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 »

By the way, a quick post script on my dragging brake problem. It was not bad enuf' to overheat the rotors so we carried on but a panel of experts conferred in my garage and concluded the problem was definitely in the calipers. Either it is crud build up or damaged rubbers as CBExtra posited as the cause. New stainless pistons, a bigger bore radial master cylinder and new seals are in the pipeline.

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Syscrush
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Re: CBX Racing

Post by Syscrush »

Another great report!

How was the cornering clearance on the X this weekend?

I'm very much looking forward to hearing how that new master works out for you. From a pure physics perspective, I don't get how the claims about them could be true, but so many people have responded so positively to them I'm sure that I'm missing something.
Phil in Toronto
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Warwick Biggs
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Re: CBX Racing

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Hi Phil, no problem with clearance but I was trying hard to hang off and stand the bike up.

I could not really relax and ride the Lump smoothly with much corner speed. It was more pick it up, point and squirt riding than racing. I need to tap the inlets on the motor side of the carbs so I can fit vacuum gauges to tune the low speed response off a closed throttle. The carbs are tuned for maximum power but need more work to make it useable power. Even the slightest throttle application off the bottom produces a violent surge that is hard to control when cranked over. It is also making gear changes ponderous and difficult - up or down.

The forum advice on radial brake mc's is unexpected so I guess I will just have to try it and see. Apart from ride days or away races I'm looking forward to a break from racing in order to work on these things. I'm also keen to reduce weight or at least move it around a bit. Mainly me. It always steers better and feels more stable when I'm virtually sitting on the tank.

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Re: CBX Racing

Post by bobcat »

I could not really relax and ride the Lump smoothly with much corner speed. It was more pick it up, point and squirt riding than racing. I need to tap the inlets on the motor side of the carbs so I can fit vacuum gauges to tune the low speed response off a closed throttle. The carbs are tuned for maximum power but need more work to make it useable power. Even the slightest throttle application off the bottom produces a violent surge that is hard to control when cranked over. It is also making gear changes ponderous and difficult - up or down.[/quote]

JMHO but I believe using a heavier crank, if not stock weight, would moderate the on/off, 2 stroke like
abruptness of the power and make it more rideable exiting corners. Restoring some flywheel effect will
also make shifting smoother. I doubt you would miss much straight away speed. I doubt that carb tuning
will yield what you are looking for. A less abrupt throttle pull (say half turn as opposed to quarter turn)
would also help. It sounds as though the motor makes plenty enough power to sacrifice a little to make
the bike rideable.
Bob
82 CBX, 81 CBX, CB1100F, 79/82 CB900F (avatar)

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Syscrush
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Re: CBX Racing

Post by Syscrush »

I'm sure you've thought about this, but maybe changing the cam on the throttle tube would help? These guys sell throttle systems with replaceable cams to help tune stuff like off-idle response:

https://www.g2ergo.com/product-category/street-bikes/

I have one of their throttles along with the "Jimmy Twister" outboard bearing and I like it a lot.
Phil in Toronto
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Re: CBX Racing

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I use a Venhill QA throttle with a choice of cams and yes, changing the cam may help. However, a crisp throttle off the bottom is what I really need. Tuning the NC30 with vacuum gauges markedly improved initial throttle response and I would expect the same improvement with the CBX. The crank is Honda Racing spec so I need to adapt and keep the revs in the power band. No going back.

I have bought a 16 mm Ducati S4 Brembo front brake master cylinder and will let you know how it works with the Prolink calipers once I have reconditioned them.

When I pulled the bike down for inspection after the races there was evidence of a fair bit of oil mist escaping from the catch bottle. The bottle itself contained nearly half a litre of oil. I am still using the stock breather hole and with the increased power there is obviously increased blow by and case pressure. So it looks like a second breather will be required to reduce pressure and contain oil loss. A threaded elbow with a hose barb will be fitted to the top of the blanking plate that covers the void where the alternator used to sit and a better vented catch bottle will be fitted.

Clearly I don't need to run a PCV for a race bike but the rules do require at least a 1 litre catch bottle. In the meantime I have made up a bottle within a bottle with a vent pipe to the tail to reduce pressure in the bottle itself.

I also plan to modify the seating position again. I have some solid shorter pegs coming and will further raise the seating position with more foam. Ideally I would like to move further forward but the tank restricts that so I'm also thinking of a shorter fuel tank with pingels on both sides. The existing LHS pingel is no good on tracks that run to the right because I have to carry excess fuel. I could plumb the rhs but a better designed alloy tank is the best solution. Maybe cut the bottom out and install a smaller alloy tank underneath but maintain the look? But that still restricts forward placement of the rider.

If anybody has any leads or ideas along these lines I'd be pleased to hear from you. So far all the fibreglass experts have declined my requests so aluminium would be my choice. Perhaps I could modify something off another bike with a central spine frame?

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Re: CBX Racing

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A 900 SS Ducati tank apparently has a similar shape on the bottom. I know somebody with a 900SS mould but he reckons it's too much work.

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Re: CBX Racing

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I have been talking to Rex Wolfenden about alloy tanks. Rex is half of the Melbourne based, brother partnership of TRex Racing which specialises in building CB1100R race replicas. His brother Clive does the frames and TIG work. Rex is around my vintage and was a long time Honda Oz race team mechanic. Their work is regularly seen on P5 grids around the country and features in earlier parts of this blog. If you have a lazy $100K lying around Rex might be convinced to build you one.

Rex currently has a CB1100R replica aluminium fuel tank for sale for AUD995.00. I know Roly used one on his Beast but with the necessary additional mods to fit my racer it is not an economic proposition and it is too large for my purposes anyway.

However, I have seen a CBX street bike wearing his highly polished alloy tank and it is stunning so for any ICOA members who are looking at dressing their machines up, Manx style, this may be an expense worth considering. If anybody is interested here is a link to the fuel tank listing:-
https://www.ebay.com.au/itm/125099611964
It will need a few minor mods but can be made to fit if you can afford it and it does polish up beautifully.

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Re: CBX Racing

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I hope to post a pic of Herman's CBX with the polished CB1100R tank soon. In the meantime I have been back on track for a ride day on the NC30. It was a last minute decision to go because the weather forecast was dismal for steady rain but it turned out to be sunny and dry until late in the afternoon when I arrived home and only then the heavens opened. Obviously the road race gods were in a smiling mood..

B4 that I had some really fun dices with the son of one of the blokes who sold me my first Norton Commando so it was interesting to reminisce with his old man who was spannering for his son and his grandson back in the pits. Have I ever mentioned that road racing is very much a family sport? Anyway, we cleared up some spurious old rumours about the death of one of our most talented riders of the mid 70's who was sponsored by his family's motorcycle dealership.

Carl Hammersley was killed on the public road on the eve of one of the big proddy bike endurance races of the time. These were really huge events by contemporary standards with thousands of entrants, big purses and large crowds usually supported by television coverage. Carl came to grief while running in the bike after a side stand flicked him off and into the armco lining the road. His death had further tragic consequences elsewhere in the paddock, while catapulting another up and coming rider to fame and a professional racer career. That racer Greg Pretty went on to an F750 Championship and established a highly successful jet charter business after retiring from racing.

Strangely and sadly, Greg was killed only a few years ago while riding his restored K1 Honda in the Adelaide Hills when he had a head-on collision with an Austrian tourist on a ZX10. The coroner found to our surprise that it was Greg who had been on the wrong side of the road, not the tourist who might have been forgiven for a lapse of concentration because they drive on the other side in Austria.

So to all those people who say road racing motorcycles is dangerous, I say, 'yes, but not as dangerous as riding on the public roads.'

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Re: CBX Racing

Post by EMS »

All stock CB1100R tanks were aluminum. Back in the day, there were quite a few replica 1100R tanks available. harris made one. You may find an old original for less than the AUD995.-. I sold an almost perfect CB1100RC tank about a year ago for U.S. $800.- I still have one, RD tank that I will keep for as a spare for my 83 R

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Re: CBX Racing

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I did a web search and the only genuine looking CB1100R fuel tank (discounting the obviously faux Indian ones) is the TRex. Harris no longer do tanks as far as I can ascertain EMS. Just looking at the Indian tanks suggests they will not fit and that their claims are suspect.

Just to follow up on my dragging front brake, I finally removed the David Silver front master cylinder and found the tiny return hole lurking underneath a tab bent back from the larger hole. I poked some stainless 0.5 mm wire thru' it quite easily so I don't think that was the problem. I have replaced the pistons and seals altho' the old ones did not look too bad and have spent most of my time attempting to adapt the Brembo master cylinder to a very crowded clip on. The DMR lanyard that I run and the air caps do not leave much room so some delicate grinding was called for. Hopefully, I will have it all back together and ready for testing fairly soon.

In the meantime I've managed to strip a stainless bullet head allen screw on the alternator cover plate. The other screws were tight and showed signs of very old loctite so I'm going to have to demonstrate some ingenuity to get the little bugger out. My easyout failed and with the bullet head there is nothing to grab hold of and not a lot of meat in the head. I am thinking of heating it with a soldering iron and seeing if I can hammer a slightly larger torx head into what remains of the screw head. I don't fancy trying to drill stainless out.

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Re: CBX Racing

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Well, heat and a torx head hammered in failed so I resorted to a fine chisel and even that failed so rather than butcher it any further myself, tomorrow I am taking it over to an engineer in Port MacDonnell. He mainly looks after all the alloy cray' boats over there. Short for crayfish because Port MacDonnell is known as the rock lobster capital of the Southern ocean.

When I was a kid we used to use cray meat as bait for fishing. Now they are daily flown out to Japan and China in private jets and fetch more than their weight in gold. But as bottom feeders they are incredibly high in heavy metals and micro plastics and can exceed world health standards. This is in one of the wildest and cleanest oceans in the world.

Port MacDonnell also had a long groyne and jetty behind which the cray fleet can safely ride out the gales that are blowing up from the Antarctic right now. This is also where my 'pit bitch' (a distasteful expression), photographer and muse Fran has threatened to take the Lump where she would push it off the end to create an artificial reef. She reckons I'm deluded trying to turn such a heavy road bike into a racer. I admit, it is a challenge with many set backs but as Roly says, "if it was easy, everybody would do it" which is a polite way of saying, 'its' a fool's errand'.

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Re: CBX Racing

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The latest minor modifications are an additional 20 mm alloy breather elbow tapped into the plate that covers the alternator void.
The existing breather is inadequate to cope with the higher crankcase pressure generated by the race motor. The positioning is partly determined by the need to avoid the rubber O ring machined into the back of the plate and avoiding the mainshaft as you can see from these pics..
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Re: CBX Racing

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And here is a pic of the Brembo front brake radial master cylinder. Locating the reservoir in a very crowded pat of the clip on was assisted with cable ties. Half my race bikes are held together with cable ties!

You can also see the lever guard (not very historic) but a safety feature for when somebody cuts across your bows hitting the brake lever and putting you on your backside, or worse, flat on your face.

The extra padding and profiling of the seat to move weight forward is visible as are the shorter rigid footpegs. On two separate occasions I've had spring loaded pegs knocked around after various impacts and I can assure you that it is hard to ride quickly when you lack a foothold. Solid pegs obviate a third occasion and shorter means less wear and tear on my boots. The Raasqs mounting plates have also been shortened to improve access to various parts tucked away behind them.

A lot of little things can make a big difference....

Next w/e's track day looks like it might be rained out so I may have to postpone testing for a while. Roly thinks my hesitation off a closed throttle is a needle issue. The CR Special carbs have 9 needle positions and multiple tapers so that simple statement covers a multitude of possibilities, all to be checked.
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Re: CBX Racing

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Why my pics keep being posted at 90 degrees is a mystery. Anyhow, racing is not all about the bike or the riding. At least half the battle is just getting onto the grid and that means meticulous preparation, a fair bit of organisation and a good dollop of cash. As a septuagenarian with a couple of relatively heavy race bikes (GSXR and CBX incidentally, both now have similar weights and power but in the case of the CBX at a much lower engine speed) and the need to easily load and unload them without assistance requires some of the aforesaid organisation.

In my case I have constructed a loading dock and skillion cover for my enclosed bike trailer as you can see from this pic. It is perfectly level and I have a Kaneg locking wheel chock that grips the bike when I roll it into the trailer. The shed incidentally I built myself in a few days for $400 from my builder's scrap heap. It requires 3 metre clearance so that I can lift the trailer roof up for loading. I noticed Fran hovering around the nearby parts of the garden while I worked on building it because I had to stand on the very top step of my tallest A frame ladder to tech screw the iron roof on and she was worried that I might fall off. So was I! The last time I fell off a ladder I knocked myself out cold and for a while I thought that was what had caused my stroke until we found it was actually a latent heart issue.

In any event there are many physical hazards from motorcycle racing apart from the obvious ones on the track.
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