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1970 CL100 Cafe Project - Bore Information?

10460 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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hi, if you want to spent a few grand on the motor, it would do 90MPH. That's not going to happen.

If you think you can just fit a bigger piston and get big gains, easy, well you can't.

If you want to go faster, get a bigger bike.

Buy a manual, tune it and maintain it. Keep the motor stock. It will run like that until the end of time.

Danger, is my business."
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.
I doubt you will find rings or a stock +.25 piston. Don't strip it down before you have the right parts in you hand, or absolutely know that they are available. Plenty of pistons are available for the 125cc version of this motor, but not the 100cc version. CB/CL/SL/XL 100cc parts are a hassle.

A bigger piston on this bike will give you jack more horsepower. Forget buying some wonder piston kit off ebay from China to fit your bike: I'm 80% sure it will be crap quality.

The best compromise is to keep the bike 100% stock.

This " baby sized vintage " would haul a fat man from coast to coast and back.

Danger, is my business."
You can use a 125 piston but I think the pins are slightly different.
If only the 125cc piston wasn't the wrong size, the wrong piston crown shape, the wrong compression ratio, and wrong piston pin size.

Need I go on?


There is no way in hell of reaming a CL100 rod to oversize, like zero, zippo or ziltch.

Danger, is my business."
Give me $3.5K = 90MPH+




Danger, is my business."
Buy a Skyteam ACE 125 tank and seat.

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I think the only thing you will learn is bikes cost real money, and hotting up a bike is beyond you meagre skills.

Danger, is my business."
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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.
Well you don't need a long flat brat seat on a bike that puts out about 9 BHP.

Unless you plan on having a relationship with a blow up woman... Who you gonna haul?

Danger, is my business."
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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.
The 125 motor fits straight in.

Danger, is my business."
Any other useful technical suggestions?
CC's sonny.

Danger, is my business.
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