33bhp malarky

[rob_scott92]

Hey everyone,

yes that's right, yet another restriction question for ya

I've been looking at possibly getting a cb 350 sg once I've passed my test and there's something bugging me a little bit.
I'm finding it hard to find an exact power output for the bike, so I was wandering, if it is something like 35hp, could I argue that it's lost a few since it was built (80's bike) or would I be told I'm effectively riding without insurance yada yada?
If that is the case, surely I wouldn't have to pay out for a restricted kit over 2 bhp?
Thanks
Rob

[Ingah]

The law states your bike must be 33BHP. It does not state whether this is measured at the wheel (dyno'ed) or at the crank (as far as i know this is impossible to do bar dismantling the bike - and it is the higher figure of the 2). Providing you meet this ambigous requirement, you are technically legal.

Obviously this does not stop a copper trying to prosecute you for the alleged offense (i doubt those that know about the 33BHP restriction will know the exact wording of the 33BHP law and so an arse that takes a dislike to you may well try it on), just that in court with a solid defence (i.e. not just rocking up on the day and bleating at the judge) i'd fully expect you to be "innocent".

If cops dyno your bike and it reads over 33BHP, it's safe to say you're screwed as this would be sufficient evidence. I'd be surprised if it was over 33BHP, but i don't know much more than hearsay about bike mechanics.

Interesting thought is what would happen in a major crash regarding insurers (where they have a vested interest in wriggling out of their responsibility) as the balance of probability is legally for them to prove you were riding outside your license if it comes to crunch time. They would be able to prove lack of restrictors though, but not BHP (if it's that bad a crash - but i'd probably say that be the least of your worries in that serious a smash). Regardless i wouldn't like to be that test case, slippery eels that insurers are.
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-- Ingah

[Kickstart]

Hi

Think the wording for the 25kW / 33hp limit is "net power output", and I suspect that is trying to mean the crank figure. Which as mentioned above is virtually impossible to measure (you can come up with an estimate based on the rear wheel figure and measuring the drag from the gearbox, etc, but no way to really be certain the drag is the same on the gears with the load in one direction or the other, let alone the drag from the primary drive that is eliminated when the clutch is pulled).

With a 1980s bike I, whether the bike has lost power or not I wouldn't expect the claimed figures to be accurate anyway. Suspect they are more related to the marketing department than any technical departments.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[rob_scott92]

Ok thanks, I understood most if not all of that

Think when i pass my test and inform my insurance company i'll throw a few hypothetical bike purchases there way, as i believe they know power outputs for bikes and such?

Also, am i right in saying that the Kawasaki GPZ305/250 have, lets say, pretty piss poor engine design?

Thanks for the info
Rob