The clutch housing is attached to a grooved heavy plate by means of screws and springs... well, here, look at this:
So the drive shaft basically comes in and spins the heavy plate and the clutch housing. A set of plates locked to the housing spin along with it. Sandwiched between those plates are a set of friction plates, which spin freely inside the housing but are locked to a central core. The core becomes the output gear, which sends power to the transmission. Between the first set of housing plates and the heavy plate are the rollers, which are really just little tube sections. They fit into angled grooves in the heavy plate- see them up there in the figure? So as the engine runs the heavy plate, clutch housing, and housing plates turn with it. The rollers stay in the deep part of their grooves, forced there by the angle of the grooves and the pressure of the springs. As the engine spins up, the rollers' inertia shoves them outward, into the point that the heavy plate grooves make with the first housing plate. That forces the housing plates and the center plates together, and friction causes them to spin together. That spins the core, which spins the output gear. It's a bit more complex than the simple centrifugal clutches you get on go karts and weed eaters, but it also provides a bit more finesse starting from a standstill.
I found that when I disassembled the spare clutch, there are stop screws which keep the springs a bit pre-loaded, and if those are removed the heavy plate basically just shoves the rollers into the friction plates and jams the clutch engaged. I assumed that this was the problem with the clutch on Cub, as well, so I was surprised to find the screws installed correctly. When I pulled the clutch off and broke it down, I found that someone else had gotten into the clutch at some point- but they'd put the rollers back in perpendicularly. They didn't fit into their grooves, which was actually what was forcing the clutch to stay engaged. I put them back in oriented correctly, and the next morning had a motorcycle that would start smoothly from a standstill. It's the little things in life, right?
That was my Saturday night. Yesterday I had to revive the battery, because it had become sulfated from sitting discharged, and it had discharged because the charging circuit wasn't hooked up. So today, I rode Cub to work (which was monumental on its own) and inserted a connector to tie the battery into the charging circuit. When I rode home and put a voltmeter on the battery, it was reading 6.3V- plenty of juice.
It's really exciting to have actually taken it somewhere for the purpose of providing transportation, rather than just on a test ride. And yet more exciting that the components are coming back online. Next goal is to get the headlight and taillight working (and the neutral light and speedo light as well). And mirrors. And side cover knobs. And... that whole list of things from the other day. Fun stuff.
-The Proprietor
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