Forum

[papasmurf]

When it comes to the bhp reaching the back tyre I want to see the readout from the testing machine.
The first bike to do a 100mph lap of the Isle of Man TT was a 500 Gilera producing a mere 72bhp.
Plenty of 100mph plus capable motorcycles were only around the 40bhp area.

[PeteF]

And, of course, bhp isn't the only thing that matters; there's the torque to take into consideration. I know enough about torque to not try to explain what it is (and please, nobody else either)
There's also the question of where the bhp is measured. My standard 350 is quoted at 19 (I think) but there is nowhere near that at the back wheel. 19bhp at the crank - possible; at the back wheel - somewhere about 13 I should think.

[jefrs]

Here we see the Bonneville bike was probably an EFI-500 in a CGT frame rather than a 535.

http://www.autocarindia.com/auto-galler ... ageGallery
I'm rather guessing Matt Capri had run the bike up on a dyno to obtain his figures. The DBD34, also push rod 500cc could do 110mph, pretty sure the DB34 and the Venom could top the ton as well. So why don't they hold the record? I reckon there's more to it, such as gearing, than just horse power; did they hit the rev limiter?

[papasmurf]

Jefrs, the full fairing shown at that link is a bit of a clue.

[jefrs]

Papasmurf, I think maybe you got me volte face, the Goldie was raced with full fairing and lapped tracks at over 100mph, that's with wiggly bits and not in a straight line. So I reckon the RE Bonneville bike should have been able to go quicker. Dunno, has no one ever taken a racing Goldie out there?

[papasmurf]

Jefrs, on 5th gear years ago they did and item about Tiff Needell and Vicki Butler Henderson doing a track day on Honda CB600RR's. To my great amusement when they were both going around a tight corner a Norton International overtook them on the outside.

[Adrian]

Now that would be worth seeing - did it ever make it to youtube? A.

[jefrs]

This one? At about 3:22? https://www.youtube.com/watch?v=jXJ9y1qaCvg

[Adrian]

Yes, that would seem to be the one, thank you. A.

[jefrs]

Something Paul (Bullet Whisperer) said earlier, "I would not go higher than 18t on a 500 Bullet, unless it was tuned to a pretty high level". I agree with this so don't get me wrong



The current Bullet has a 19-in wheel with a 17T but the current Classic has an 18-in rear with an 18T, as standard. Wheel diameter ratio is roughly (add tyres if you like) 18:19 which is approximately one cog, because you can't have half a cog.



My C5 is slightly tuned and I do find I want to 'change up' from 5th around 60 but, big but, I find its current top speed of somewhere north of 75 to be exciting enough. The only drawback is taking the bike on anything resembling a motorway. I do not want to degrade acceleration but it has such a wide power band I don't think it will notice an extra cog. First gear is low enough to pull from whatever speed I can hold it upright and I can practically track-stand it. It will pull away in 2nd but that one is possibly a little too high especially for hills or two-up. In other words it could take a higher ratio first gear, was this 'box designed for pulling a chair?

The alternative to changing the gearbox sprocket is fitting a bigger rear tyre, roughly half a cog. Has this been tried, with what result?



Otoh, bearing in mind that speedo and tacho (Smiths on mine) are a bit 'indication only', 65-70 is just over 3000rpm in top. The big power band is supposed to be 4000-5000 with 5500 red line. So why is it running out of steam below 4000?

Personally I need to understand this performance issue before even considering changing its gearing.