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Top speed/ power band CB750 question

This is a discussion on Top speed/ power band CB750 question within the General forums, part of the Caferacer.net Forums category; K0 had a redline to 8500rpm K1-K6 had a redline at 8000 rpm F/F1 had a redline at 8500 rpm K7/K8 had a redline at ...

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  1. #11
    Senior Member Geeto67's Avatar
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    K0 had a redline to 8500rpm
    K1-K6 had a redline at 8000 rpm
    F/F1 had a redline at 8500 rpm
    K7/K8 had a redline at 8500
    The 76 K6 and F1 were the only ones to have a light green face
    Some of the early dark green gauges have faded and appear to go blue

    here is the sohc gauge spotters guide:

    http://www.sohc4.us/forums/index.php?topic=6961.0

    Something tells me you have cb550 gauges on a cb750. If that is the case the cb550 and 750 have way different tach drives and are not interchangible. At idle they will be close to accurate but at WFO they will be waaaay off. The later cb550 big gauges (75 and up) are very similar to cb750 gauges and it is easy to get them confused.

    the closest I could find to what your gauges should look like are these k2 gauges:



    The cb350F and 400F had 10,000 rpm redlines and also use different tach drives from the cb750. The gauges are smaller than stock but will still fit the mounting bracket. The big 550 gauges look almost identical except for the 9500rpm redline.


  2. #12
    kawiracer's Avatar
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    here is a pic of my gauges, i guess they are from a 550 then, 9500 redline.



    My CB750 Project:
    https://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739

  3. #13
    Senior Member Geeto67's Avatar
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    yup - 1976 cb550 speedo and tach. I didn't even think to ask about the speedo but all SOHC cb750 speedos read up to 150mph, the 550s read up to 120. You can see how similar they look to 750 gauges but they are not.

    The speedo should be accurate, almost all jap bikes use the same oddball speedo ratio (2240:60), but the tach is way off. cb750 tach ratio is 4:1 where as the 550 ratio is somewhere in the neighborhood of 3:1 or some fraction there of. Either way it reads way higher on a 750 than accurate.

    my advice to you, get the correct tach pronto. who knows what kind of damage you can do without knowing where the proper redline is.


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  5. #14
    kawiracer's Avatar
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    ill get one as soon as I can. i have an extra set of gauges ill look at the see what they are from.

    how will the mini gauges listed on this site work, they have the correct speedo, but the tach says 1:4 ratio will that work with the 4:1?

    http://crc2onlinecatalog.com/chopper.htm

    My CB750 Project:
    https://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739

  6. #15
    Senior Member Geeto67's Avatar
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    sorry I had that reversed. The mini-gauges work ok. If that is really the look you want. I had a set from JC whitney and they fell apart on me but they were the cheap-o ones. those look a little better.

    If you are going right to an aftermarket gauge, I would get a dwell meter and check the rpms electronically. Every dwell meter has the setting to do this and a good quality one costs $30 from sears. Plus you can use it to set the dwell on the cb750 points which is always good.

    you can go to an autometer tach as well (or any other electronic tach for a wasted spark ignition) but those are pricey.


  7. #16
    kawiracer's Avatar
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    i think im gonna go with the mini gauges, im gonna get clip ons and i think the stock gauges look too bulky with the lower bars. ill check out the dwell meter.

    i am leaking some oil from my clutch cover, it leaks a little and itll smoke a little from the leakage burning, it seeps a little on and off depending on how long im running the bike, should i be that worried about it?

    My CB750 Project:
    https://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739

  8. #17
    Senior Member Geeto67's Avatar
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    while the clutch cover gasket is one of those few gaskets you don't have to pull the motor to replace, when you buy your gasket kit and see all the pretty new leak free gaskets then you will want to install all of them.

    My advice? if the motor is not currently leaking any oil from the cylinder block area, then buy a gasket kit and just replace the clutch gasket. If you are so inclined, when the first snowfall hits you may want to pull the motor and replace all the gaskets, but be forewarned, the little seals inside the block for the oil return are a huge pain in the ass. but for right now do the days worth of work and just replace the clutch cover one.


  9. #18
    Senior Member pampadori's Avatar
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    gaskets? what the hell are they? i grab a tube of my trusty 3m brand clear sealant for EVERYTHING that needs to be sealed. including exhaust manifolds and turbos. that stuff is incrediable and you can't see it because its clear. just wipe away the excess.

    '72 cb750
    '76 cb550

  10. #19
    Senior Member Geeto67's Avatar
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    Most japanese engines are put together with hondabond, yamabond, or kawibond. however there are still some parts that have gaskets or orings. Typically SOHC cb750 oil pans have a gasket and you don;t really want to put sealer in an oil pan or a carb float bowl. a) it makes it hard to get off and B) you don't want any excess mixing with those fluids and gumming up the works.


  11. #20
    kawiracer's Avatar
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    yeah, there was some kind of glue holding the gasket on that i took off. I dont know what it was, do i need to use some kind of gasket sealer that i dont know about or just the gasket alone.

    My CB750 Project:
    https://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739

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