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1970 CL100 Cafe Project - Bore Information?

10461 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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you're going to bore it to solve compression problems that you say may or may not exist? also when your first post stated that everything seemed straightforward except the engine??? nope... nope nope... don't put a wrench to that engine, you'll ruin it with that mindset.

put everything back together and learn to maintain the bike, or you'll be selling the whole garage full of boxes of bike in a few years.
how many projects do we see where someone who's never been into an engine before decides they have what it takes to go frankensteining the thing??? the kid probably doesn't even own a dial caliper, let alone what it's going to take to do this surgery... argh... another one bites the dust
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