CBX Racing

CBXs, new bikes, old bikes, cars, trucks, general chat, off topic, this is the place to post it.
Post Reply
Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Today I finally arranged an avgas source in an attempt to deal with the 'varnish' from crappy unleaded fuel blocking the slow jets leading to a stumble or misfire at initial throttle opening.

However, it seems to have led me into another 'issue' because I had to go thru' the local aero club. That turned out to be a bit of a distraction as I ran the gauntlet of enthusiastic aviators and their range of quite sophisticated and fast ultralight aircraft with an assortment of interesting engines to inspect. Motorcyclists are of course suckers for light aircraft so that ended with an offer of 2 free non flying aircraft from which I might make one good one - for nothing. Just remove them from the hangar please. O Oh! When I told Fran she held her hands over her ears and started humming...

User avatar
Jeff Bennetts
Posting God
Posting God
Posts: 2408
Joined: Wed Mar 05, 2003 8:38 am
Location: Ohio, USA
Location: Ohio, USA

Re: CBX Racing

Post by Jeff Bennetts »

Listen to Fran!

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Hopefully readers of this blog all survived the recent festivities and are looking forward to a healthy and happy new year.

As I write this I am nursing injuries sustained in the South Australian Championships as a result of an over ambitious passing lunge that brought down another rider and punted the Lump and moi off into the outfield where we did a bit of scrambling b4 dumping it in a sand trap. That will be another $1,000 helmet heading for the greenhouse. The crash was entirely my own fault altho' in my defence there was a gaping hole in heavy traffic on the inside line of the very fast double apex corner which is a personal favorite. I almost made it but a rider on the outside on a fixed trajectory just clipped my rear wheel taking his front out and shooting me off the track like a booster rocket.

Luckily there were no serious injuries altho' the Lump ingested some sand into it's bellmouths b4 I managed to hit the kill switch. I have it up on the stand and will strip it for investigation and replacement of broken bits. I had started fairly well getting a good second row starting position on both bikes during qualifying in large mixed fields but things began to deteriorate from there. Clutch problems with both bikes hindered starts and bits started falling off. I lost a lever protector. Then a footpeg came loose on the NC30 and finally, in 35 degree heat (over 60 on track) I had fuel vaporisation issues. They cleared once we got some air moving around the motor but in 5 lap races (dashes), a good start is imperative.

Our injuries were piffling in comparison with Levy Day who returned over the northern winter from his Championship winning in Europe and almost immediately trashed one of Ruwoldt's (Southern Classic winning) Harris Kawasakis after the brake fluid boiled. Recovering from a broken right side collarbone sustained at Brands Hatch he now has a broken left collarbone to match. That happened on the first lap of one of my first P5 races and thereafter the attrition rate from crashes continued with lots of DNF's, especially with the touchy 2 strokes in the heat. One rider even got hit in the face under heavy braking by a fork spring after the top circlip in his TR750 let go.

Turn 1 is a very tight, heavily banked hairpin where the TZ's and lighter bikes have an advantage in negotiating the elbow and fairing bashing as 20 or 30 bikes jostle for space. So, after avoiding the worst of that I usually start picking off the slower bikes but inevitably the leaders have cleared off. So it went. I was consistently beaten by #61 (the big blue and white Suzuki from last month's battles), despite being a second a lap faster and then finishing within 100ths of a second of each other with me on his back wheel over the line. It was frustrating and emphasised the importance of a good start, altho' I did manage to consistently beat one of the podium getters at Broadford and set some very fast times on the Lump. Overall, good fast racing with lots of overtalking battles and great fun.

1'27 at Mac Park is a respectable time for a modern 600 supersport and as fast as I have managed on the Lump in the past. the heavier fork oil and extra shims definitely helped with ground clearance altho' I still managed to hit the crank end caps a handful of times which does limit my confidence a bit. But for the first time I was faster on the big 6 than the NC30 on which I was consistently lapping around 1'28. Hopefully, you can see from the pics that I'm standing the CBX up and hanging off more altho' that technique remains a work in progress (more work required! Bum right off the saddle and knee and foot tucked in, not sticking out, is the goal).

Now I will have to start '23 by stripping and cleaning the carbs and fixing whatever else needs fixing in readiness for my next Classic races in March.
You do not have the required permissions to view the files attached to this post.

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Here is a pick of the heavily chamfered crank end cap. This practice is not recommended as each time it touches down it pushes the bike wide and when you are racing to the outside lines (to the track limits) the only place you can go is off. More adjustments to the suspension are required.

And here is Marc Crighton on his Suzuki. He rides like a motorcycle cop but is nevertheless surprisingly fast and the bike, an immaculate and powerful missile.
You do not have the required permissions to view the files attached to this post.

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Stop Press: Roly Skate has declared that me trying to race the Lump is "flogging a dead horse". Many may agree. EMS, I hear you nodding. It is hardly a racer, considering it's weight and girth. But it is fun to ride and in my defence, I blame him for inspiring me to try with his outrageous 'Beast' and 'Beastess'. His criticism boils down to my efforts to gain ground clearance without major modifications to the frame al`a Tom Marcquardt.

Well, that would be fine if anybody had bothered to help me with those frame mods that demonstrably worked. But sadly, that has been a well kept secret and it has been difficult to even gain a general description of those mods, much less any details. Fair enuf', I suppose if we were competitors but Roly refuses to wheel out his racers to compete. My photos of his bikes are not detailed enuf'!

So, I will keep titling at my windmills (apropos considering the effect of wind turbines on the world's bird populations). I have now jacked up the lump at the rear to the max of over 40 mm and will experiment with springs at the front and fork positions. One possibility that it is hard to assess; is the extent to which the Lump flexes laterally at full lean which may mean no amount of lifting will cure the tendency to scrape the cases and it is up to me to ride around the problem.

I am also quite proud of the rear brake stay arm that I fashioned out of billet aluminium to replace the stock steel unit, thereby saving 250 grams or a ham sandwich. Plus, it looks good with all the drill holes. Now, is this Spondon creation an answer to my 17" wheels framing issues?:-

https://grabcad.com/library/spondon-cbx-frame-1#! And, if it could be, is it period?

PHOBMAN
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 5
Joined: Sun Jan 01, 2012 8:47 pm
Location: TEMECULA CA. USA

Re: CBX Racing

Post by PHOBMAN »

I have just found this thread, and it reminds me of my '79 CBX that I entered in the Castrol 6 hour at Manfield New Zealand. Riders Bob Neilson and Mel Wrigley. We had heard that the CBX's were disintegrating after missing gears in the Aussie 6 hour so we made special shims and shimmed the gearbox. The Factory teams blew the bikes motors, but we finished the race a respectable tenth, and I went on to do two Circumnavigations of the North Island and a circumnavigation of the South island of New Zealand with tent and Girlfriend on the back!

steve murdoch icoa #5322
ICOA Member
ICOA Member
Posts: 4069
Joined: Tue Mar 04, 2003 9:12 am
Location: St. Catharines, On. Canada
Location: St. Catharines, On. Canada

Re: CBX Racing

Post by steve murdoch icoa #5322 »

Rick, no doubt you have seen these pics that Jeff posted of Dr. Tom's bike?
http://www.cbxclub.com/forum/viewtopic.php?f=24&t=12209

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

No, I hadn't thanks Steve. The mods are a lot more radical than I imagined and not so easy to replicate. They are also for the twin shock. the Mark 1 version did not change the swingarm pivot and mainly relied on cutting an inch out of the rear down tubes thereby raising the lower part of the motor and effectively moving it forward slightly. The Mark II version for Roly was a lot more complicated with changes to the swingarm pivot as well as extensive mods to the frame. Well beyond my ability, that is for sure. Marquart's description of the mods as "eyeball engineering" suggests a fairly relaxed approach to chassis design.

Your NZ 6 Hour experience sounded great, Phobman. The thing about production racing in the 70's was that you could ride your bike to the track, unbolt the lights and road gear, race and then ride home. That was how many competitors did it and provided you didn't crash, it was a fairly cheap sport. How things have changed. Pukekohe Raceway is about to close to bikes (to make way for nags) and they are holding one last endurance event very shortly. Quite a few Oz competitors are crossing the ditch to compete for sentimental reasons. Of course, the Kiwis reckon they invented just about everything in motorcycle racing. They certainly punch above their weight.

My reference above to Spondon's CBX frame was made in ignorance of what actually happened to Spondon. Like Trident, another British engineering firm that made many of the XR69 replicas floating about, Spondon are no longer in business. However, I had no idea of Spondon's connection with Stuart Garner. He misused Spondon as the stalking horse to purchase the Norton name and raise very large sums of cash that ended up completely destroying a well-respected engineering business as well as leaving Norton a smoking ruin and it's workers pension fund cleaned out.

The story of how a former gamekeeper with little credit and no motorcycle expertise pulled off a huge fraud, conned thousands of motorcycle enthusiasts with a sentimental dream, was convicted of fraud and then basically walked away with a suspended sentence, using the bankruptcy laws to avoid all the judgements against him and leaving a long trail of destroyed lives behind him would make a fantastic movie. In fact it is an indictment of the British legal system, the ridiculous power of branding and the vulnerability of the system (particularly, it seems British motorcycle engineers).

The Norton brand survives under TVS ownership and may still have a bright future but it's troubled recent past must stand as a sad and cautionary tale for the British motorcycle industry as well as CBX racers looking for a race frame.

Rick Pope
ICOA Rally Director
ICOA Rally Director
Posts: 2270
Joined: Wed Sep 03, 2003 3:16 pm
Location: Lawrencburg, IN
Location: Lawrenceburg, Indiana

Re: CBX Racing

Post by Rick Pope »

<<Marquart's description of the mods as "eyeball engineering" suggests a fairly relaxed approach to chassis design.>>

More likely, it's in reference to his being an optometrist.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

I see, said the blind man.

But Rick, I reckon with all those changes, bits cut out here and there and other bits heated and bent it would be tricky to replicate them side to side, much less bike to bike. For example, there is no detail as to exactly where you cut 26 mm from each rear frame tube. Cutting it higher will move the motor differently to cutting it lower. Maybe he took it out of the middle and it was mainly trial and error but how many frames would you go thru' that way?

When you compare it to modern Computrak precision as used by many race teams, it looks "relaxed". But it works. Just, not for me. By the way, does anybody know what the total weight of the Prolink frame is? I have never seen it quoted anywhere.

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

I'm guessing it is over 20 kgs. Heavy, by any standard, at any rate and does it flex laterally? I would say so. How much is a moot point but when the bike is cranked over to the max there is very little compliance in the suspension and it is the bending of the chassis that absorbs most of the bumps and irregularities in the track.

It is this dynamic that makes me wonder about the effectiveness of my relatively piffling efforts to increase the ride height and prevent the cases scraping. I am down to the last few mms in any further raising of the bike but it may be completely ineffective if the bike is bending like a banana laterally at full lean under the weight of that lump of a motor (plus the lump on top). Of course, the lump up top is the weight that can be moved around to stand the bike up more and that has to be our main focus.

In any event, I have fitted the 29 mm Racetech fork springs and lifted it a further few mms at the back and will be testing at the track next weekend. We will see, but the supposedly stiffer springs (according to Racetech) don't feel that way in the workshop so I am skeptical about the accuracy of their online table of comparative spring specifications. I have marked the position of the cable tie on the fork leg so it will be easy to tell when I stomp hard on the brakes. I'm also hoping the 3 mm narrower than stock Racetech springs don't distort and bend or bind in the legs. That could be really problematic and I'm really hoping it hasn't made things much worse.

It's always a bit nerve wracking returning to the track after a crash; so many things to sort out and my back is still sore just to remind me that one of my favorite fast corners has bitten me. :handgestures-fingerscrossed:

EMS
ICOA Member
ICOA Member
Posts: 10151
Joined: Wed Mar 05, 2003 7:55 am
Location: North East OH, ICOA 3904

Re: CBX Racing

Post by EMS »

Warwick; You may be surprised. Several years ago, we had a project with a Harris frame and we did a comparison of frame weights. The 79 CBX bare frame weighed in at 16.1kg. The Prolink frame is marginally heavier as it has basically only two additional brace bars, one on each side under the battery compartment. So, let's say 17kg.
The flex of the CBX frame is greatly exaggerated by many people, but it is actually not the frame, but other suspension parts that caused the heavy criticism of bad handling of the early CBX: The spindly 35mm forks and the swingarm and its poor pivot mount. Both areas were addressed by Honda in the 1980 model and further improved with the Prolinks. Yes, the frame itself has some flex and you can demonstrate and measure this on a bare frame by sticking a rod through the steering neck and another one through the swingarm mount and then twist both bars against each other.
But...!!! The frame has the engine as a structural member by design and this is what makes the difference. Any frame bracing on a CBX frame is a waste of time and a non-scientific, "shade tree mechanic" effort. With the engine in the frame, there is more bracing between the entry points of actual force from riding than anybody could ever do. Compared to a modern bike aluminum box frame, the CBX is still a poor handling bike, but we are talking about 40= years of engineering advancements and the general drawback of a steel trellis frame. And the world was always in awe about what Ducati was able to do with their trellis frames in their Superbikes, when the 916 ran circles around the competition. If you decide to race a classic bike like the CBX, you should not look with envy at the handling prowess of modern 600cc racers or even a contemporary bike that was much smaller and derived from production racers. It all boils down to what I said in the very beginning: The CBX was never designed for racing and no matter how much you try to improve it, it will always be what you call a "lump".

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Yes, EMS but the late 70's early 80's was the great era of 'production racing', leading to the development of the CB1100R Honda's first purpose built proddy racer. Everything you say is correct but you have to remember that I am racing against 'improved' production bikes of the era like the Harris, Trident and Moto Martin. All souped up air cooled production bikes. It behoves me therefore to 'improve' the CBX for competition with it's peers.

The amazing thing is that many of the improved proddy racers were just as fast if not faster than purpose built racers of the era like the TZ750's TR750's and H2R's - in the right hands, I should add. I know the Lump can compete with these bikes because I have been doing it for a while now. It is also no wider than a CB750 and there are some very quick tricked up Honda 4's racing without scraping their cases.

If I were starting again I would have stuck with 18" wheels. Georges Martin said as much ages ago when he was still making CBX historic racers but I wanted a wider choice of rubber and erroneously thought I could do it on the cheap by emulating Roly. So I missed that boat. I may still reverse direction on that.

I have now discovered some pin hole leaks in my tank that has me thinking about fabricating an alloy tank for the CBX. I will post something under the appropriate heading to see how many owners may be interested in replacing their steel tanks that will all be rusting, with alloy. If there is enuf' interest we may be able to convince a fabricator to do a run.

Warwick Biggs
Amazing Poster
Amazing Poster
Posts: 952
Joined: Tue Nov 03, 2015 9:23 pm
Location: Australia
Location: Australia

Re: CBX Racing

Post by Warwick Biggs »

Here are a couple of pics by a pro from last month's Championship that have cropped up on the web.

Poor Dave #17 who is normally faster than me on his P6 CB400R found to his disappointment that his newly acquired P4 CB750 was slower than his 500 despite the extra hp and he struggled to keep up with the NC30. I suggested he ditch the Avons on it and try Contis that can handle the weight better. The old adage that HP is no good unless you can use it comes to mind. I'm hoping to find some pics of my crash because it all happened so fast that I can't be sure exactly what happened beyond my hair brained idea to pass 3 bikes in one corner.

The pic of the Lump is not so interesting other than it shows how high I have lifted it to try to keep the cases off the deck and also that I could have a smaller, more steeply shaped slab sided tank rising from the edge of the seat more like the alloy Harris race tanks or old TZ tanks. That would also simplify fabrication issues caused by the 34 mm backbone and reduce costs. My fabricator (who is cutting the rust out of the seam of my tank and whom I'd asked about replicating it); as soon as he saw the graceful lines of the CBX tank he just shook his head and said, "nnooooo!"

The pic of Levy Day on Rob Ruwoldt's green Harris Kawasaki was taken just b4 he crashed it and broke his collarbone (again!). An occupational hazard for professional road racers. I believe the bike is also a mess so that is Simon Cook's TRex CB1100R and a Harris Kwacka destroyed in consecutive meetings. Not to mention the Lup finishing up in the sand trap. At this rate all the P5 racers will shortly be extinct. Luckily the CBX is built like a tank and less fragile than the race replicas. It is also worth mentioning that now that the Harris brothers have sold their business to Kawasaki it will become harder to get parts. They have stopped making tanks and a question mark hangs over their frame kits for the old air-cooled superbikes.
You do not have the required permissions to view the files attached to this post.

User avatar
Syscrush
ICOA Member
ICOA Member
Posts: 1714
Joined: Fri Sep 14, 2012 2:29 pm
Location: Toronto, ON
Location: Toronto, ON

Re: CBX Racing

Post by Syscrush »

Warwick Biggs wrote:
Thu Dec 15, 2022 1:10 am
O Oh! When I told Fran she held her hands over her ears and started humming...
I'm pretty sure that there's nothing in life more expensive than a free airplane. :lol: :lol: :lol:
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

Post Reply

Return to “Daily Discussion: By, For & About CBXers”