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  1. #1
    CB750 New Member HoneyBadger's Avatar
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    Question Max speed not going above 110km/h

    Hi guys,

    Recently I've bought a CB750C from 1983 but I'm a bit disappointed that I only get him to max 110-120km/h in 5th gear at 9000rpm.
    As I read here on the forum and on the internet that he should go a lot faster, the motorbike has been modified and rebuilt by an unknown person.
    Can somebody help me out and or tell me if this is a mechanical issue or something else?

    engine s/n : RC01E-2244114

  2. #2
    CB750 Guru amc49's Avatar
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    The clutch has to be slipping to go that slow at that rpm. Even 4th gear should go faster than that.

  3. #3
    Moderator dirtdigger's Avatar
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    Have you checked the sprocket sizes see if it has been changed??

  4. #4
    CB750 Guru amc49's Avatar
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    I went there mentally but once I had 17/49 instead of OEM 18/46 and still could go 105 easily and mph not kph. To go as slow as he is the sprockets would have to be comically changed, the rear would be huge, that 49 was. On 530 chain. I ran 18/42 (1100 gearing) for years and the theoretical would have been like 135 mph. It was only barely 5500 rpm at 75-80+ mph in 5th. About the rpm a DOHC powerband begins to howl a good header as cams come into phase.

  5. #5
    CB750 New Member HoneyBadger's Avatar
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    Checked the sprocket sizes and they have the original amount of teeth as it should. Is there a possibility that the gears in the gearbox itself could have been changed altho i dont see the plus in doing such a thing.

  6. #6
    CB750 New Member HoneyBadger's Avatar
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    Also been thinking about that, are there any other parameters where i can see that the clutch would be slipping before opening that compartment. The oil was clean and there is not excessive heat at where the clutch is, which i would think there would be if it was slipping or am i wrong?

  7. #7
    CB750 Guru amc49's Avatar
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    You just have to be familiar with engine slipping to know clutch, there is no other way to tell it. The rpm is simply way high for your speed. There are flat NO other gears that will fit in trans to alter that. DOHC clutches tend to slip pretty easy anyway if hotrodded, I changed my first one on a bike at 4000 miles. They are not durable at all if ridden hard.

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