CBX Racing

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Re: CBX Racing

Postby Warwick Biggs » Wed Apr 24, 2019 9:57 pm

I weighed the lump with the new exhaust: 217kg with 10 litres of fuel and 5 litres of oil, distributed 103kg on the rear and 114kg on the front.

With a lighter crank CrMo frame and and Dymags it should be possible to get it well under 200kg whereupon I would have to stop calling it 'the lump'. Those mods are unfortunately outside my budget.
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Re: CBX Racing

Postby EMS » Thu Apr 25, 2019 5:21 pm

You picked some of the most expensive and radical areas to save weight. A lot of times, small things are overlooked. Your front fork brace can be of a lighter version, so can be the billet aluminum triangle engine hangers.
I bet there are quite a few areas where 200 grams here and there can be saved and it all adds up. Your seat arrangement may be nice to your butt, but weighs in on a scale....I would even consider looking at the tank.
The CB1100R had an aluminum tank..
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Re: CBX Racing

Postby Warwick Biggs » Thu Apr 25, 2019 11:08 pm

Heh EMS, I figure the easiest weight savings are with the supernumerary on top. I have lost 4 kilos just by cutting down on the grog. If I spend a bit more time running around on the tennis court I reckon I can get it down another 2-3 kgs. This is almost certainly the cheapest way to reduce weight. Every time I think of opening another bottle of champagne I think that is another half a hp handicap. It seems to work quite well.

As for the other bits you mention, I've already gone to a lighter seat, engine hangars and fork brace. Also, my original idea with this project was to keep it fairly stock with basic performance mods. That was the main reason I chose a CBX instead of a Bol Dor or Katana, both bikes I like and have owned in the dim dark past. Another area you didn't mention and often overlooked is the drive chain. My main focus has been on the handling where I think the real benefits are to be found. I do keep my eye out for cheap light weight wheels, crank and frame, however.

If anybody is aware of any of these items languishing somewhere, I'm always interested to investigate/negotiate.

Incidentally, I measured the mechanical trail with the rear shock set at 297 mm length and the forks (raked at 24 degrees) about 8 mms down in the clamps from stock. The trail is 108 mms. That is of course, a static measurement and I will see how this goes at the track tomorrow. I can drop the forks another 12 mms and raise the rear ride height a bit more than this, so we have a bit to experiment with. My guess at this time is that the steering will still be a bit slow and I will need to lift it a bit at the rear. We will see how the theory stacks up in practice.
R.
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Re: CBX Racing

Postby Warwick Biggs » Sat Apr 27, 2019 10:40 pm

Here is a rather poor pic (sorry Fran) of the new system fitted with the bike in action at the track during testing. Not surprisingly, when you make so many changes at once, we only got 2 laps in b4 having to pull in and bring it back to the workshop. Also, as I half expected the solderless nipple on the carb end was pushed off the throttle push cable resulting in the need for quick remediation at the end of the straight. While the carbs might snap shut under the springs alone when sitting in the pits, its' a very different story with 6 carbs wide open for an extended burst down the straight with the venturi effect of all that air being sucked into the motor. Because I was aware it could fail I was ready to temporarily hit the kill switch to bring it back under control but it was not a safe issue to try and ride around and I couldn't fix it at the track.

It was my mistake to think solderless nipples in the Venhill 888 Universal QA throttle kit would handle 6 very heavy CR Special carbs. That is why Honda fitted CV carbs to the CBX. Venhill have been kind enuf' to replace the entire kit free of charge and I will now get the nipples properly soldered.

Those 2 laps were still very useful in evaluating the other changes. Venhill provide 2 cams with their quick action throttle with the quickest fitted it is very quick indeed. Makes avoiding spinning the rear wheel quite tricky when loading it up the ramp into my trailer on the clutch but its' great on the track. The pic shows a bit more ground clearance with the suspension mods and it didn't want to flop into the corners so I think I can raise it further still. I didn't really get a chance to push it hard and we were nowhere near race pace so I can't be certain about how it will react at 10/10th's but its' still encouraging.

The matching intake manifolds and lighter weight also really made a noticeable difference, especially down the straight where it literally howled. Everybody at the track noticed the sound. There is still a slight hesitation coming off a closed throttle so I will try dropping the needles another notch t see if we can get a smoother pick up. At the moment its a bit like a light switch. Nothing much and then, BANG! It wants to spit me off, its' so keen to leap forward. Improvement still needed here but again, encouraging.

So a few things to work on b4 the race in a few weeks time.
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Re: CBX Racing

Postby Syscrush » Tue Apr 30, 2019 4:30 pm

That's a cool and encouraging update, Rick.
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Re: CBX Racing

Postby Warwick Biggs » Thu May 02, 2019 4:57 am

Thanks Phil. I've now had the offending nipples soldered and made some changes to the linkage so that the throttle is not so heavy and therefore less likely to cause trouble. I've also dropped the needles a notch and will play around with the ride height a bit b4 practice tomorrow week.

Carbs and throttle kit are now reinstalled and I'm becoming more adept at pulling them off and putting them back on. A bit of rubber grease and a confident push usually pops them home. Lowering the carb cam adjusters also makes it easier to get the cables around the rear engine hanger altho' I still have to slide the oil hoses around the bell mouths. Its' a delicate process.

Both bikes are now pretty much ready for the old farts on 11th-13th May. I'm a hopeful monster.

R.
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Re: CBX Racing

Postby Syscrush » Thu May 02, 2019 2:44 pm

Something I've been wondering about is how on earth Lionel Brancquart's CBX has any cornering clearance - given the issues you've had with the switch to 17" wheels, and the fact that that bike is running 16.5" wheels on forks that are well shorter than stock:

Image

How does that lean angle look to you, Rick? Is it compromised by the wheel and suspension changes?

Is that bike actually raced, or is it just a radical custom that turns some laps for fun?
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Re: CBX Racing

Postby EMS » Thu May 02, 2019 5:23 pm

He probably raised the motor in the frame, like Tom Marquardt did with his. :think:
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Re: CBX Racing

Postby Syscrush » Thu May 02, 2019 7:17 pm

Maybe, but to me it doesn't really look like it. I also thought that maybe they moved the steering stem down, but that also doesn't really look like it's been done:

Image

How does the relationship between the countershaft and swingarm pivot look in this pic?

Image
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Re: CBX Racing

Postby herdygerdy » Thu May 02, 2019 8:58 pm

Hi Warwick,

Don't know if you may have seen this post of mine some time back. With this method and a new gasket that can be re-used many times, it can be a goo-free installation, removing another risk of engine damage.

viewtopic.php?f=25&t=10537

As you can see from the posts, some like it, some don't. Each to their own & YMMV.

Keep up the great work and your very interesting posts, you write very nicely indeed Sir!

Cheers...Tony
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Re: CBX Racing

Postby Warwick Biggs » Fri May 03, 2019 9:18 am

First time I've seen that bike. The rider's stance suggests it might have some familiar limitations and its' obviously not set up for historic racing. Why not ask him? Does anybody have a contact address?

And no, I hadn't seen the rubber band trick. Looks ingenious. I install the rubber gasket into the channel with a generous amount of goo (I know, I know) the night b4 and let it set overnight b4 flipping it over and installation. I agree about removing the coils (and of course the worm drive for the tacho) and taking care not to over tighten the bolts.

Some years ago I had the good fortune to attend the Centenary TT at the Isle of Man, a place of pilgrimage for many motorcyclists. There was a re-enactment of the very first race next to the bronze age mound at St Johns. This mound is the traditional seat of the House of Keys, the government of the independent state of the Isle of Man. An island with its own distinct language, culture and currency and an outstanding enthusiasm for racing motorcycles on public roads. The machines in 1904, little more than motorised bicycles, could not climb the sweeping mountain course we know as Snaefell. So, it was a flat course to start with. It was an impressive display of the earliest beginnings of the sport of road racing. The Manx are very superstitious, despite their politically incorrect and somewhat dangerous flouting of modern safety conventions and they really value their traditions.

Little did I realise that 15 years later, almost to the day, I would discover that one of my favourite tracks, now my home track, Mac Park has an almost identical history. The only road race track in Oz and perhaps the world, to be fully owned by a motorcycle club; the Mount Gambier MCC hosted its first motorcycle race in the very same year as the IOM on a flat gently banked circuit. In 1904 Mount Gambier (named for the very young volcano on which it is perched) also boasted at least 3 motorcycle manufacturers, as well. The names Lewis, Cavendish and Birkfeldt are virtually unknown today but based upon what I have recently read (thanks Colin Thompson & Adrian) the experiences of those early riders would not be unfamiliar to modern riders. Perhaps more accidents involving stock but a similar dangerous predilection for going fast.

Thankfully, the MGMC also values its traditions including the Seniors or Old Farts races. Age may weary them but nothing much short of the final curtain can keep some mature age motorcycle racers from dragging their bikes out for a scratch. Don’t imagine this is some sort of quaint ritual. The bikes are blindingly fast and cataracts and agues are forgotten when the lights go out and the field takes off. Adrenalin and endorphins take over. The red mist descends and the race is on. You might think they are racing for sheep stations rather than a $2 trophy.

A week to go today…
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Re: CBX Racing

Postby Warwick Biggs » Fri May 03, 2019 8:00 pm

Looking at that bike again a number of things occur to me. Firstly, the 3 pics are all different, presumably different stages of development. Second, the rear swingarm is very different to a prolink with a completely different linkage. Third, those modern U/D forks are set very steep so I'm guessing it has non standard triple clamps to acheive a rideable trail. The sprocket to sprocket angle looks about right but it is a very long swing arm and the wheelbase looks like it could be problematic on a tight track.

Finally, if it is being raced as opposed to any other application, it must be competing against modern bikes where it is unlikely to be competitive but it looks good.

I would like to know more about this bike. Where is it? It also raises the question of how many serious CBX racers are out there in competition that I'm not aware of. At the moment I am aware of James Fisher in the UK, the Brints in the US, Roly if he puts his bikes back on the grid followed by me. Em tasol.
R.
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Re: CBX Racing

Postby Syscrush » Fri May 03, 2019 9:28 pm

Warwick Biggs wrote:Finally, if it is being raced as opposed to any other application, it must be competing against modern bikes where it is unlikely to be competitive but it looks good.

I would like to know more about this bike. Where is it? It also raises the question of how many serious CBX racers are out there in competition that I'm not aware of. At the moment I am aware of James Fisher in the UK, the Brints in the US, Roly if he puts his bikes back on the grid followed by me. Em tasol.
R.


I don't think it's actually raced, I think it's a promotional tool for the engine building service.

Some more info on the bike here.
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Re: CBX Racing

Postby Warwick Biggs » Sat May 04, 2019 8:02 pm

OK, 'long and low' was one of the polite comments by a French rider who focused on its tyre shedding ability. Not a racer. No armour plating or crash protection. Frame only modified at the rear to accept the K5 swingarm so yes Phil, it is a show piece for the engine. It may not even be capable of doing a race and even with a very steep front end and jacked rear, on 16.5's it will be scraping its cases just getting it out of the trailer.

There is a race tuner in Queensland (Lindsay Donait) who claims to have built a 165hp CBX race motor that he tried to sell me. These claims are hard to test and come with highly questionable reliability. Roly seems to have his motors running fairly reliably with 130hp. That is probably about the practical imit for the CBX unless you have buckets of dough. There are other air cooled tuners achieving bigger numbers but the motors at this level have a life measured in hours. They require big budgets to race and are hungry monsters. Nice to play with if you have the resources but not practical for a club racer like me.

Frankly, I would just like to see more CBX's on the track, with or without 80hp, more or less. The reality is they just aren't there for very good reasons. Even Roly has retired his demanding racers which is a pity because he was finally getting somewhere. Looking at my unlimited period 5 competition for the weekend, I see Katanas, XR69 replicas, Harris framed Bol Dors and Z1R's not to mention the gaggle of 350 TZ's. On a technical track like Mac Park where weight and agility are the pre-requisites for results, the CBX with me in the saddle will be doing well not to finish at the back somewhere. Even hotted up K1 Honda 4's can be faster.

To put this in context I can turn laps in the high 1'20's on the 400 but the best I've managed on the CBX is the low 1'30's and I need to knock 10 seconds off this to even think of winning. I'm working on it second by second but it is post stroke therapy for an age pensioner. Lets be frank... So, like the Brancquet machine, its' really a bit of a show piece. A genuine racer? I like to think so but still with the obvious impediments of bulk and weight. If it wasn't Japanese it would be better running in the BEARS against the likes of Jotas, Benellis and other like exotics. But it can be competitive with the careful setting up of a relatively stock machine on the high speed sweeping circuits like Phillip Island. It definitely surprises the skeptics and in the right hands it can win. And of course, it adds colour and particularly sound to the grid and is a hoot to punt to boot, particularly on a budget.
R.
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Re: CBX Racing

Postby EMS » Sun May 05, 2019 8:39 am

Warwick Biggs wrote: a 165hp CBX race motor that he tried to sell me. These claims are hard to test and come with highly questionable reliability. Roly seems to have his motors running fairly reliably with 130hp. That is probably about the practical imit for the CBX unless you have buckets of dough. There are other air cooled tuners achieving bigger numbers but the motors at this level have a life measured in hours. They require big budgets to race and are hungry monsters. Nice to play with if you have the resources but not practical for a club racer like me.

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