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1970 CL100 Cafe Project - Bore Information?

10462 Views 31 Replies 10 Participants Last post by  monkey
Yo! Sorry if this is a subject that's been covered already. I'm new to the forum and couldn't seem to find anything. So! I bought a 1970 CL100 back in July from the second owner, who bought it back in 1973. He used it sparingly, but maintained it well until about five years ago,. It has sat since then. I stripped the bike to a motor and a frame, and all seems straight forward thus far except for the motor. Given the scooter-esque displacement, I'd like to add a little more get up and go, while simultaneously getting rid of any compression problems that may or may not be present. So, hey! Let's just bore it, right? BUT... I have no idea what the best compromise between sustained reliability and performance may be... I've heard of people boring the cylinder to fit a 750 sleeve and piston, and that it's extremely reliable, the only difference being that the 750 piston requires a 15mm wrist pin rather than the 14mm in the 100. That can be reamed, correct?

But is that even the best option? What would be the displacement, horsepower, and performance gains on this? Would anyone happen to have firsthand experience with doing such a modification on this bike? Any and all performance/reliability tips would also be greatly appreciated.
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I understand this is basically a scooter. I'm not trying to make it anything else. Buhhhhht If I'm going to take it all apart to hone it and replace the ring then I might as well add some displacement. I'm just asking for the best compromise, not a magical rocket from this baby sized vintage.
Crazy, right? Including me, three since it was new, two since 1973.
Hmmm... Interesting. Thanks for the links and such.

But! It's decided. It's getting cafe'd! It's been a dream for far too long to keep stock. Hmmm... Interesting indeed. Sure, It's not a racer. But a cafe- commuter is appealing to me. Just for a first time full build, you know?

I understand that I'm inexperienced in this sort of work. But my main interest is learning. I've been in and out of cars my whole life, so I figured I'd try my hand at some motorcycle science. Thanks for those of you that understand that it can be done. That's my goal. I understand that it's hard, weird, and generally dumb work, but being that it CAN be done, I'm just looking for info. Thank you for the links and such. Any more support would be greatly appreciated.
That's exactly the point. I won't learn unless I try this sort of thing. I bought the bike for next to nothing and have plenty of room to lose out. I'm paying for the learning experience. Whatever time and money I throw at this will be for learning's sake. Thank you for all the technical support. I believe a 125 from the same era uses the same mounts and all, correct? Just as an afterthought for an option B, given I muck this up horribly.
But! As far as style, I don't know if this is cafe sacrilege, but I plan on fabricating a hoop for the rear of the bike and welding it on to replace the forked back end, then building myself a long, flat brat seat.
Thanks, Jaguar. Likely the best post on the thread thus far. Over the last few days I think I've come to the same conclusion. I'm going to inspect the cylinder walls for any damage, and if all is well, put it back together and build something to swap. Yes, everyone: Build another gutless motor to make less-slow (very well said, Jaguar). Again, money can buy a racer or a buildable platform. But this is all for knowledge.

Brat seat because I think they look bad ass.

I'm not raking any forks or trying to find any chrome, chainlink ape hangers; So nah. Not choppers.

But! I'm fond of the hot motor described by kerosene. Any other useful technical suggestions?
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