CBX Racing

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

Post by Jeff Bennetts »

Warwick Biggs wrote:
Thu Nov 12, 2020 9:14 pm
I can't help wondering about that inlet manifold. Here is a pic of the Blancquart CBX that looks like it has a pretty stock head fitted with a V shaped bank of flat sides.

If the stories are correct it was revving to 20,000 rpm and making over 200 hp. It certainly sounds like it revs much higher than any CBX's that I've come across altho' I note your past skepticism Jeff.
I've seen the videos of that bike having the snot reved out of it, made me cringe! Pat's bike sounded similar but not as extreme, 146 rwhp is nothing to sneeze at and was sufficient for the suspension he was using!

You mentionen the inlet manifold as crude, maybe crude looking but many hrs went into that head's runner design and execution, pretty wasn't a consideration.

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Re: CBX Racing

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Most of our Period 5 2 valve Katanas are making around the 140hp mark with very conventional tuning and welded up cranks.

But Jeff I have yet to see a pukka CBX racer with anything like 146 hp. 130 hp seems about the limit so far for a practical race bike. So 146 hp is very good and nothing to sneeze at. Maybe that unlovely inlet manifold is actually worth about 16 hp! It is a competitive figure for club racing but no longer really cuts the mustard against the replicas that are pumping out around 200 hp and dominate the major historic races. Having said that I would love to have another 30 hp in the lump, provided it was reliable day in, day out hp. No good having a racer that only works on Mondays. That is why I keep pursuing incremental changes like a set of V shaped CR Specials. WeMoto have them on sale at the moment for half TIMS' price for a straight set but unfortunately they are a Bito factory build and appear to be in Covid induced hibernation and unresponsive.

Roly's more highly developed Beast has an extra 1,000 rpm over my lightly tuned lump but his is a $30K engine and like you I believe there is a law of diminishing returns on tuning. I reckon it would cost me around $1K per hp to follow his route and In the end I think I'm better off spending my money on the chassis and the handling because that is more important to my lap times and riding satisfaction.

Brancquart Competition is still a going concern so I have asked them for more information on their CBX altho' I have opined in the past that it is not an historic race bike.

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Re: CBX Racing

Post by Syscrush »

Warwick Biggs wrote:
Fri Nov 13, 2020 1:39 am
Brancquart Competition is still a going concern so I have asked them for more information on their CBX altho' I have opined in the past that it is not an historic race bike.
It's not any kind of race bike, is it? It's just a rolling advertisement for their company.

I still have a lot of love for it in my heart, though.
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Re: CBX Racing

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Strangely Phil in their latest post on the CBX and for reasons that escape me they have installed a Ducati dry clutch in it. Cooling and drag? It also seems to have an auxiliary crankcase breather connected to the blanking plate for the generator cover. in addition to the conventional location. It makes me wonder about crankcase pressure at higher engine speeds.

As for marketing, it makes the world go round, doesn't it? Roly's efforts with the Beast have generated a lot of work for him after all. Hugh Robinson used his customer CBX projects to promote RPE but for all Brancquart Competition's innovation with the big six they do not appear to have much interest in or connection with the CBX community, which is a bit strange.

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Re: CBX Racing

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Well.. we all know that the limit for RPMs are the valve springs. Valves start to "float" at a certain point and I have to see a design that will work in a CBX head that will safely go over 12,000 rpm.
The limit for hp in the CBX engine is the crank. It will flex and bend if you try to get much over 130hp. There is not much room for improvement there.
I hear all these braggings about Turbo CBXes putting out 160hp +...Sure,,,
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Re: CBX Racing

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My 1990 DOHC NC30 is redlined at 14,500 but you can safely over rev it another 1,000 rpm and my '09 DOHC gixxer is redlined at 15,000 rpm altho' it has titanium valves that are very light weight.

Light weight valves, dual springs and a bucket conversion should allow speeds of around 12K but as Roly has found the rods are vulnerable so a set of Carillos and a lightened and balanced crank are required and dear-oh-dear, that is around $30,000 worth of mods for 130 rwhp.

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Re: CBX Racing

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2021 Island Classic postponed:-

https://woocomcampaigner.woocom.com.au/ ... _VGi417ptA

So we can legally race in Victoria but because of the worsening international situation with the pandemic the international challenge cannot proceed and therefore neither can the Island Classic but this is a mistake. The race should go on and absent friends can just sit at home and watch. Might make for a more honest competition without all the hoopla. After all it started as a local historic bike race for club racers b4 the big money and young professionals took over. In those days the CBX was a leading contender for the podium b4 the faux XJ1200 specials took over.

And our clean Covid slate has been wrecked in an instant in South Australia where they insisted on allowing people to fly in from hot spots like India, Europe and the US and now the genie is out again. Another lockdown and it is becoming a tedious slog. Yet again the racetrack is closed because of complacency, greed and stupidity. I see little evidence that we are really progressing as a species at the moment.

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Re: CBX Racing

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The CBX valve float issue was apparently addressed as follows (quoting Lionel Brancquart):-

"...we have worked a lot on the weight of the moving and rotating parts! we are 55gr lighter (tappet, valve +2mm tige de 4mm, retainer titanium Xceldyne, springPSI, twin cones, pellet) x24 parts all the parts have a surface treatment, the connecting rods are longer and lighter to accommodate piston in 66mm 2 segments and above all we have a very efficient ignition from Emanuel Guyonnet (who manufactures all the ignition for Guy Coulon Tech3)..."

I hope to have more detail to share on this remarkable CBX soon but invite comment on these details.

In the meantime I have rebuilt the rear suspension on the GSXR, spaced it up for more ground clearance (CBX's converted to 17" wheels are not the only sports bikes that scrape) and gone from a 9 kg/mm spring to an 11 to handle my 90 kgs (I have to lay off the bubbles and get back to 85!). Just waiting to get baclk out on the track to try it out. In fact all 3 of my race bikes are awaiting the opportunity for some testing and things are again looking promising in that regard.

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Re: CBX Racing

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Just received a set of tiny 13 mm iridium plugs for my NC30 from Japanplugs in France in under 2 weeks which is pretty good considering our postal service down here on the wild south coast consists of a runner with a forked stick (and the paucity of international flights during a pandemic).

I've now given up on my plans to go on a diet because after fitting a new spring to the GSXR rider sag is only 15 mm which is a bit too stiff. Static sag of 10 mm is OK and hopefully things will bed in with a track session and we might develop a bit more compliance. Still tossing up whether to enter the SA Historic Championship in a little over a month. Our track is still closed due to a quarantine breach in Adelaide and my hand is still very stiff and wooden but I won't be the first one armed racer. Altho' there is no way I could manage the CBX at the moment. It will have to be the NC30 if we run at all.

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Re: CBX Racing

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Warwick Biggs wrote:
Sun Nov 22, 2020 3:09 am
The CBX valve float issue was apparently addressed as follows (quoting Lionel Brancquart):-

"...we have worked a lot on the weight of the moving and rotating parts! we are 55gr lighter (tappet, valve +2mm tige de 4mm, retainer titanium Xceldyne, springPSI, twin cones, pellet) x24 parts all the parts have a surface treatment, the connecting rods are longer and lighter to accommodate piston in 66mm 2 segments and above all we have a very efficient ignition from Emanuel Guyonnet (who manufactures all the ignition for Guy Coulon Tech3)..."

I hope to have more detail to share on this remarkable CBX soon but invite comment on these details.
Here's the video for anyone who hasn't seen it?

https://m.youtube.com/watch?v=BYODFzLv3bY

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Re: CBX Racing

Post by Warwick Biggs »

it seems to me that even if you discount the calibration of the electronic tacho there is no doubting the incredibly light flywheel and how quickly the motor builds revs. I'm no CBX expert but it sounds like no other CBX that I've heard.

Do we have any other contenders for fastest revving CBX?

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Re: CBX Racing

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There's a bit of info about this bike concentrated in this thread.
Phil in Toronto
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Re: CBX Racing

Post by Warwick Biggs »

Well, despite the accumulated knowledge of the Skeptics I'm inclined to believe the makers' claims both for speed and weight. The weight is much easier to accept because I know that I could easily lose another 30 kgs from the lump if I had a healthy budget.

As for the motor, I'm not sure how long it might last or whether it would be a practical race engine but when you remember that for WSBK they are allowed 7 engines for 1 season and for the Island Classic they are allowed 7 engines just for the race weekend then I'm willing to accept it by those standards.

So... big drum roll... and as we have no other contenders I ...deep breath...declare the Brancquart CBX the world's fastest revving CBX. At least until we have another credible alternative. Oh yeah, gear driven cams...? There is heaps of room for either a stack of conventional gears or a rod and pinion set up in the existing cam chain space. But do you need to radically change the design or just use modern materials?

Until somebody else with lots of time and an equally strong emotional inspiration builds it, we won't know.

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Re: CBX Racing

Post by Rick Pope »

Somewhere on this forum is the documentation of a V-12 CBX with gear driven cams. It can be done......
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Re: CBX Racing

Post by Syscrush »

Rick Pope wrote:
Fri Nov 27, 2020 9:55 am
Somewhere on this forum is the documentation of a V-12 CBX with gear driven cams. It can be done......
Are you sure? I can't find anything about such a machine. Andreas' V12 uses 2 chains. Is there another V12 CBX somewhere?

You can see yourself in this album.

If I had unlimited resources, gear-driven cams would be my CBX vanity project.
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