rear sprocket size

[mickwinf]

Just assembling my rear hub, and I have a new sprocket which is a 37tooth which I believe is a 550 item, the 500 should have a 34 tooth. My question is would it make much difference in the real world if I fitted it?

[McCabe-Thiele (Ted)]

Improve 0-60 time poorer fuel economy?

[Oddjob]

Not a great deal, the primary shaft gear is also different on the 550 and the clutch basket has either more or less teeth as a result, that altered the overall gear ratio but TBH I think Honda put a 37T rear sprocket to improve the standing quarter as there was a lot of competition at the time.

[Seabeowner]

I have a little excel sheet for this:
5000 rpm = 64 MPH with 17/34 and 58 MPH with 17/37. (in top). Also depends on tyres slightly.

So will be revving quite a bit higher.

[Oddjob]

You must also take into account the change in the clutch gearing, as I said they changed it from the 500, IIRC the primary gear had 23T on the 500 but 24T on the 550, that alters the gearing a little.

[Trigger]

https://sprocketcalculator.com/calculate

[mickwinf]

I quite like the idea of quicker acceleration as most of my riding will be on A or B roads so will leave it on, can always change it later.

[deltarider]

What I like about the CB500's standard set 17/34 is that the result in topgear is: 5000rpm = 100km/h, 6000 = 120, 7000 = 140, 8000 = 160 and 9250 = 185km/h.

[Seabeowner]

You must also take into account the change in the clutch gearing, as I said they changed it from the 500, IIRC the primary gear had 23T on the 500 but 24T on the 550, that alters the gearing a little.

You're right the 500 is 23/64 and the 550, 24/63 primary shaft/clutch basket. Everything else the same: 24/28 Crank/primary shaft and all gear ratios.

[Oddjob]

Why I mentioned that was because the gearbox will spin at a slightly different speed on the 550 than on the 500, so the 5000rpm at 64mph might not be true for the 550 even if it had a 34t rear sprocket, with the tacho running off the camshaft the drive train could be turning at a different speed and you'd never know.

On the later Hondas they run the tacho off the mainshaft, you'd get people claiming that changing the front/rear sprockets hadn't made any difference to the speed v revs when in fact if you use GPS speed you'd find the bike running faster or slower for the same revs after swapping sprockets.