CBX Racing

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

Post by Warwick Biggs »

Time to post something. Went out for a club ride day and spent half the time trying to start the CBX. Eventually, after pulling the bike half apart, draining the carbs etc. I tracked down some electrical connectors that had been parted by the crash but being still taped were only intermittently connecting. Then I had to dry the plugs and recharge the batteries from all tha attempts to start, I'd well and truly flooded the thing and flattened the batteries. I warmed the tyres in the lunch break and eventually got out.

Sure does feel different with the new Rickman style solo seat. Much higher and further back seating means more leg room to move about which is good. But I came in with aching wrists because of all my weight being thrown further forward. This also affected the steering and over the bumps I had trouble trying to avoid the shock being transmitted by me into the steering. I also developed big dark blue bruises on my inner thighs from attempting to hang off the unpadded edges of the seat. So, we need to fix that.

And as a result I've changed the fixtures to make the seat much quicker on/off with less parts and I've modified it so I can get the tank off without removing the seat too.

The gearing was fine and it showed a good turn of speed. Good enuf' to surprise some of the contemporary race bikes and I do love how it can be squirted up the shorter straights where most riders button off a bit. That big 6 torque is addictive.

So now I'm fiddling around with small things. The 6 CR carbs are very heavy without the vacuum assist of the CV's. This can make for heavy handedness when you want fine throttle control to feather a slide or when transitioning on corner exit. My crash at the Island exiting Siberia is an example of what can happen if you give it too much too early. I've lengthened the throttle return spring a bit but my $10 MX throttle tube is a bit sticky so I've decided to order a Venhill 888 universal quick action throttle kit. It is not easy to lengthen the carb actuating arm and improve the leverage because it is curved (ie. engineered) and the geometry defeats my mathematically challenged and somewhat diminished mental abilities. Any suggestions gratefully accepted.

In changing to a 19 tooth countershaft sprocket (requiring some mods to the case protector finger) I'm also changing the final drive to a 520 chain and looking for a set of new rear alloy sprockets. Can't gt them in Oz so if anybody knows where I can get a 38 and 39 toother with Kawasaki ZZR600 hub centre and bolt pattern, I would be grateful. Next race might be Broadford later in the month. Enuf' for now...

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FalldownPhil
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Re: CBX Racing

Post by FalldownPhil »

Sorry it is in the USA but this is the place :-)
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Syscrush
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Re: CBX Racing

Post by Syscrush »

I have a G2 throttle, they sell a variety of cams to tune throttle response, and the Jimmy Twister outboard bearing makes really nice actuation.
Phil in Toronto
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Warwick Biggs
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Re: CBX Racing

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Ta too much. Noted.

In the mean time I got onto Vortex for the alloy sprockets but the heavy throttle issue is more to do with the 6 CR's than the tube. The G2 looks more like a quicker 1/4 street throttle tube rather than a 1/3 turn race throttle.

I've stretched the return spring a bit to reduce spring pressure but it is not clear from Keihin whether it is possible to lubricate the steel tube that runs thru' the 6 carbs that actuates the slides and needles. It looks like it is sealed on each side of the carby with neoprene caps and I don't want to spray it with lube until I know it won't affect the rubber/neoprene or I could make it worse if the rubber swells. I have some lanolin based spray and some brake pad grease but not sure what to use because not sure of its material. Also, I can't extend the lever on top of the carbs that attaches to the cables because it is a curved cam and too tricky.

Any ideas? I might try Bill Brint.

R.

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Re: CBX Racing

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Nope. Bill has the same problem as does everyone with Cr's fitted, I imagine. Now I'm trying Keihin but will they respond? The Japanese factories are not always the most communicative people when it comes to anything out of the ordinary. We will see.

R.

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Re: CBX Racing

Post by CBXTRA6 »

<<The Japanese factories are not always the most communicative people when it comes to anything out of the ordinary.>>

Hi Roland,
Very true !
May be Kazu could help you in the communication with Keihin?
JP

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Re: CBX Racing

Post by Warwick Biggs »

Well JP, I'm not Roland, altho' we are well acquainted and I'm not sure about Kazu, either but I'll try anything to lighten the throttle on a set of 6 CR's. Roland thinks they are merely 4+2 and therefore not really engineered for 6. Bill's comments tend to support this view. Keihin are probably not even be aware of the CBX community or this configuration of their hardware but we will see.

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Re: CBX Racing

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Warwick Biggs wrote:The G2 looks more like a quicker 1/4 street throttle tube rather than a 1/3 turn race throttle.
I'm not trying to push the G2 on you, but want to be clear what it is - they sell a variety of cams with different profiles to let you tune effort vs. actuation speed - and they have some with non-linear profiles.

I was the first CBX with one, and they worked with me to figure out a reasonable fitment - including throwing in an extra cam for free in case the one I asked for didn't fit or work as I expected.

I agree that the major issue is that you're working against 50% more return spring than what the carb designers had in mind. Reducing friction in the actuation could mean that it's a bit easier to make throttle adjustments, but more effort to hold it WFO. I think there's no magic solution for this.
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Re: CBX Racing

Post by cbxmel »

I know Jeff Coker of the UK cbx club has been running CR's on his 1233cc big bore special for a number of years. After initial problems I believe he has them set up ok now. Mel#1876 :auto-sportbike: :flags-wavegreatbritain: :flags-usa: :flags-canada: :flags-australia:
Bikes since 1960,BMW R27,Calthorpe 350 twin port, 50cc Maserati,C110,S90,CB92,CB77 webco 350 racekit,C72,CB450,TS125,GT380,GT750x2,Harley 45,Ariel Sq4,Vincent Rapide,NorVin shadow,GPZ750turbo,GSXR1100H,FJ1100,RC30,Moto-Martin cbx x4,CBX specials x3,79cbx x 20 & GL1500

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Re: CBX Racing

Post by CBXTRA6 »

Warwick Biggs wrote:Well JP, I'm not Roland, altho' we are well acquainted and I'm not sure about Kazu, either but I'll try anything to lighten the throttle on a set of 6 CR's. Roland thinks they are merely 4+2 and therefore not really engineered for 6. Bill's comments tend to support this view. Keihin are probably not even be aware of the CBX community or this configuration of their hardware but we will see.
Sorry for the name confusion ! :oops:
JP

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Re: CBX Racing

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Well, as I said, I'll try anything if it will lighten the throttle. The Venhill 888 appeals because it is a complete race kit with Teflon lined custom cables and I've tried it on a VFR400 where it is feather light. But I haven't ordered it yet in case there is something better. It's not cheap, either.

And Mel, its not a fuelling issue. It is the physical effort in lifting 6 slides against 7 springs. Logic suggests improved leverage is the answer but the cable attachment is not easy to modify.

Considering the number of CBX's out there running CR's I'm surprised the CBX brains trust hasn't yet come up with a fix.

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Re: CBX Racing

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Well Cronk me Voddy! Keihin has deigned to reply altho' not the Nipponese part - the US part (hold the horses, America is Great Again).

I am advised that Keihin only make one size throttle wheel (that is what the cable actuator is apparently called) altho' its hard to find on any parts list.

So it seems that the only solution is to fabricate a larger diameter throttle wheel myself (and make my fortune selling it to you's all). I'll see if I can find my old Spirograph set and next time I pull the carbs off I will try disassembling the linkage and up-scaling it. In the meantime, I've given up on waiting for a smarter solution and ordered the Venhill throttle kit.

Next race will be at Broadford on September 13th - the Hartwell Seniors. Between 'the lump' and myself our ages combined, we qualify for the 100 plus club (class) , a dubious honour, to say the least. Before then, I will be modifying the cases to accommodate a 19 tooth counter shaft sprocket. Roly will help me with that as he pioneered the method. It won't make much difference at Broaford but should give an extra 20kph trap speed at Phillip Island and a wider choice of gearing. I am currently at the limit with a 37 tooth rear and can't go any smaller there, all a consequence of the 17" wheel conversion - the butterfly effect.

Meanwhile here is one of my pics of a gent who checked out recently. He was pretty good on 2 wheels and 4. Is he, a) sick of hearing the latest fix for Norton valves or b) reacting to the mention of the names Dragoni and Ferrari or c) protecting the remnants of his hearing from Ago revving his MV next to him? (Answer in next post).
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Re: CBX Racing

Post by cbxmel »

The great man himself. John Surtees. Only ever met him twice when he was presenting the awards at Guildford Police HQ for road safety. Also his classic meeting at Brands Hatch in 1989.
A true gentleman. A disgrace he never received a knighthood when others less worth one did.
Mel #1876 :auto-sportbike: :flags-wavegreatbritain: :flags-usa: :flags-canada: :flags-australia:
Bikes since 1960,BMW R27,Calthorpe 350 twin port, 50cc Maserati,C110,S90,CB92,CB77 webco 350 racekit,C72,CB450,TS125,GT380,GT750x2,Harley 45,Ariel Sq4,Vincent Rapide,NorVin shadow,GPZ750turbo,GSXR1100H,FJ1100,RC30,Moto-Martin cbx x4,CBX specials x3,79cbx x 20 & GL1500

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Re: CBX Racing

Post by Warwick Biggs »

Correct and the answer is c). Ago pulled up next to him and just opened that MV up. Of course Surtees had a bit of a cantankerous reputation after he quit Ferrari after a fight with Ferrari team manager Sig Dragoni - something both he and Enzo later had cause to regret as it almost certainly cost them both another World title. That rap was probably undeserved. As you say Mel, he was a true sportsman and still racing bikes to the end.

Here is my favourite pic of Giacco. I took both this pics at the 2007 Centenarary TT.
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Re: CBX Racing

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Amazing photos, thanks for sharing!
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

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