1970 CL100 Cafe Project - Bore Information?
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1970 CL100 Cafe Project - Bore Information?

This is a discussion on 1970 CL100 Cafe Project - Bore Information? within the Technical forums, part of the Caferacer.net Forums category; 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 ...

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Thread: 1970 CL100 Cafe Project - Bore Information?

  1. #1
    Junior Member CNorthness's Avatar
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    1970 CL100 Cafe Project - Bore Information?

    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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  2. #2
    Banned Witworth's Avatar
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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."

  3. #3
    Senior Member hillsy's Avatar
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    Standard CL100 bore is 52mm and CB750 bore is 61mm. That's a massive bore increase for such a small engine. Then you've got the wrong size gudgeon to deal with....

    Have to agree with ol' witto - you need a bigger bike.

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  5. #4
    Senior Member hillsy's Avatar
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    And BTW - that bike has only had 2 owners since 1973? Respect it as a survivor and keep it original.

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    Junior Member CNorthness's Avatar
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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.

  7. #6
    Junior Member CNorthness's Avatar
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    Crazy, right? Including me, three since it was new, two since 1973.

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    Banned Witworth's Avatar
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    Quote Originally Posted by CNorthness View Post
    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."

  9. #8
    Senior Member hillsy's Avatar
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    Here you go - here's a thread with Jag in it:

    http://forums.sohc4.net/index.php?topic=78564.0

  10. #9
    Senior Member knappyfeet's Avatar
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    Ding.........another bike gets its wings.

    Powroll has kits for the 100 but you need some machining. You can use a 125 piston but I think the pins are slightly different.

    I heard of folks doing the 750 piston work but what a machining and tuning nightmare. Stroking it out, compression issues.......just a lot of poop...for what.......18 hp.

    But Wits correct.........you never get what you want out of this 100. Since your probably going to cut up the frame make a straight 125 by sourcing a motor or maybe a 175.

    You have a good history being the 3rd owner of this classic honda..... but it would be a shame to cut it up to a cafe only to get a r top speed of 75mph....maybe.

  11. #10
    Banned Witworth's Avatar
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    Quote Originally Posted by knappyfeet View Post
    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?

    Yep:

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

    Danger, is my business."
    Last edited by Witworth; 02-26-2015 at 10:55 PM.

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