Revs /mph

[bobv7]

Afternoon All

Can anyone tell me what rpm I should be reading at 60mph in top?

Cheers

[deltarider]

CB500? 5000 rpm.

[bobv7]

The reason I ask is because I bought an after market matching speedo and tacho. The speedo looks like it's reading pretty close as they usually work off front wheel diameter anyway but I'm not so sure about the rev counter, but since I'm not going be red lining the bike every where it's not so important. There is a marking on the rev counter dial reading 1:4 so maybe it was intended to fit a twin and actually showing half the true rpm?

[Johnny4428]

My 550 is 4000 at 60mph.

[deltarider]

CB550s vary, some have 17 and 37, some have 17 and 34 teeth.

[Johnny4428]

Just had a look at mine it looks like 36 rear. So the least teeth on the rear the faster for same engine rpm?

[robvangulik]

4000 rpm at 60 mph is about the same gearing overall as a cb750, isn't that a bit tall for a 550? 120mph at 8000rpm?

[Johnny4428]

I haven’t had the speedo or tachometer calibrated or refurbished other than new faces and painted, so cannot confirm accuracy. It maybe slightly above 4000 at 60mph. I will check tomorrow if the weather is kind.

[Seabeowner]

I put the various numbers on an excel spreadsheet.
Gearing between the crank and the primary shaft is the same on 500/550.
Gearing between primary shaft and clutch basket is different. Overall primary gearing 500/3.247,  550/3.063.
1-5 gear ratios are the same.
Standard front/rear sprockets are 500 17/34,  500 17/37. Delta says some 550s may be different, but I have no knowledge.
Rear tyre standard, 500 is 3.50,  550 is 3.75. Changing from standard sizes will alter gearing to rear and accuracy of speedo on front.
All in all the overall ratio on 500 to 550 is just about identical.
Should be 4000rpm = 51MPH. 6000rpm = 76MPH.

[deltarider]

Delta says some 550s may be different, but I have no knowledge.

The CB550K3-ED, say for continental Europe, had 17 and 34, like all CB500 models had. It was to market this particular model more as a tourer bike, to differentiate to the somewhat sportier CB550F2. In the rest of the world all CB550s had standard 17 and 37.

[philward]

The reason I ask is because I bought an after market matching speedo and tacho. The speedo looks like it's reading pretty close as they usually work off front wheel diameter anyway but I'm not so sure about the rev counter, but since I'm not going be red lining the bike every where it's not so important. There is a marking on the rev counter dial reading 1:4 so maybe it was intended to fit a twin and actually showing half the true rpm?

I fitted a pair of aftermarket matching rev counter/speedo to my 750 K2 just after I rebuilt it (while I was refurbing the original clocks) and the the rev counter read about a 1000 rpm high at 60mph

[bobv7]

Anything like these?

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[philward]

No, they where CB750K replica's (almost identical to the original's to the non expert) 

[Johnny4428]

That is interesting on the proper gearing numbers. I didn’t get out on the bike yesterday not weather in the morning so decided to fit new fork seal that seemed to be leaking. (Can’t believe somebody put the one seal upside down) ooops!🤭🤫!   I am now starting to doubt myself with mph/rpm, wouldn’t be the very first time I have been wrong.😂

[bobv7]

Riding the bike this morning and the rev counter was reading 3000 rpm at 60 mph. Obviously this set up is not a direct replacement for the standard one but it would be interesting to see if anyone can spot a relationship between the readings? I thought the rev counter might be reading half speed but not sure that matches up with what others are quoting. Ideas??

If you missed it this the set up!

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