Revs /mph

[Gromitdog]

Hi Bobv7

I own a cb 550 k3 and at 60mph = 4500 RPM in top gear the gearing fitted to mine is
Front sprocket 17   Rear sprocket 37  but it does feel that it could do with another gear !

Hope this helps you

gromitdog

[Johnny4428]

That’s axactly what I thought gromitdog. I wondered if it was just after riding around on my touring bike.

[bobv7]

Guess it's all down to the gearing inside the rev counter body and not as I had hoped some logical correlation with road speed. Somehow I doubt I'll be risking the engine the way I ride so maybe it's not quite as vital a tool as it was when I was younger! Cheers for the feedback.

[paulbaker1954]

See the post here where I worked out the whole thing👍👍

http://www.sohc.co.uk/index.php/topic,14633.15.html

[Mr Helicop]

on my 550F I am getting 4000rpm at 55mph with 17/34 sprockets - I dont think the tacho is very accurate on these bikes though.

[Johnny4428]

Hi, Just had a good run on the K3 apart from losing the trim off one side of my tank, only to find it run over several times on the return journey. That aside I stated previously that I thought that I was at 60mph at 4000rpm and that is exactly what my clocks are telling me. I will check my sprockets and see what they are, but I have no way of telling if the clocks are accurate.

[bobv7]

Well thanks to the info received I've calculated that if I multiply my rev counter reading by 1.3333 it will be correct.

That is 60mph @ 3000rpm in top x 1.3333 gives a true reading of 3999.9rpm.

I'm sure that must mean something significant about the gearing inside the rev counter head, and I dunno how it helps but it was something to ponder on rainy day.

[davidrsmith]

Hi,
I own a 1977 CB550K3 which was originally registered in the US.
At 4000 revs in top gear it is doing 50mph.

Dave

[robvangulik]

I will check my sprockets and see what they are, but I have no way of telling if the clocks are accurate.

GPS?

[JezzaPeach]

Just spotted this slightly old thread.
I wanted to check my newly damped tacho and nearly bought an optical tacho for £10 but there is a strobe phone app called Strobelight where you can set the rpm at say 2000 and then shine the phone light on the timing nut and play with the revs around 2000 until the nut appears stationary.
I’ve only tried it briefly but mine shows about 2,300 on the tacho at 2,000 on the strobe.
At about 5,000 on the tacho my Speedo reads about right anyway. I think if I set the strobe for say 1,000 the tacho would be about 1,300, which I will check sometime.
Slightly fiddly but cost £0!

[Trigger]

Out of the 10 SOHC's i have only one is spot on with the speedo and rev counter 

[JezzaPeach]

I darent take my eyes off the road after all these years!!