Hey thanks Chaz.
Crassius I'm intrigued, what do you mean about the piston?
it's my original zoom motor, which I believe is a pk80. I know your familiar because I remember reading that you thought they vibed at low rpm, but the A80 didn't and you prefered the a80. I am actually considering buying another engine from zoom. On their website it says and shows it completely disassembled. so I could clean up all the ports and transfers, and then assemble with better hardware. but mine does have a patch of vibes that are pretty intense in the mid-range.
Are you saying that is a characteristic of the pk80?
becuse I would have to rethink buying another because I would only buy another engine in hopes of not having a patch of wicked vibes anytime. other than that patch o vibes I love this engine.
However, I have "journey" developments. The back wheel is warped, so I have ordered a replacement from husky. and I decided I want jackshaft kit to go with my coming 3 spd internal hub. I understand that I will have to watch my throttle application as I change gears up and down. As I was checking out the bike closely I found a frame crack, again. So I stripped her down, and pulled out my other electra townie frame. when I wanted to use this frame before I couldn't because the engine chain just couldn't fit past the frame on the left side. but now with a jackshaft already in the scheme, she is back in play.
and I'm kinda happy about it. this is the 3rd crack in the other frame. in the picture below, the frame has orange lines where the first 2 cracks were, and the yellow is the new crack, so shes 3 strikes. although bad mount tightness maintenance is the fault of the first one by the seat stem.
the new frame has a couple benefits in the added strong points with the blue arrows. the seat tube is a little smaller, but I ordered the jackshaft after knowing I'm changing frames. I will still need my front mount modded, but thats fine. the other small bonus of the frame change it that this frame has a coaster brake, so it does not have v brake mount as does the cracked one. my new rear wheel is a drum brake as well, so I dont need or want the v brake mounts. new frame doesn't have through frame cable paths, but I don't care about that.
so that all being said, I'm thinking of a new engine because of the 3 cracks. and if all pk80s are suspect of intense mid range vibes...