CBX Racing

CBXs, new bikes, old bikes, cars, trucks, general chat, off topic, this is the place to post it.
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Syscrush
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Re: CBX Racing

Post by Syscrush »

Warwick Biggs wrote:As for synchronising 6 carbs I think they would have done it by eye/ear Phil.
What I'm saying is that I don't see any mechanism for adjusting sync in what we see of the throttle linkage in that photo.
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Re: CBX Racing

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You may not have noticed my temporary absence after I replaced my browser and then suffered the inevitable password problems, hopefully now remedied.

To respond to Phil's question about tuning the carbs - Seth says they set the slides by eye on the bench using the adjuster nuts in the pic. They are then basically tuned by changing the jets. Each cylinder apparently requires individual jetting so its a bit like a 2 stroke in this regard.

I have discovered yet another cause of my misfire. The bottom of the carb rubbers on 2 and 4 were split. This was not visible on the bike and only noticed with the head off in good light. Those cylinders would have been sucking more air than desirable.

I have also pulled the extended sump off to clean the pick up filter. It was not too bad and there were odd bits of neoprene, varnish and metal fragments but no evidence of the high temperature silicon gasket goo that I use. Earlier in this thread there was some debate about the pros and cons of silicon gasket goo and blocked filters but if you use modest amounts of high temperature goo it should not be a problem. I have used it to seal the cracks in my carb rubbers because a couple of new rubbers will cost around AUD$750. Ouch!

I'm making a few other mods to the motor while the head is off. When RPE did my cams Hugh was rather circumspect about the specs. Inspection reveals he took a short cut. Rather than build up the lobes to achieve more lift and duration he simply ground off the heel or baseline (the round base opposite the lobes) and then shimmed it up accordingly. Not the ideal way to achieve better gas flow altho' it works.

You can see from the pic below that the engine has been running too rich by the amount of carbon altho' it was quickly cleaned up with a nylon brush fitted to my rotary tool.
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Re: CBX Racing

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To go back to the heavy carbs I have modified the linkage on my CR Specials to achieve an almost straight pull on the actuating cam. They are rather roughly assembled from Keihin USA and the angles and layout need a bit of adjustment by putting the actuating cam in a vice and bending it this way and that to achieve a perfectly straight pull.

This has made them a bit lighter at the bars altho' they are still heavier than is desirable. Here is a pic showing the mechanism. A larger diameter pulley would solve the problem.
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Re: CBX Racing

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Jumping back to the pic of the head above you can also see that cylinder 4 has been sucking more air than the others.

Next, the valves will come out for inspection altho' they have passed the petrol pool test. If they are OK (they have occasionally kissed the piston crowns as a result of missed shifts) I will fit a new set of Kibblewhite springs, retainers and seals.

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Re: CBX Racing

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Great update - that's really good news about finding the issue with the rubbers.

Could that stand-off for the throttle cables bend under the forces it sees in use? Would there be any value in bracing it to help keep everything nicely aligned?
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Re: CBX Racing

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Quite possibly Phil. There is a lot of pressure on it. The other issue with the CR Specials and CBX packaging problems is that the carbs are almost down draft but the floats are designed to function on the level.

It has been suggested to me that making up a new manifold from alloy and then using ordinary freely available equal length rubbers would help both gas flow and level out the carbs. This would be a rather laborious mod, getting the angles right with a bit of tricky cutting and welding. It would also require re-designing the main jets/float bowls to make them shallower to keep the bottom of the carbs off the cases. As it is I have had to grind down the drain plug on one carb to stop it resting on the ridge in the cases that accommodates the primary drive chain.

Another possibility is fitting 6 Lectrons. Expensive but allowed under the rules. I would need to get one to see if they would fit better than the CR's. A third alternative is going back to my bored out CV's and removing the diaphragms. As I have pointed out in another thread, fitting CR Specials to CBX's is highly problematic.

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Re: CBX Racing

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I'm racing in the Classic next w/e on the NC30 so, yesterday I took the 750 out to a practice day and I had some fun playing with some young guns on their 1000cc superbikes. I get a ridiculously juvenile kick out of cleaning up the kids and their reactions when I take off my helmet to reveal a visage old enough to be their grandfather.
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Re: CBX Racing

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Just back from the track. This time with a sick NC30. It ran fine all through practice yesterday with a number of minor issues (including a grip that threatened to come off in my hand) fixed along the way.

Then in Q1 I was nearly taken out by somebody who threw their bike away right in front of me going in way too fast over the water tower. This was the exact same spot I crashed a few months ago and made me feel a bit nauseous. Then, a lap later my little jigger suddenly lost power. After pulling half the bike apart and doing basic diagnostics we were forced to retire what has been until now a very reliable bike. Suspicion is resting on the hard to diagnose spark unit that is apparently susceptible on the V4's.

Both my racers are now U/S and I''ve closed up the shed to focus on more productive endeavours for a while. Old bikes....!

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Re: CBX Racing

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Well, never overlook the obvious. Loss of power was caused by a power lead to the front coil coming loose. Once re-connected it ran fine except... Why is there always a qualification with race bikes? The radiator was almost dry. It was filled up and then lock wired b4 the race. Hmm, investigation with it running at normal temperature ruled out any obvious coolant leaks from either top or bottom radiator, the hoses or the motor. Plugs were all the right colour but a compression test showed it needed a de-coke and valve grind - all cylinders even at least at around 120 psi when they should be 160-213psi.

An air bubble into the catch tank every 10 seconds or so and the gradual discolouration of the pink coolant to oily brown suggested a more serious looming problem.

My diagnosis is a leaking head gasket, warped head or heads or cracks. Probably the former. Anyhow the heads will have to come off which is a problem because all my bench space is covered with CBX bits. I have another race coming up next month with the Easter Cup so will have to run the 750 Suzuki against the litre bikes where I'm sure to get lapped by the young guns. Maybe I should just concentrate on getting the CBX ready for the Seniors in May? Decisions, decisions.

Any other opinions on the coolant issue appreciated.

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Re: CBX Racing

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Things are now moving so fast and the world has turned upside down since my last post. A difficult debate is now underway as to whether my club should continue with the Easter Cup races against the advice of government health experts who are trying to limit the spread of Covid 19.

Racers being the rugged individualists that they are (I'm being polite) tend to take a rather cavalier attitude to all things official. My view is that we will all have more time to fiddle with our bikes in the shed. Perhaps we could start a CBX Covid Projects page? Is it just me or do other people think of the words of Edgar Allen Poe's raven whenever the word covid crops up?

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Re: CBX Racing

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Warwick Biggs wrote:Racers being the rugged individualists that they are (I'm being polite) tend to take a rather cavalier attitude to all things official.
I think if any of us imagined - really imagined - what it would be like to go into a tree at 150 miles per hour we would probably never get into the cars at all, none of us. So it has always seemed to me that to do something very dangerous requires a certain absence of imagination.

[/quote]My view is that we will all have more time to fiddle with our bikes in the shed. Perhaps we could start a CBX Covid Projects page?[/quote]
That sounds like a great idea!
Is it just me or do other people think of the words of Edgar Allen Poe's raven whenever the word covid crops up?
I'm pretty sure that one is just you. :D
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Re: CBX Racing

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Sorry Phil. Covid - corvid - raven - "Nevermore, nevermore', quoth the raven. No more racing for the foreseeable future is what I was thinking.

The club actually did the right thing and cancelled the races altho' we have a socially distanced working bee this w/e to plant trees. Worthy but not my favourite track pastime.

Meanwhile, on the CBX front the valves came out and thankfully were all straight and good once the carbon was removed altho' number 5 could not be lapped in properly and needed re-seating.

It was a pain getting Tims' extended sump back on after cleaning the pick up filter. It might have been easier to invert the bike but having 2 rubber O rings to keep in their seats while lining everything up for the 8 bolts to go in straight was not helped by a bit of gasket goo causing everything to slide around. I haven't put any oil in yet but I will be amazed if it seals. I reckon I will probably have to get some new O rings from Bill but we will see. Is Bill still shipping, I wonder?

Things look grim in the US but in South Australia there have been no new infections for nearly a week and only 6 deaths, all associated with travellers. Oz declared a pandemic well b4 the WHO and went into lockdown very early and has been doing a fair bit of testing and tracing which has made all the difference. Initially there was confusion between the Feds and the States as a result of our horse and buggy Constitution but an emergency 'national cabinet' was formed with the leaders of all levels of govt sitting round the table to informally overcome those systemic problems and has worked OK. Most of our cases are from cruise ships as it was the peak of the cruising season and they are floating petrie dishes.

Anyway this may allow us to get back to riding in the not too distant future altho' I don't see the borders being opened anytime soon. Maybe we can even think about racing b4 the end of the year???

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Re: CBX Racing

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We are still under restrictions in Oz but they vary State to State and we live 2 klms from the border between Victoria and South Australia. We have permits to cross for essential shopping but the cops are monitoring licence plates and questioning anybody doing more than a single trip per week which I had already done when I had a CBX 'non essential' errand to run.

I had to deliver Roly's 24 valve stem seals to the guy in Mount Gambier who had re-seated the no. 5 inlets. So I decided to take my road bike, one of the last oil head BMW R1200 ST SE's - a twin cam with ESA that hardly ever gets ridden. I even gave it a wash but that was a big mistake. All went without incident and on the way back I decided to explore a different route back thru' the riverside village of Donovans. It had some challenging corners and spectacular views over the Glenelg River.

But just as I neared the border not far from home the bloody thing just died on me. The fuel pump controller for the injection system sits in a dished aperture in the side of the tank on nearly all BM's and they accumulate water and eventually short. It is a well known design fault that the Gemans refuse to fix. I think it is a plot to keep their economy growing. At least that is MY conspiracy theory. They seem to be all the rage at the moment.

That reminds me of another story of an Oz BMW rider at the Isle of Man one year berating a crowd of German riders in a pub about the war because his BM had broken a mainshaft. Pure Monty Python. Back in Oz he was crippled after having a head on collision on a remote rural road with another bike being ridden by an off duty cop who was killed. Poor Chris seemed to have been born under a bad star but such is life....

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Re: CBX Racing

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Warwick Biggs wrote:
Fri May 01, 2020 8:51 pm
The fuel pump controller for the injection system sits in a dished aperture in the side of the tank on nearly all BM's and they accumulate water and eventually short. It is a well known design fault that the Gemans refuse to fix. I think it is a plot to keep their economy growing. At least that is MY conspiracy theory. They seem to be all the rage at the moment.
Rick, I suspect that's not the issue here, based upon the death of my own R1200 on the side of the road a few years back: BMW issued a recall on the fuel pump mounting flange, they were prone to cracking and the fuel would then leak and pool there and get into a small electronic module and short it out, bike dies. Then it evaporates and the bike starts and runs fine, for a while. Super fun failure mode, not.

There was a recall for this. Mine was replaced under warranty many years after the main warranty had expired - you might investigate that and see if that is the issue at hand.

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Re: CBX Racing

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Snap! I already had mine replaced under recall Nils together with the rear hub flange that could cause the rear wheel to part company.

These bikes are not as premium as their pricing suggests and the Germans are even more perverse about acknowledging faults than the Japanese but don't mention the war!

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