CBX Racing

CBXs, new bikes, old bikes, cars, trucks, general chat, off topic, this is the place to post it.
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daves79x
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Re: CBX Racing

Post by daves79x »

I suppose you can tell I'm not a fan of this kind of thing. It's money down a rat hole, that leads more often than not to the disappointment you have alluded to several times. But it's your money and time and I wish you well.

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Syscrush
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Re: CBX Racing

Post by Syscrush »

I wonder if you'd gain any clearance by going to cartridge internals on the forks.

Damping rod forks compress more under low-frequency loads and less under high-frequency loads - so they tend to dive under braking, which will take away some of your clearance - especially if you're trail braking, which would be common at the track.

With good cartridge forks that don't dive so much under braking, you might gain a few precious mm.
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Re: CBX Racing

Post by Warwick Biggs »

I have to agree Dave that the idea of turning a heavy production road bike into a racer is crazy.

Having admitted that, I have to say I was inspired by Roly's efforts with The Beast (everybody thought he was crazy too!). When I began I never imagined I would ever be able to race it and it was more a therapeutic exercise than anything else. We have come a long way since then both with the bike and my own physical capabilities. I am now pushing the bike well past where any road rider might think of going.

The class in which I race is the historics . It is a silhouette class based upon period and some basic appearances. The CBX runs in P5 unlimited - the last of the air cooled super bikes. As such there is a high degree of aestheticism. I always liked the Bol Dors and the CBX is basically a Bol Dor on streroids. I'm just happy to run around on it and dice with other old bikes. I like the look . I like the sound. I like the way it goes. It is fun to ride these things fast - hadn't you noticed? It's even more fun to ride them to their limits and beyond; which is where I am - beyond! And it is something different - certainly a 'look at me' bike. Sometimes not very charitably.

It is axiomatic that when you race you always want to go quicker. That is quite a challenge on the CBX and partly explains why there are so few racing. I do it on a pension so my budget is a tiny decimal point of the likes of the Irving Vincent team and my mechanical abilities are all self taught, side of the road, by myself struggles but over time I've accumulated a fair bit of experience.

I've raced a pukka GP bike when I was young. That is not my scene anymore. I'm just out there having fun, challenging myself as much as any others.

Now Phil, the cartridges may help but I doubt they will solve my clearance problem. My forks are modified by Trevor Manley - a multiple national champion and somebody who worked with Nicco Bakker developing GP chassis and suspension tech. He also rode Roly's Beast and is very familiar with the CBX on the track.

If I can't solve the problem by jacking the bike up any further then the next simplest and cheapest solution is to go back to 18" wheels. I would really like a set of Dymags. If anybody would like to donate anything to one of the few CBX's still racing and you don't mind being accused of craziness a set of 18" Dymags would help a lot. Or, I could try to emulate John Britten and make a set of carbon fibre wheels. People thought he was crazy too!

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NobleHops
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Re: CBX Racing

Post by NobleHops »

Rick, I think you could possibly take a different approach to the clearance problems, and that’s through refining your riding position. During my short but earnest career as a club racer on production-spec bikes I was running out of clearance left and right, mashing my feet between the pegs and cases, dragging the exhaust in some cases. With some coaching and some added strength in my legs I really worked on hanging off, with a much lower upper body, putting my head above the stock clip-on and with not much more than my thigh on the seat. And that made all the difference. After I got stronger and better at that my lap times went down and the only time I touched hard parts was when I was crashing.

I’d have a hard time with the physical demands of that at my age and you’re a bit older than me - but that’s an avenue for improvement that might keep your bike off the deck a bit better.

N.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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Re: CBX Racing

Post by Rick Pope »

Good point Nils. A former member (and good friend) here is a coach at racing schools, and club racer. His street bike tires are all chewed up but he has big "chicken strips". He hangs off pretty far. Don't know his age for sure, but I believe he's late 60's.

I, otoh, sit like a lump and enjoy the scenery.
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Re: CBX Racing

Post by Warwick Biggs »

Well, you are not the first to suggest that Nils but I do move my weight into the corner as best I can. I am fairly fit for my age but 4 races in a day still leaves me utterly exhausted and I usually return to the pits sweating profusely, irrespective of the weather.

That raises another issue. Racing is the main reason I have cut down on alcohol. I play competitive tennis at least 2 or 3 times a week to keep my weight down. My partner accuses me of becoming dull and reckons she's a widow to the bikes. I've flirted with yoga to improve flexibility too and I have been coached by some of the best (many of whom were just a sparkle in their parents' eyes when I first started racing) but Trevor Manley's advice rings loudest ... "try harder".

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Re: CBX Racing

Post by Warwick Biggs »

Here is a nice professional shot of the Lump at the National Championships together with a pic of me to prove that I'm not always a miserable grump complaining about CBX's. I'd probably just come in from one of the Senior 500 races (where I would have done better if I hadn't missed qualifying while I was trying to fix the CBX and then had to start at the rear of the grid). I still had some great dices and finished with 2 PB's, so it wasn't a complete fiasco.
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hondaman160mph
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Re: CBX Racing

Post by hondaman160mph »

Anyone ever raced a Spondon or Moto Martin framed CBX on
the track? I'm curious as to how they sort out compared to
the stock factory frame.

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Re: CBX Racing

Post by Warwick Biggs »

Me too. Georges Martin has and his race frames are designed to run 18" wheels, not 17's. The trouble is finding light weight 18" wheels.

You can buy fancy wheels for dirt bikes and Harleys but strong light wheels for classic racers are ultra exxy. Easier to find for Euro bikes than Hondas (eg: Borannis but they are spoked and probably would not handle the weight of a CBX).

The Honda Big One CB1 had 18" wheels and compatible sizes but they were only sold for a short period in the 90's and are relatively rare birds. I know a farmer wo has one but he won't sell it for love nor money.

I have a set of 18" Boomerangs that I could revert to but they are very heavy and a bit skinny making it a trade off between less traction and speed versus inadequate ground clearance.

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Syscrush
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Re: CBX Racing

Post by Syscrush »

The Bull Dock Lavorante wheels are forged aluminum and available in 18" - is that worth looking at?

https://japan.webike.net/products/21437043.html
Phil in Toronto
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Re: CBX Racing

Post by Warwick Biggs »

Yes, but every time I seriously consider what seems a simple solution it ends up involving considerable thought because apart from the significant expense of the wheels themselves, the Lump is already so modified that it quickly becomes complicated. It goes well beyond simple rim diameter. Width has to fit the rules as well as the bike. I have Jyo Bito's Magtan brochure but would have to sell both kidneys to afford one of his wheels.

Even going back to the boomerangs that I still have would involve significant modifications. The front has since been modified to run a VTR front wheel and modified rotor. The rear is no longer Honda but uses a ZZR rim and caliper. Both mods were cheap and sourced from the wrecker's yard. Issues include the correct bearings for the axle, alignment of the chain, sourcing a suitable brake caliper, matching bolt patterns/rotors and machining up new spacers. It is certainly not straight forward. Then it inevitably leads on to thinking about ditching the Prolink swingarm for a wider rear wheel and then you may as well go for a whole re-design of the back end but it still has to look 'period' and it is all getting too far away from the original Prolink and my personal philosophy.

This ultimately takes you down the replica path. Essentially that involves starting with a modern superbike made to look vaguely like the original and retro-fitting it to look 'period' - just like the Irving Vincent.

I think I will keep experimenting with suspension/ride height and riding technique for a bit longer to avoid the headaches posed by changing wheels again. There is a limit, even for me!

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Re: CBX Racing

Post by NobleHops »

Technique is the solution.
Nils Menten
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Re: CBX Racing

Post by Warwick Biggs »

Not for the first time we can blame tyre technology for my problem with ground clearance. Look back to page 74 of this blog and put a protractor on the pic of the NC30 in the Office Corner. It is around 60 degrees. Marquez and his cohort slide around at even more physics defying angles of lean.

When Ken Roberts turned up in Europe with Goodyear slicks it changed the motorcycle racing world. Street bikes designed in the 70's like the CBX were never imagined to be capable of such performance. It was simply well outside the design envelope.

I used to advocate for a rule that historic bikes must race on historic tyres. Not 40 year old tyres (can you imagine?!) but slicks should be banned. That failed because the ripost was that slicks were available in the period up to 1980, the P5 cut off date. So then I switched tack to a limit on tyre size where I enjoyed a measure of success and helped stop the push to 6" rims. 5.5" rims had already been accepted so that was a harder nut to crack and that is what I currently compete against. A Prolink swingarm is at its physical limit accommodating a 165 rear tyre so that is my self imposed limit. Most of my competitors race on 180 or 190's. I could employ a wider arm but then it would not be a Prolink - you can see the paradox.

After more thought than is probably healthy I have concluded that my main problem at the Nationals was not just ground clearance or lack thereof, but the vicissitudes of racing. I had a bike with an entirely different nature as a result of the substantial power increase. But because of the last minute problems with the rear brake seal I lost my opportunity in practice to sort out various issues like adapting to the new character of a bike that I had not ridden for over a year anyway. I tended to ride it like I ride the NC30 which is simply wrong technique. So, yes Nils, you are correct to a point. But lack of preparation and practice time was at the heart of the problem. It was a timing conundrum.

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Re: CBX Racing

Post by Warwick Biggs »

Speaking of the rear brake master cylinder, I am having trouble getting fluid through the master cylinder after refurbishing it with a kit. I pulled my temporary 'track fix' Nissin m/c off and reinstalled the original CBX m/c with a new piston, spring and seal but after ages priming (thumb over top banjo hole) pumping and brake fluid mess everywhere I still have no pressure.

I tried pushing fluid thru' and up from the rear caliper with a syringe and whilst it filled the reservoir OK it somehow did so without dislodging all the air from the m/c. Does this suggest another problem to anyone?

I have perused the various threads on rear m/c problems and am awaiting delivery of a mity-vac (why do we have so many holidays that delay getting anything done quickly? Obviously, a retiree gripe) but am loathe to pull it all apart again. I did it once just to double check that I had installed the seal pointing the correct way. I had.

The 2 screws that fix the reservoir tube to the m/c show signs of past butchery and look to be too small for my impact driver so I'm loathe to touch them or investigate the holes in the m/c. All I can say is fluid made its way up to the reservoir.

Meanwhile, I pulled the CR carbs off and cleaned all the jets. The usual hassles getting them all back on again with rubber grease everywhere (altho' not as bad as the straight bank that I used to have) and noticed the cable nipples are not seating straight so I will be fitting new cables too. I have also relocated the auxiliary throttle spring so it only works at full throttle. The main spring on the JB CR's is quite strong but still not strong enuf' to overcome the venturi affect of 6 wide open throated carbs. The push cable and extra spring are necessary to avoid the throttle being stuck wide open at full blat going into the first corner at the end of the straight. This 'stuck throttle tendency' has been exacerbated by the increased compression and capacity

The heavy springs also contribute to a fairly stiff and heavy throttle at the grip and combined with the Venhill quick action throttle cam, make smooth throttle control rather difficult. This is another factor contributing to missed gear shifts. Stock CV's are feather light by comparison but useless for racing due to the vacuum delay. As usual, fixing one problem seems to cause another!

In readiness for the Seniors races in 3 weeks I have raised the rear ride height by a few mills as mentioned earlier and dropped the forks a similar amount. In order to fit a set of lever protectors to the clip-ons I've machined down the internal expanding collars and I will fit new grips to replace the worn ones (worn out after half a dozen races tells you how stiff the throttle is). Lots of little jobs altho' the rear brake seems to be particularly problematic. As always, any suggestions or opinions on my brake query above would be appreciated.

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Re: CBX Racing

Post by NobleHops »

Rick,

With a good master cylinder, the rear setup usually bleeds in a minute, literally. If yours will not, and assuming you nave a good seal at the banjos, then I will say in high likelihood that your MC is toast, and too pitted to seal. And that's common.

My 80 CBX has the best brakes of any CBX I've experienced - they are twin-pot calipers and rotors from the 80s CB-F and VF bikes, and I am convinced it's because I had my front master cylinder sleeved many years ago, in concert with the twin-pot calipers and steel lines. And so my free advice is to bin that MC and replace it with a good used one, or get it sleeved in the off-season.

N.
Nils Menten
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