SOHC.co.uk Forums > CB350/400

Might have to repaint the red zone on the tach...

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Mikep328:
OK, not really but last week I was out and going through the gears to redline and missed a shift at full throttle into 4th gear and saw the tach whip past 12k RPM with absolutely no ill effect in the remaining 50 miles of the ride.

I was talking about that with a vintage Honda race tech guy here on the Isle of Man - we're here for the Manx GP - he said that the "Honda rev limiter" back then was valve float which would essentially "shut off" the engine when the RPM got to the "float point."  He said valve float would occur long before engine RPM could hurt anything.  He seemed to know what he was talking about since he was one of the techs preparing vintage Hondas for the races here. 

Oddjob:
Can’t say I’ve ever heard that theory Mike but I wouldn’t like to test it. I reckon valve bounce or a chain failure would occur first. Either way it turns out expensive, going through the red isn’t the end of the world and on a well maintained engine shouldn’t cause any harm, on an ill maintained engine it’s asking for trouble.

Athame57:

--- Quote from: Mikep328 on August 27, 2026, 10:22:02 AM ---  He seemed to know what he was talking about since he was one of the techs preparing vintage Hondas for the races here.

--- End quote ---

I think that status would introduce caution with me, such a person could have a very different mindset to the average owner. Getting it through the race in record time is probably the important bit, not the bikes ongoing health!  :o

Bryanj:
I remember reading an owners handbook, earlyb500 four i think, where it said not to go outside the red at the top, i can also remember an older Honda team rider who being walked over by Mike Hailwood on his return to the I.O.M was reputed to have pulled in the clutch at full chat till the valves bounced!

Sesman:
Mmmm. 12000rpm without any ill effects. How do you know? I’d be more concerned about the potential stress damage you can’t see without a granular, detailed check. Consider going to 12000 again for about 5 seconds and let us know how you get on?

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