CBX Racing

[Rick Pope]

It would take more than a chain driven jackshaft, that would accomplish nothing. To reverse rotation would likely mean gear drives. A gear driven jackshaft might do it, or not, depending on number of gears.

[Warwick Biggs]

Agreed Rick, it would have to be a shaft. Chain primary drive would have to be replaced with a shaft but then in a typical twin shaft gearbox the motor would have to run backwards to generate forward momentum.

I have put out a query to Team Obsolete on their RC 164's primary drive. If anybody else has any knowledge on the subject or can provide any good technical links on the Honda 6 cylinder racers primary drive I would appreciate it. The more I look at it those motors looks like two in line triples, as does the CBX.

Assume a shaft primary drive and pinion gears in place of sprockets and all the above. What else would have to change? If you simply reverse rotation what mechanical and timing changes would be involved?

[Warwick Biggs]

This pic of an RC166 motor might help. Note the layout of the crank and jackshaft. Putting the take off in the centre also reduces torsional twisting of the crank.

[Rick Pope]

A little more thinking.......Forget about it. Not only would you have to convert to gear drive, but you'd also need reverse cam timing, and then the cam chain adjusters wouldn't work as the slack would be on the wrong side, etc.

I'm not saying it's impossible, but highly impractical.

[Warwick Biggs]

That is not an insurmountable problem as the tensioners could use some improvement anyway but I'm more interested in the 'etcetera'. Everything else would simply operate in reverse. The CBX already has a jackshaft so it is just a matter of changing from belt to gear drive isn't it? The fundamentals already appear to be present. They would obviously need adapting. The valves would open and close in the same order and the pistons would also rise and fall in the same order but just backwards. It seems to my simple technically illiterate mind that the only thing that would need to change is the ignition timing depending on the pickup.

This is really just a brain teaser but what am I missing? Do we have an engineer in the forum?

[Warwick Biggs]

I should add that I have never forgotten my experience with a 2 stroke TZ racer that had an early Krober ignition. In those days we had push starts and sometimes it would start backwards with a predictably dramatic impact on the rest of the grid. 4 strokes are a bit more complicated.

[bobcat]

Please explain how to reverse the rotation direction of the transmission
and final drive.

[EMS]

It has been done. When Andreas Georgeades built his V12 CBX, the additional cylinder bank rotated backwards.

[bobcat]

It has been done. When Andreas Georgeades built his V12 CBX, the additional cylinder bank rotated backwards.

But that did not change the rotation direction of the crank/final drive.

[Warwick Biggs]

You do not want to change the direction of the final drive unless you like riding backwards but you do want to change the rotation of the crank from clockwise to anticlockwise in order to neutralise the gyroscopic effect of the crank and wheels all spinning the same way.

Interposing an additional shaft allows this to be done whilst maintaining the same gear cluster. There is a small loss in mechanical efficiency but the turn in and handling benefits outweigh the slight loss of efficiency. This whole notion is really only relevant to longer crank engines in racing where handling is more critical than outright power. An alternative approach is to shorten the crank and centralise the mass, moving the centre of gravity as far forward as possible and reducing the gyroscopic effect from a longer crank.

In MotoGP all the bikes have so much power that the critical issue now is getting that power to the ground and that is partly down to sophisticated electronics but ultimately about the balance of all the forces acting through the tyres. A bike has a more complicated set of forces than in play than can be found in a fixed centre of gravity, when all these forces are combined.

I think all the across the frame 4's in MotoGP now have reverse rotation cranks.

I had to cannibalise the front brake master cylinder off the CBX yesterday when I lost my brakes on the NC30. Luckily it happened on the dummy grid during practice for the Championships and not during racing! The banjos fitted so it bolted straight on but the bore ratios are obviously not the same because it is very snatchy and I've had to change my riding to suit. I'm about 3 seconds a lap slower than my best but at least I managed to improve my grid position in the first race today. I have another 3 tomorrow and if I'm consistent and finish all in the same position I should be a chance at a podium. I have learnt the hard way not to cable tie my front brake for long periods.

[Rick Pope]

It has been done. When Andreas Georgeades built his V12 CBX, the additional cylinder bank rotated backwards.

Yes, and he used a gear cam drive from a VFR. I don't recall what he did for cams. Just running the stock in reverse would give very poor results. Would it run? Probably. Would it make reliable power? Certainly not. Timing would be all wrong, opening and closing ramp geometry would likely ruin buckets and spit shims.

[Warwick Biggs]

I am happy to report that today after 3 races and another 3 consecutive and consistent seventh placings in a mixed unlimited P6 grid we managed a consolidated 3rd in P6 500. Altho' it was a depleted grid with many entrants piking out due to C19 we were still up against an immaculate and well ridden ex factory WSBK RC 30, a swag of much faster RS250's and TZ250's and some top riders from around the country. In my class I came in behind an FZR400 (could be bigger???) but well ridden by a very fast ex125 racer and a slightly faster and again very well ridden CB400, both with much younger riders.

So, while I was hoping for better results I can't really complain after some tough jousts and very close calls. While it is axiomatic that a bad workman blames his tools we did have a few problems including very snatchy brakes (out of ratio CBX master cylinder hastily replacing a 14 bore NC30 that was cactus) and that entirely precluded any trail braking. Then there was the gradually worsening internal leak that was pressurising the 2 radiators and overflowing the coolant catch bottle, not to mention 40 degree humid temperatures on Saturday. But we survived more or less intact altho' the Lump is temporarily missing it's master cylinder.

Between now and April we have to strip the NC30 and fix the leak (suspected head gasket, hopefully) and install the race motor in the Lump. Roly has the bits almost ready so that will involve dragging the bike over to Melbourne and significant dyno time, in readiness to run both bikes in the National Championships. When I have time I will post some pics of the SA Championships.

As for spitting shims that will happen anyway once you hot up a CBX unless you do an under bucket conversion and while my brain teaser is purely academic, nobody has come up with a solid reason why it could not be done.

[Syscrush]

nobody has come up with a solid reason why it could not be done.

That's because anything can be done.

In a shed, with a hacksaw and files - provided your name is Allen Millyard.

[Warwick Biggs]

Yes Phil, so it seems after securing P3 in Period 6 500 of the State Championships, with dodgy brakes and pissing coolant everywhere!

Who is Allen Millyard?

[NobleHops]

<boggle>

Go ask the Google Machine. Pour yourself a whiskey first, and have an hour to spend.