Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Mikep328 on August 27, 2026, 10:22:02 AM
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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.
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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.
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He seemed to know what he was talking about since he was one of the techs preparing vintage Hondas for the races here.
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
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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!
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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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"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?"
I wasn't suggesting that going to 12k was a good idea, just that the occasional missed shift at full throttle won't blow up the motor!
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I don’t think for a second Mike that you were advocating revving one to 12000. Plus I don’t think the rev zone goes up to 12k even past the red zone, maybe 11k, been a while since I looked.
You should also bear in mind this mechanic is used to working on race bikes, not street bikes. As such they’ll have race cams, different valve springs, different compression ratios etc. They’ll rev to 12k quite safely, probably 14k.
A few missed gear changes won’t hurt an engine unless you hold it there, a few minutes running in the red most likely won’t either, I did that a lot when I was racing. As the years go by and all the internals age, then like our bodies I’d take it easier on it rather than the other way around.
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I know, just my mischievous sense of humour🫢