CBX Racing

[Warwick Biggs]

So it turned out that the NC30 carbs were well out of sync. Not that it makes much difference up top when the throttle is wide open but it does affect the initial pick up so it should improve the first third of the throttle response and help coming out of corners.

Roly has sent thru' some pics of the CBX motor going back together. You can see that the rods are numbered because they have been balanced with the piston and crank. You can also see the rods are H pattern and they are full chromalloy for additional strength.

There does appear to be some outer cam shaft wear that will need attention b4 long. I'm not sure how to tackle that other than new cams and if they have to be replaced I wonder if I can get lighter ones? When I compare the CBX cams with the NC30 cams they look very agricultural and heavy. This accords with my theory that the weight of the valve gear is the CBX's Achilles heel restricting engine speed.

[Warwick Biggs]

As a matter of interest to tuners the manufacturer of the CrMo rods, VEP Racing certify them as safe up to and over 800 hp for turbo applications so they should be able to handle a modestly tuned naturally aspirated engine with a relatively low 10.3:1 compression ratio.

[Syscrush]

I wonder if I can get lighter ones? When I compare the CBX cams with the NC30 cams they look very agricultural and heavy.

Is gun-drilling the OEM cams an option?

[bobcat]

As a matter of interest to tuners the manufacturer of the CrMo rods, VEP Racing certify them as safe up to and over 800 hp for turbo applications so they should be able to handle a modestly tuned naturally aspirated engine with a relatively low 10.3:1 compression ratio.

Same rods ?

[Warwick Biggs]

The rods do look to be the same. Have you used them? As for 'gun drilling', I am not aware of that process Phil altho' I can imagine. I know Webb use some exotic metals and welding techniques with their camshaft work. They also have master copies of most cam profiles and could presumably make up a lighter and better wearing set of cams. This is something I plan to discuss with Roly shortly. He has struck a few other issues too so we will see.

Quite a bit going on at the moment. There have been a significant number of withdrawals from the Championships due to extreme flooding in the Eastern States (following huge catastrophic bushfires the year b4) with many large towns and cities inundated. We are hearing stories of classic race bikes destroyed with thousands of houses unlivable. Covid numbers are also on the rise again too with the economic impact of fuel prices, lockdowns and escalating inflation hitting many competitors pretty hard.

Then there is the mad Vlad war in Europe allied with an increasingly assertive China now deploying war ships close to Oz in the Solomon Islands. It makes our racing seem fairly trivial by comparison. A case of Nero fiddling while Rome burns perhaps? Are we again on the brink of a global catastrophe of our own making?

[Warwick Biggs]

Just a teaser from today's qualifying for the National Championships.

I was 6 seconds a lap slower in the first session than the last time I raced the Lump a little over a year ago, despite having 20% more power. Every time I changed down I was locking the back wheel because of the higher compression motor. By the second session I was starting to adjust and concentrate on my lines.

Given that I haven't had time to focus on set up or come to grips with the very different dynamics, I have to expect to start somewhere near the back of the grid but hopefully, as the races progress, so shall we.

[Syscrush]

Very exciting - good luck out there!

[Warwick Biggs]

Lack of preparation time and a host of problems contributed to a frustrating series of races all won by the 160 hp Irving Vincent in lap record times - https://www.irvingvincent.com/motorcycles. Altho' electronic fuel injection is banned in P5 this thoroughly re-engineered modern iteration of the HRD somehow skirts the rules with a mechanical system. I ended up getting lapped by the mono-ing monster. Even more indignities were inflicted by being consistently beaten by a Ducati and a Guzzi, the latter ridden by a novice.

My old foot peg problems returned due to ground impacts causing the rhs to swivel down so my foot kept slipping off. So I had to ride with my heel on the stub. Very hard to turn the bike or move around like that. I need to buy a decent set of solid race pegs and scrap the period Raasq rear sets. Spring loaded pegs really have no place on a race bike.

Then I had to spend a day making up new rear brake bracketry after my thoroughly original CBX master cylinder decided to micturate brake fluid everywhere. I could not find seals in time so I cannibalised a wrecked bike just to get it past scrutineering. Ratio was all wrong and the piston was not perfectly aligned but it worked - sort of. Enuf' for the scrutineers anyway. I had to make up new mounts with a scrap of alloy and a hacksaw and then 3 hours were wasted trying to bleed the damned thing. I also suspect the brake fluid wrecked the bushes in the pro-link arm because the rear end was flapping around like a chook on the run from the cook. That manifested itself most in the sweeping double apex coming onto the back straight forcing me to back off going thru' and then on the exit.

Then I kept hitting the crank end caps in the tight corners because I was riding it too much like the NC30. I actually went OK on the little jigger with a couple of PB's but against a very fast field of TZ's, RG500's, etc. I was out-classed but not embarrassed. However, my real focus was the CBX where I only managed one lap within a second of my previous best time and it was horrible, almost un-rideable. The carburation was mush off the bottom and the motor seemed sluggish to pick up revs altho' it had great power where I could open it up and wind it out on the straights. But coming out of the slower corners it was woefully fluffy and in the corners I kept slamming the cases on the ground and then running wide. Overall a terrible disappointment. Roly thinks I should be happy to have finished all the races and not come last but I had much higher expectations.

Now I need to get back into the workshop and strip, reconfigure and reassemble everything and then do some development tuning at the track b4 the Seniors races in May.

[Warwick Biggs]

I should have credited journalist Fran Thompson for the photos - thanks Fran. Thanks also due to my team of covid marshals for doing a difficult job at an event where the public were keen to forget all about the virus

[NobleHops]

Rick, pardon me chiming in, but is there a track you can get some seat time in at? You seem to be testing your setup at the races. That said, I deeply admire your derring-do

[Syscrush]

160 hp out of that Vincent is mind-blowing.

Sorry you didn't get the results you want. I'd be proud just to have those photos, but that's why you're out there racing and I'm sitting here reading about it.

Thanks for sharing.

[Warwick Biggs]

Hi Nils, chime all you like. The Mount Gambier Motorcycle Club owned road race circuit that hosted the Nationals, Mac Park is only a pleasant 25 minute rural drive from my home and if need be I can organise private access for testing. However, as we have regular monthly track days and other events it is not necessary to grab the keys just for my exclusive use.

It was unfortunate that Roly had other commitments that meant the build of my race motor was delayed until the week b4 the National Championships. That lack of preparation also extended to my not having ridden the Lump for around a year. Meanwhile, I had been steadily improving on the NC30 which could hardly be more of a contrast to ride. Most importantly, with the NC30 I can carry much higher corner speed without risk of scraping due to lack of ground clearance. Trying to ride the Lump the same way is counterproductive.

Prior to the meeting I thought I had the Lump handling relatively well without scraping and I'm still trying to figure out why I had such terrible handling problems. There was a compounding of issues that all fed into the results and that make it difficult to isolate any one thing. If forced to nominate one issue above the others it would be my old bug bear of ground clearance, or lack thereof. I was also frustrated and angry with my inability to make use of the extra power because of poor fueling in the first third of the throttle. I'm guessing this is a slow jet issue and that is where I will be looking first when I pull the carbs off for inspection.

I did eventually get the Lump down to just a second or so off my previous best (when I had 20% less power) altho' that was still 4 seconds a lap slower than my times on the little NC30 that has less than 40% of the power of the CBX. It is great to have the HP but HP does not alone win races. Even the fire cracker Vincent had a top professional racer in the saddle and it would be disrespectful to my competitors not to acknowledge their skill levels.

Fundamentally, I have to accept that as a nearly 70 year old pensioner still recovering from a stroke and with very limited mechanical ability, it is a significant challenge for me to convert the CBX, a heavy road bike, into a racer that can compete with the best . The Vincent arrived in a huge pantechnicon containing a full workshop with a team of mechanics, engineers and electronics experts and is clearly a multi million dollar showcase for a large engineering company. That is not an excuse but a necessary reminder to keep things in perspective.

[Warwick Biggs]

Just a quick explanation of why ground clearance is so difficult a problem on the CBX. It starts with going from a 19/18"" wheels to 17" wheels for the best race tyres. The relatively long CBX forks can be dropped in the triple clamps but this requires the rear to be lifted. This can be done with different length custom made dog bones for the rear shock. However, there are limits because as you extend the shock it can foul the linkage. Working around that problem has you coming up against another - being the increase in the swingarm angle and the effect that has on the chain drive and finally the handling. Increasing the S/A angle beyond 12 degrees can cause the pogoing I experienced and can reduce rear wheel traction due to the forces pulling on the drive chain. It is a fine compromise to find the sweet spot.

[daves79x]

Are those Kerker headers? They would drag in stock configuration. Curious as to what you think brake fluid did to your Pro-Link swingarm ?

Dave

[Warwick Biggs]

No Dave, the headers are Delkevic.

Nor is the Lump stock configuration. The head stock has been cut and shut to pull it back to around 24 degrees. The forks have been significantly dropped in the clamps and have modified springing and damping. The rear wilbers is significantly longer than the original air shock and since it was fitted I have further lengthened it with a variety of custom dog bones. Sag has been set and I run around 15 psi in the forks. The swingarm has been widened a smidgin with an angle grinder in order to fit a 165 x 17 battlax slick on a ZZR 5" rim. Front is a 120 x 17 on a Honda VTR1000 rim.

I'm thinking of trying a Pirelli slick on the front as it has a higher 70 profile altho' it is probably about the same diameter as the others when cranked over. Every mm helps. Does anybody know?

Roly reckons that a swing arm angle of over 11 degrees will cause a CBX to pogo. Mine is now set at the max at around 12 degrees.

My musing about the brake fluid was that being a rather caustic oil it could adversely affect the bushes. I have the bike up on the stand at the moment with the rear suspended by block and tackle and the weight off the suspension. I cannot detect any play in the bushes. And I have now acquired a pressure bleeder. I do not want to spend hours trying to bleed a partially 'dry' system again.

I will install a kit in the original master cylinder as the jury rigged cylinder I set up at the track is useless apart from getting it past scrutineering. After that the CR Specials will come off to inspect and clean the slow jets. Then it will be back to the track for testing. I may have to think about going back to 18" wheels.