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 »

I know this is not really CBX related but here is a pic of young Declan Carberry after scoring his first ever podium.

Looking like he has just stepped off the set of Lord of the Rings, the 16 year old displayed maturity and skill beyond his years. His 600 was obliterated by the thousands down the straight but in atrocious conditions he just picked them off under brakes and with superior corner speed to beat top internationals and works and MotoGP racers and score a close 2nd to winner of the Master of Mac Park, Arthur Sissis.

Sadly, given the increasing role of big $ in securing premier class rides, it is unlikely that the lad from Mount Gambier will ever get to live out a dream to race at that level. But if he does crack it via ASBK and WSBK you saw him here at ICOA first.
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Re: CBX Racing

Post by Warwick Biggs »

Can somebody with technical skill put this pic correct way up please?

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Syscrush
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Re: CBX Racing

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Warwick Biggs wrote:
Mon Oct 04, 2021 9:03 pm
Can somebody with technical skill put this pic correct way up please?
It really looks like it is correct, but that the forum software is rendering the preview image incorrectly.
Phil in Toronto
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Pics of Perry, my '79.

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Re: CBX Racing

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I took it with my phone if that makes any difference.

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Re: CBX Racing

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I've had the NC30 up on the stand doing some minor work. After lubricating the cables I had to strip everything to get at the carbs buried in the V of the motor to lubricate all the linkages. Hopefully, this will eliminate any more sticking throttle problems. I have also taken the opportunity to fit braided brake lines as the original rubber ones were swelling under pressure and reducing feel under heavy braking. Hopefully this will shorten my braking distances.

I've placed some rubber spacers under the seat to give me an additional inch of leg room. I had to put them at the back because the front of the seat slides under the frame so this produces a rather steeply sloping seat forcing me further forward. I chose this method rather than building up the top of the seat because I need to be able to slide across the seat smoothly and extra layers of rubber on top will reduce my movement. More leg room means that I can better use my legs to weight the foot pegs and also improves gear changes.

I'm just waiting on a 42 tooth rear sprocket coming from Tyga in Thailand to give me a bit more jump out of the corners altho' I'll lose a bit of top speed down the straight. I have dropped the countershaft sprocket from 15 to 14 to run 14/40 at Mac Park but it is not enuf' in the slower corners where I lose too much time. By way of comparison 15/40 is Phillip Island gearing.

I try to avoid first gear in the 6 speed box because of the risk of finding neutral while trail braking towards the apex. Not a good place to lose power because a 2 wheeled bike needs power to remain stable. When the power is removed the geometry changes radically and you risk crashing. Ideally you should always gently power thru' the apex, altho' you can use a bit of rear brake to fine tune your speed - exactly as you would if you were turning a long wheelbase big bike in a tight 'U' turn. Just doing it at speed. You balance it on the throttle and rear brake. People who say they never use the rear brake on their sport bikes are not doing it right.

The thing with these high revving 400's is that you have to ride them like 2 strokes and keep the revs above 9K at all times. The V4 is not as bad as the across the frame fours because it has a bit more torque but you still need to ring it's neck to maintain forward progress.

The next event is a ride day next w/e followed by the State Historic Championships at the end of December. I expect Roly to be working on the new motor for the CBX around then after State border COVID restrictions ease when vaccination rates exceed 80% of over 12 year olds, so have again entered the NC30 in the Period 6 Senior class.

Here are a couple of pics from the MP Classic earlier this year. Sorry about the photographer, Pierre's watermarks but he is a CBX owner so won't mind me sharing them with you. Note the one coming over the water tower. If you look closely you will see that I had a TRex right up my clacker. We are on identical lines so he is almost hidden from view but was just millimeters off my back wheel.
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Re: CBX Racing

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And another one showing the cornering clearance of the crank end caps. I've raised it significantly since then to give me much improved lean angles for more corner speed.
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Re: CBX Racing

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Warwick Biggs wrote:
Fri Oct 15, 2021 12:14 am
If you look closely you will see that I had a TRex right up my clacker. We are on identical lines so he is almost hidden from view but was just millimeters off my back wheel.
Holy smokes - that photo is unbelievable. I went back and looked at it multiple times before seeing the other rider. It looks like he's not even casting a shadow - are you sure he's not a vampire?

Maybe bring garlic to the next meet - just in case.
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Re: CBX Racing

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Yes Phil, I think he was after my blood because he had to wait 3/4's of a lap until the straight to get past, using all the 150hp in his CB1100R replica to do it.

Maybe the garlic would help convince complacent South Australians to maintain their social distance? Trying to get them to obey the health rules takes all of my humour. Riders briefings are turning into tedious lectures about wot not to do.

Just a few minutes ago I came out of the workshop after doing a bit of house keeping and thinking the CBX is looking a bit sad under it's sheet but the white board says it all - "awaiting the race motor". As I walked out I was speculating on replacing my GSXR track bike with an R3 Yamaha. I suspect the smaller bike would be better for improving my corner speed than a super sport as well as being a hell of a lot cheaper to run? Tyres are the killer costing $4-500 per session. I should buy shares in Metzler and Bridgestone.

On that front we picked up an NC30 race bike that has been neglected for 4 years for just $1K after a fellow approached me with an offer at the last race meeting. It runs when you pour fuel directly into the carbs and looks good with full race glass. It will go off to have the tank and carbs cleaned up and sorted by a guy in Bendigo who just loves tinkering with race bikes. Then it will be given to a promising rider in the club. There are a few 'keen as mustard' contenders who have demonstrated a commitment to the sport that outlasts girlfiends, football and all the less desirable distractions that plague adolescents. This is how I think clubs should run and it demonstrates esprit de corps as well as making racing affordable for deserving youngsters.

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Re: CBX Racing

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I'm pleased to report I knocked 3 full seconds off my PB with the aforementioned changes to the NC30. The day started ominously when 10 minutes from home it started pissing down with rain. Pushing the gods, I'd determinedly left the wets in the workshop. Oh well, at least I'd found an airbox in my shipping container full of bits for Rob's $1K NC30 race bike so I could give it to him. A few bits were missing from it but what can you expect for a grand?

Catching up with all the familiar faces and by the time the slicks were up to temperature the sun was shining and the track was drying. I missed the first session because it was still wet enuf' to kick up spray but there were not a lot of people so sessions were long (15 laps) but there were only 2. Superbikes and the rest. So there was no rest for the wicked. And the sun shone and it started to get hot on the track and off. Temperature went up and times down.

Most satisfyingly, I felt like I was driving thru the corners well. Braking later with real feel coming back from the braided lines gave me time and confidence to set up the corners the way I like then throw the thing on it's ear and power thru' in a single smooth arc. My best time of a 1'26 was definitely a club class race winning time but subject to the caveat that in a race you rarely get clean uncluttered laps as you try to deal with all the traffic. Still I was very happy with the improvement in testing after my rather disappointing race last time out.

I don't know how long an air freighter takes from Bangkok at the moment but my 42 tooth rear sprocket should help me a bit more when it arrives hopefully b4 the SA championships at the end of December. The only snag on the race horizon at the moment is; Roly has to deal with a wonky knee so there could be a delay with the race motor for the CBX. As Oz opens up after COVID there are predictions that elective surgery will suffer as the wards fill up with anti-vaxxers and clog up the hospitals. The Oz Medical Assocn (all the doctors) have suggested anti vaxxers should not be allowed into the public system but I suspect that would be a step too far for our pollies. Dipsticks Rule! But thankfully, not at the track.

Anyhow, as I get to grips with how to ride this track on a smaller bike I'll be quicker on the CBX. It handles and brakes well and what power it has I can use so the only question is whether I take the risk of having it laid up in Roly's workshop seeking more grunt or just put that off and run it as it is???? The National Championships are at the beginning of April so I'll take a raincheck on that but the CBX is entered. Rain, hail or shine, we''ll be there.

Whaddaya reckon?

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Re: CBX Racing

Post by steve murdoch icoa #5322 »

I admire the fact that you can swap between a CBX and the NC30.
The differences in power delivery and physical dimensions must be huge.

I change riding boots and it can throw me off. lol.

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Re: CBX Racing

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I know what you mean Steve and seriously, finding a good pair of modern racing boots is a problem because they all feel like clown's shoes to me. You have so little feel and you may as well go out in clogs. Give me traditional all leather rubber soled boots without all the plastic and lurid colours any day but you can no longer get them, for love nor money. My Alpinestars seem to be the best of a bad lot.

Practising with the modern 300 SS class is a lot of fun and I credit it with getting some of my old feel for the front end back and improving my septagenarian cornering speed. This is the feeder class for domestic superbike racing as well as MotoGP with all the young and not so young hotshots. The improvements translate more easily to the historics and bigger bikes than you might imagine. Feel and confidence are pretty much the same thing.

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Re: CBX Racing

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Steve, taking up your point about the difference between a light flickable bike like the NC30 and a heavy behemoth like the CBX there are of course big differences in theory. Putting aside the fact that the CBX makes more than twice as much power and torque the main difference is weight and the point of inertia.

The worst and most restrictive problem with the CBX in terms of handling apart from weight is ground clearance but b4 we even get to rectifying that problem, there is the problem of grip, or lack of it. The skinny old fashioned CBX wheels limit grip. So the first thing to fix is the wheels. All the best and stickiest tyres strong enuf' to handle the CBX weight are in 17" rim diameter. Conti Race Attacks are the best of the 18" tyres for the CBX but there is bugger all in 19".

So, smaller diameter wheels are the first step but mean a drop in ground clearance which means even shallower possible lean angles and slower corner speeds. What you pick up in grip from better tyres you give away in loss of ground clearance. Also the stock swingarm on the Prolink limits your rear tyre width to a 165 when a 180 would be ideal and give more lateral grip. The fore and aft grip remains the same so this is in fact only of marginal difference with a mildly tuned motor.

So then you have to lift the bike up. Luckily the front forks are quite long and there is enuf length to work with. The rear Prolink shock is primitive and can be replaced with a modern quality adjustable shock with springs front and rear to suit weight. In my case that is 11 or 12kg units to handle my weight of between 85-88kg. The stock forks need to be re-valved at this point. Then experimenting with adjustable rear dogbones at the rear will give you the perfect compromise between ride height and swing arm angle that should be around 12-13 degrees. Get this wrong and you risk power application lifting the rear and the worst kind of high-side accelerating out of a corner.

Assuming all that is fixed you now have reasonable levels of grip, adequate ground clearance and stable geometry. Notice we haven't touched the frame? There is no need to; it is perfectly adequate for racing. The first models had inadequate forks and brakes but the Prolink remedied these deficiencies. A front fork brace helps but that is it. You don't even need a steering damper if your frame is straight. You then work backwards with the front end, dropping the forks until you can quickly change direction without losing too much clearance and while watching the effects on the rear end geometry and finally you set the sag front and rear and you will have a CBX that can really handle like a race bike.

The final issue left to deal with is the inertia so just simple weight reduction can get the wet weight down to around 200kg from more than 265 stock. If you can afford Dymags and lots of titanium and carbon fibre you can go a lot further but we are talking basic stuff you can do on a budget to improve the CBX handling. You could write a book on dieting a CBX and its not surprising that dieting is such a big industry. You should probably start with the rider.

Now you are still going to have a big bike with more inertia so how do you ride it differently to the lighter bike? Well, its basically the same but your apexes and lines change a bit. Where you might apex the lighter bike at 12 o'clock the CBX might be at 11 o'clock. The critical thing tho' is where you come out of the corner. Ideally within an inch or 2 of the outside of the track and the best way of maintaining maximum corner speed is to maintain a single clean arc so that when you put the bike on it's side it stays on the same angle all the way around without drifting or playing with the steering. In this regard where you look is where you go and you have to have enuf' control to put it in exactly the same position lap after lap - to be perfect, in other words. That is the aspiration in any event

The heavier bike will involve a bit more leverage picking it up for example in a quick change of direction but even that can be improved with ride height adjustments. It is simple leverage physics. In MotoGP they now have electronic ride height adjusters so they can be adjusted for each corner. The big six has a little commented upon advantage over across the frame fours. The wider engine (with most of that width up high) gives you the same sort of leverage that a tight rope walker has with the long balance rod that he carries. That helps a lot in minor changes of direction.

So you see there is not a lot of difference in principle between riding the NC30 and a well set up CBX. I have just compressed what has taken me 6 years of trial and error to work out on how to get a Prolink to handle like a race bike should. Of course, when I fit a more powerful engine I will probably have to make more changes to the rear end and fit a wider swing arm for more rubber so things never stay the same for long on a racer. Development is constant.

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Re: CBX Racing

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When I said I hadn't touched the frame that was a bit of a fib because I did cut the headstock and pull it back 4 degrees. That speeds up the steering of the Prolink and raises it at the front by a smidgin. If you used the Mark I frame with Prolink front and rear parts you would not even need to do this.

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Re: CBX Racing

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I've just fitted a larger alloy sprocket to the NC30 to give me 14/42 gearing. Having done that I now suspect a 41 tooth rear might have been better. I will find out next time I go to the track.

The Elf inspired single sided swingarm is both good and bad. Good because I can change rear wheels in 2 minutes flat and the sprocket pops off without having to remove the rear wheel. Bad in that the notched wheel that operates the chain adjuster is crude, difficult to access without a special tool and ends up mangled from using drifts to turn it. You need to lift the back of the bike without using a paddock stand (ie: a sling and block and tackle) to turn the thing and because its greasy a large C spanner just slips off. Grrr!

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Re: CBX Racing

Post by Syscrush »

Warwick Biggs wrote:
Wed Oct 27, 2021 6:54 pm
If you used the Mark I frame with Prolink front and rear parts you would not even need to do this.
Are you claiming that the twin-shock and prolink bikes have different head angles?
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