Racing 2021

Fast Eddie said:

That sounds pretty conclusive !

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I am with Ralph too....there may be a pattern here....

Wasn't one of the issues at Pembrey a wheel bearing falling apart?

1, Question if that is really fixed now, proper fit of bearing in the hub and not spinning and bearings tightened properly on the correct width inner spacer?
2, Ask yourself why that bearing failed, because I have a feeling it could happen again if you didn't fix the source of the failure (hammering from a bad brake?).
3, Brakes, brakes, brakes....
4, Brakes 'and' damping/springing?
5, Another Pembrey issue if I recall was the rear shocks falling apart, and what caused that? You probably looked around the rear end for the source of that, maybe even just blamed the shocks, but they could have been getting a hammering from the front end under changing loads from....braking! And, is the damping (and springing) adequate under braking? Or is the brake induced judder compounded with floppy forks, and...even wheel balance!

You might say, ah but, I changed the shocks, and it didn't happen at Cadwell, indeed, but the loads generated at different circuits can vary, for example you don't brake at the end of a straight for a 1st gear hairpin at Cadwell like you do at Pembrey. And contrary to impressions, Cadwell is technical, and you don't load things that hard at Cadwell, until you run under 2 minutes, ask Ralph.

I know, teaching granny and eggs, but.....

storm42 said:

.....................The last race for me was another class win but much slower as the motor was detonating badly so I was unable to give it the beans. It had been getting worse over the weekend and was down to not having any Avgas to mix with the VPower fuel, I started off with a tank of the 50/50 mix but after the first race I added 2 litres of VPower therefor diluting the mix. I really didn't think it would make much differance as the Avgas is 100 octane and the VPower is supposed to be 99 octane, this I now do not believe.

The bike is one of the last factory RGBs and the frame number is No.1 so the potential for loosing a lot of money was high. Why do we do this to ourselves?

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I noted you were running slower and guessed you were just planning to finish and get your 25 class points....take it while you can....I got a nice set of pots for winning the class at the 2017 Race of the Year at Brands.

Avgas? Really only 100 Octane? Not really is it, although refered to as 101, when mixed 50/50 with 99 pump fuel it has still been tested as well over the normal ACU National regulation limit of 102, and it has lead in it!!

Of course....you could have bought some Classic Fuel Solutions 105 Octane as they were at Cadwell on Saturday! And, isn't there a high Octane pump in the paddock any more?

I don't have either of these options, and I am looking at adding Tetraboost to my pump fuel and have just contacted the French supplier (he is a Brit of course).

I don't run a very high compression, so as much as anything this is to get a bit of lead in there for easier plug readings.

I need some education about this RGB500 water cooled two stroke...... I had imagined at first you were talking about a Gary Bryans RGB Weslake!

Are we talking RG500 Suzuki related?

That was it, the points may be important if George Rustling starts doing all the races he is entered for.

I don't know about the octane of the avgas but it is sold to me from a tank marked 100LL, what I do know is, I haven't heard that engine pinking before and as the aviation folks seem to keep a close eye on what goes on, I figured the VPower was lower than advertised, or possibly with some of the dodgy practices that go on these days maybe not even VPower in the pump.

I think you have to order the classic fuel before the race so didn't consider them, that and the price, £75 + vat for 25 ltr

It was a bit of a shock just how bad it was in the last race to be honest, I will just add the experience to my other comedy of errors and move on I think. I think I will carry some Tetraboost from now on just in case.

SteveA said:

I am with Ralph too....there may be a pattern here....

Wasn't one of the issues at Pembrey a wheel bearing falling apart?

1, Question if that is really fixed now, proper fit of bearing in the hub and not spinning and bearings tightened properly on the correct width inner spacer?
2, Ask yourself why that bearing failed, because I have a feeling it could happen again if you didn't fix the source of the failure (hammering from a bad brake?).
3, Brakes, brakes, brakes....
4, Brakes 'and' damping/springing?
5, Another Pembrey issue if I recall was the rear shocks falling apart, and what caused that? You probably looked around the rear end for the source of that, maybe even just blamed the shocks, but they could have been getting a hammering from the front end under changing loads from....braking! And, is the damping (and springing) adequate under braking? Or is the brake induced judder compounded with floppy forks, and...even wheel balance!

You might say, ah but, I changed the shocks, and it didn't happen at Cadwell, indeed, but the loads generated at different circuits can vary, for example you don't brake at the end of a straight for a 1st gear hairpin at Cadwell like you do at Pembrey. And contrary to impressions, Cadwell is technical, and you don't load things that hard at Cadwell, until you run under 2 minutes, ask Ralph.

I know, teaching granny and eggs, but.....

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The wheel bearing was caused by a previous installation. A mild steel tube had been used as a bearing spacer, centralised in the hub by oversize washers. It was over long, so when the second bearing was tapped in the tube rode over the inner race and pressed against the race, leading to wear and nastiness. I replaced both bearings, made up a thick walled slightly undersized alloy spacer. Wheel spins freely.
The disc rotors are new (and expensive). Still need checking as Ralf suggested. I am not sure of the make of pad as I did not put them in. I should have done a proper check of head races, I did pull and push when the wheel was off, nothing noticeable, will revisit. New tyre, balanced wheel. Static sag 3.25 inches. Normal sag 2.5 inches which is about right I think.
Update on shocks, when I had them off I checked chain tightness through full swing arm movement, it got tight!! I set it, so now on the rear stand chain looks like my KTM, but feel back end much improved. This actually might have been one of the causes or contributory factors of the failure?!
Forks are basic Maxtons internals, just rebound adjustments. The previous owner was about my weight (I think) so I am assuming that spring and compression set for him so should be fairly close for me. Will get them looked at, unless another blindingly obvious cause shows itself.
Time wise I was chasing 2 mins, best was 2.02.

Ralph, I’m running 11.5:1 in my 920 and it normally just runs on pump super unleaded (although I put some booster in for track days).

So, unless you’re running some crazy CR, you should be fine on that stuff.

So, you must have either got dodgy / old / stale fuel… or sumthin’ wrong somewhere…

Steves said:

The previous owner was about my weight (I think) so I am assuming that spring and compression set for him so should be fairly close for me. Will get them looked at, unless another blindingly obvious cause shows itself.

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Spring rate wise, rider and bike weight and distribution are clearly factors. A taller or shorter person of the same weight may put the weight in different places. As will riding style, including how you like to apply and release the brakes. If you are not naturally very smooth on to and off of the brakes try to focus on that.

I would trust Maxton to deliver a good base setting, most of the time, but never a previous owner! And....never assume!

Nor should you trust something more because it is new! And if you didn't put the pads in, who did? When? Bin them if you don't know what they are.

I had a Suzuki disc that was like a clutch diaphragm or Bellville washer when I took it off! Lots of funny effects under braking, but mainly lots of lever travel on initial application as the disc had pushed the pads back.

Does sound like the brakes are an issue somewhere. What wheel hub and brake is it? And if there are two, dump one. I am guessing you checked the spoke tightness and run out including radial run out!

Do remember that the steering head bearings can also be too tight, and that gives weird symptoms as you unconsciously try to compensate with excessive steering inputs.

And whilst you are still setting it up, don't drop the fork yokes too far, that can give issues too, come back to a neutral setting before trying anything radical.

If you have a steering damper, take it off until the base problems are resolved.

Fast Eddie said:

Ralph, I’m running 11.5:1 in my 920 and it normally just runs on pump super unleaded (although I put some booster in for track days).

So, unless you’re running some crazy CR, you should be fine on that stuff.

So, you must have either got dodgy / old / stale fuel… or sumthin’ wrong somewhere…

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It was fine until hot and wide open throttle, and as it was worse with each dilution I am fairly sure it is the fuel. If on closer inspection I cannot find anything else wrong then I will leave well alone until Donington and there I will be back on my 50/50 mix.

Mulling it over I can say the bike on the straights and on the curves handles really well, it feels balanced , no sensation of wanting to run wide or tuck in. It goes where I look. It feels sensitive in slow corners with power off but I think that would be the case with most bikes as it becomes more about your sense of balance less about bike dynamics.
I set the brakes at my braking point to start the weight transfer, then progressively increase braking to max. This being where the problem starts, so logically the two areas of suspicion are brakes and the suspension at full compression. I have had this happen before on a CBR600RR, I changed the rotors to Brembo, I also revalved the forks. It was night and day, if I remember correctly the cause was the rotors. So I am leaning toward a brake problem which is a bit annoying as the discs are new!

I have a question, is Avgas thinner than say Shell VPower with all its cleaning additives, ie less viscous?

storm42 said:

I have a question, is Avgas thinner than say Shell VPower with all its cleaning additives, ie less viscous?

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I sort of feel you are really asking....did changing the mix ratio affect the jetting? Well it does anyway, because you are changing the oxygen ratio by reducing the Avgas.

That is part of what race fuels are about, not just detonation.

Clearly you have not had cause to question the quality of pump fuel before, so clearly any issues don't show at 50/50. A lot of tuners use nothing else but 50/50 mix. Avgas costs because of the lower volume it sells in compared to pump petrol, and because it is regulated for aviation use, which means more testing of the product as actually delivered to airfields.

Stick to a successful formula, i.e. 50/50 if you can get Avgas easily enough, use it. And what does a race weekend's worth of Avgas and pump fuel cost compared to the classic race fuel?

Race fuel sells in even lower volume than Avgas, again, small batch and testing ensures consistency, at even more cost.

My issue is that I have never had easily access to Avgas or I would have used it regardless of compression ratios and ended up with jetting to suit.

In the UK today I would use the race fuel. It is too easy, they bring it to you, in a drum!

Add up all of the costs of a race weekend, add the potential cost of engine damage, and the extra fuel cost on a race weekend is not that great at all.

Hi Steve's
My brother paraded my Rob North for a few years. When my Norton ignition played up for a whole meeting, I rode the North. I came in & said it's got a warped disc, my brother seemed surprised! Which one he said. The right one I said. I swapped it for the rear disc as I try not to use the rear with my leadened feet. Transformed.
Feel wise was a slight flutter through the lever that went away as you pulled the brake on harder. Full on the front end hammered & you could feel which disc & physically feel & see the front end judder. Foggy Esses the chicane at the end of the back straight at Donington. The rest was manageable. All new kit at the time, so worth checking.

SteveA said:

I sort of feel you are really asking....did changing the mix ratio affect the jetting? Well it does anyway, because you are changing the oxygen ratio by reducing the Avgas.

That is part of what race fuels are about, not just detonation.

Clearly you have not had cause to question the quality of pump fuel before, so clearly any issues don't show at 50/50. A lot of tuners use nothing else but 50/50 mix. Avgas costs because of the lower volume it sells in compared to pump petrol, and because it is regulated for aviation use, which means more testing of the product as actually delivered to airfields.

Stick to a successful formula, i.e. 50/50 if you can get Avgas easily enough, use it. And what does a race weekend's worth of Avgas and pump fuel cost compared to the classic race fuel?

Race fuel sells in even lower volume than Avgas, again, small batch and testing ensures consistency, at even more cost.

My issue is that I have never had easily access to Avgas or I would have used it regardless of compression ratios and ended up with jetting to suit.

In the UK today I would use the race fuel. It is too easy, they bring it to you, in a drum!

Add up all of the costs of a race weekend, add the potential cost of engine damage, and the extra fuel cost on a race weekend is not that great at all.

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You are of course right, I am trying to understand what was happening. I am struggling to believe that 1 point of advertised octane rating could have such a dramatic effect on the way the engine ran, and if the fuel does test at 99 RON, and the avgas at 100, then something else must be happening.

I will be picking up some more avgas this weekend and will rig up a 1ltr test bottle with a small jet in the bottom and record the time it takes to empty with both fuels and then a mix.

If there is a difference and I find myself without avgas again for any reason, I will jet to suit and hopefully reduce the effect of straight VPower. I may be up around the compression that Nigel is using and he uses pump fuel without issue so I have a feeling that re jetting would help.

Of course the preferred solution is not to run out of avgas and carry on with the 50/50 mix as I have had no running issues with that.

When I rang my man at the airfield a few weeks ago, he wasn't there and I was told he wasn't in until Friday, the following week I rang Sunday morning and was told he only works Friday and Saturday. That small difference in how the information was given, is what caused the problem, I rang him the following Friday (just before setting off for Cadwell) and he couldn't help before Saturday. He is the fire officer and used to be there all the time, but due to Covid he is now part time furloughed, I guess nothing will catch fire because it is Covid that is keeping him away.

I really didn't think it would be such a problem so just arranged to pick some up this weekend, another lesson learned.

I have just done the sums and I have another quandary, I forget how much he charges for the avgas but I round it up and give him £2 a litre, add VPower at around £1.54 a ltr and 80 ltr of either my mix or the classic fuel solutions stuff is about the same price, the classic fuel is cheeper if pre ordered and payed for.

I haven't used the Classic fuel because my dyno man told me it wasn't very good, I guess he could see a power difference as higher octane fuel burns slower, personally a couple of BHP isn't that important to me as I feel I still need to learn how to race and that is where the biggest improvement in lap times will be. I think I will put an order in for Donington and do some testing.

Am I having fun yet?

Hmm, just noticed that Classic fuels say the fuel cannot be used with lambda sensors, I wonder if that is why my dyno man doesn't like it.

storm42 said:

Hmm, just noticed that Classic fuels say the fuel cannot be used with lambda sensors, I wonder if that is why my dyno man doesn't like it.

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I took my bike to Steve Jordan to get the fuel/carbs sorted on the dyno. They were quite specific, non leaded fuel, to the point they took my fuel out and gave it me back in a plastic container. As you say I think their sensors can’t handle leaded.

storm42 said:

Hmm, just noticed that Classic fuels say the fuel cannot be used with lambda sensors, I wonder if that is why my dyno man doesn't like it.

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That will be because there is lead in it....and there is lead in Avgas...Lambda sensors are generally designed to work with catalytic converters....a no lead environment!

As for not being much good, some people reportedly complained about it, but...they had assumed they should mix it 50/50 with pump fuel...like they did with Avgas...and they did that...which of course is silly because...it isn't Avgas...it is pretty much what you get when you mix Avgas and pump fuel 50/50!!!

I think the real plus is, it is more consistent, because you have taken the inconsistent ingredient, pump fuel, out of the equation.

Chris said:

Hi Steve's
My brother paraded my Rob North for a few years. When my Norton ignition played up for a whole meeting, I rode the North. I came in & said it's got a warped disc, my brother seemed surprised! Which one he said. The right one I said. I swapped it for the rear disc as I try not to use the rear with my leadened feet. Transformed.
Feel wise was a slight flutter through the lever that went away as you pulled the brake on harder. Full on the front end hammered & you could feel which disc & physically feel & see the front end judder. Foggy Esses the chicane at the end of the back straight at Donington. The rest was manageable. All new kit at the time, so worth checking.

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Hi Chris, didn't see you at Cadwell, are you going to Donington?

Hi Ralph
I'm entered, unfortunately I've just buried my Dad so really do need to get out on track & clear my head.
Mind you just started going through the bike & I'm hoping to put some new yokes on the Dresda as I've entered the triple in F750 just to get it out!
It will be good to catch up
All the best Chris

Sorry to hear about your dad Chris, like you say be good to catch up at Donington, glad you will make it.

Prep

Chris said:

Prep

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Looking good, though how old is that front tyre it looks like its from another era. We need to get the Norton twins back on the track!

I think I have solved the brake judder, I am almost certain that the problem lay in the disc carriers and disc retainer, somehow the discs were getting off the perpendicular. I am a dab hand at taking the front wheel off and putting it back on with the amount of practice I have just had, there are sharpy marks all over the front end, the measuring tool was a long piece of wood that I used as a paint stirrer and the noise it generated when held against rotating metal gave a musical indication of run out. Still needs to be reassembled but initial inspection is promising.
The oil tank and oil leaks stems from an ill fated attempt to plumb the crank and timing case breathers overboard via the oil tank. I have decided the breathers are going overboard via a catch tank which is in the seat hump. The tank hoses and clips are being replaced by AN -6 hose fittings. I am robbing the oil tank off the project bike.

I have assembled a bunch of fastners, threaded bar, bushes and rubber fittings to resolve the headsteady problem for the next couple of meetings. I plan on redesigning it over the winter. I do not have a lathe but do have an old British bench drill in good order which should be enough, failing that there is a good machinist/welder down the road who understands my drawings.

All of the above has got to be worth 2 seconds a lap c u there