SOHC.co.uk Forums > CB500/550
Partially Restored 74 CB550
McCabe-Thiele (Ted):
I've obviously missed something as I never saw your rev counter except briefly in a video so amazed that DR spotted it was a 750 unit. Amazing how we can make ourselves believe a Gauge reading even though it feels wrong in our heads at least for a while.
It reminded me of when I first had my old Honda 250 Super Sport after the 250 Dream - the engine speed always sounded much lower than the rev counter reading as the two firing strokes were closer together on a 180 crank than on a parallel twin. All I heard was the one firing bang as the two power strokes were closer together. I suspect the smoother balance of a 180 crank helped make the revs seem less than the needle was reading.
davidcumbria:
Agreed Ted. I thought I had previously confirmed the tacho was ok using an old a test meter but probably got the scale interpretation wrong due to this engines confusing wasted spark and crank speed points drive.
I don’t think there is a fix for this while retaining the 750 tacho but pretty sure I can live with it now I m clued up.
Was kind of musing about doing a super dream as my next resto…
McCabe-Thiele (Ted):
Although my a Super Sport was a slightly more modern with a round headlamp not square I much preffered the standard 250 Dream. It was easier to live with on a daily commute not needing the constant gear changes.
As a young man of course the Sport version meant it was faster, it had more students looking at it in the bike shed. Oh the shallow naivety of my youth. 😁😁😁
deltarider:
Actually it wasn't difficult to spot. I have heard enough CB500 and 550s in my life. On hearing the sound and a quick glance at where the dial was, I concluded: this can't be right. Then I had a look where the red zone begins.
So it was the sound in combination with the rpm the dial indicated.
davidcumbria:
It also explains why, as mentioned in a previous post, at a supposed idle of 1100 rpm my timing mark when strobed had already moved off the F mark because it was actually revving at 1700 rpm. All is becoming clear!
I have looked at trying to convert the tacho which is in good cosmetic condition to read correctly but there seem to be conflicting opinions. . I reckon Camshaft tacho drive can’t be swapped but is there a gear drive in the instrument itself that could be swapped from a rough 550 eBay tacho ? Not sure how the internals of a tacho work. I’ve read enough to decide that if it requires opening up / re closing the ferrule I won’t be doing it myself.
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