Compression and Ignition

johnm

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Hi John,

The bit of the Jennings article that I found really useful is where he describes looking at the plug for signs of erosion and over heating and then reducing the advance 2 degrees at a time until you get the burn and plug colour characteristics he describes with the burn "just a hair short of the end of the electrode". I also found with the new plugs you can clearly see the pepper specks on the white of the center insulator if you are too far advanced.

I have seen many plugs in the pits with tiny spheres of aluminium on them clearly indicating too much advance. People then flood it with fuel and instal really cold plugs to try and stop it.

It is probably not important with your ignition but with a magneto it is really important to check both cylinders because a lot of mags have very different timing on each magneto cam lobe.

Be aware if you go the expensive racing Avon way that at least up to three years ago these tyres have a limited number of heat cycles in them before thay go off. They can still look good but they will break away big time without warning. Problem is no one will tell you how many heat cycles are too many. I used to figure on about 25 and then throw them away. With our short races plus practice this means a new set of tyres about every four or five meetings - big money at $800 a set.

I agree with you as well about being out having fun. For many reasons I didnt start racing until my late 40s and Im a bit too competitive. I was not fit enough and pushed to hard beyond my skills and had a massive highside at Taupo breaking a few bones. You dont bounce so well when you are in your fifties :)

Cheers
John
 
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X-file said:
It comes from experience with one fast,but almost standard (we used standard parts,slightly massaged),R100 S .You can get 10.5:1 just by leaving out the head gasket,but even with the gasket it went well.

Have a look in the manual or parts book at the early clutch.The wrong part of the diaphram spring is pushing on the clutch plate,and it doesn't exert much force.
It got corrected on the later clutch.

If it goes well,you need the later clutch.
I'll run that by the local BM guru, next time I spot him.
You used all stock 1000 clutch parts ?
The 1000 clutch is thicker than earlier versions (and thinned flywheel), parts probably can't be mixed.
This before the whole clutch was made lighter.
 
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Rohan, the BMW Rennsport sidecar I referred to is the one that Orrie Salter brought back from Europe in about 1962. A friend of mine was his passenger in Europe. Orrie brought it to Phillip Island and beat all the 1000cc unlimited sidecars with it. It was the genuine 500cc factory bike, and it was supposed to be returned to the factory. Orrie simply kept it. It appears to have been in the possession of Stan Bayliss for yonks, and when he died his wife became owner. She sold it to a guy in Queensland who is converting it into a solo. I'm not big on sidecars , however I could never do that to something so genuine. It's a sad fact of life that many often don't recognize the intrinsic value of some of the older bikes. I'm sorry that I haven't got a better bit of video, but you can get a glimpse of the bike, Sidecar No 1.

http://www.youtube.com/watch?v=8iC5FD266jg
 
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Rohan, two seconds in history (1962). You can see the camshaft drive, it is not an imitation :

 
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In your race class can you go to twin plugs?

If so a reliable way to increase CR without pinging. Usual airhead full advance is at 32 degrees, you might need to retard if you are pinging.

One way to check would be to run a set of alternative curves on the DYNo, going for mavimum torque coupled with power WO Pinging. It depends if you can get some dyno time at a reasonable rate.

If you go onto the Sachse website,mthey have graphs for the 9 ignition curves that they offer, same as for the 16 curves that silent Hektik Provide on their website.
 
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If I am using petrol, I usually set the ignition advance as per the manufacturers' specification for a standard motor, or add 4 degrees for methanol. Then I tune the carburation with that and the compression ratio fixed. If you use two plugs per cylinder, it is usually difficult to know if they are both firing. I suggest you need to reduce the number of variables to a minimum, and only change one thing at a time and try to appreciate whether there is an improvement in performance - i.e. ride the bike on a race circuit. If you increase the compression ratio, you would obviously have to watch your jetting. I simply don't believe that carburation can be optimized on a dyno, however if you are changing ignition timing, it could help. You will find that from full retard to advance the motor goes from sluggish to distress for a given carburation setting. It is a matter of picking best performance , however ignition advance , carburation and comp ratio are inter-related so go carefully or you could do damage.
 
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acotrel said:
It is a matter of picking best performance , however ignition advance , carburation and comp ratio are inter-related so go carefully or you could do damage.
And, oddly, this is about where we came in.
Most dyno shops can monitor various things, including exhaust gas composition and temps - so the chance of doing any damage while on the dyno is about nil....

Old school is not always best, these days.
Do what the fast folks do.....
 
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Rohan said:
acotrel said:
It is a matter of picking best performance , however ignition advance , carburation and comp ratio are inter-related so go carefully or you could do damage.
And, oddly, this is about where we came in.
Most dyno shops can monitor various things, including exhaust gas composition and temps - so the chance of doing any damage while on the dyno is about nil....

Old school is not always best, these days.
Do what the fast folks do.....
LOL, yes.
The bike was set up by a combination of others input, the manuals, various BMW forum keysperts and trial and error. If the motor was going to blow up its had plenty of opportunity running at 7500 thru the gears.
I acquired enough parts to make another engine at 1000cc but now the challenge to me would be to try and make the 900 go better.
I've got some later heads, but have no idea how to eek more out of them, the BMW guys unlike the Commando ones keep the secrets to themselves.
I'm thinking more flow at high velocity, lighter valves, beehive springs, titanium retainers, less flexible pushrods...they are nearly a foot long :shock:
A thought out 2 into one might be good too.
Cheers
John
Got sent this pic from last meet :D
 

johnm

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Rohan said:
acotrel said:
It is a matter of picking best performance , however ignition advance , carburation and comp ratio are inter-related so go carefully or you could do damage.
And, oddly, this is about where we came in.
Most dyno shops can monitor various things, including exhaust gas composition and temps - so the chance of doing any damage while on the dyno is about nil....

Old school is not always best, these days.
Do what the fast folks do.....

If only it were true.

Unfortunatly my personnal sampling is that only about 1 in 4 operators in NZ can be trusted to operate a dyno correctly and have the experience and training to work on the development of older machinery.

Many lack good understanding of the software and know nothing about megaphonitis, older carbs, magnetos etc.

Plus their HSE standards leave a lot to be desired. Loose tiedowns being caught in wheels and chains, methanol fumes etc. Running engines way to hot with poor airflow cooling from the fan systems.

So use dynos but keep a good eye on what is going on.
 
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Rohan, I'm actually an industrial chemist. How do the dyno guys get a usable response time out of the exhaust gas analyser ? Some of these black boxes look good, however the accuracy and precision may be suspect and it is easy to deceive yourself that the results mean something. Plenty of motors have been destroyed on the dyno, and in any case carburation and gearing and torque requirements depend on the circuit. I suggest that getting good numbers on the dyno is not the be all and end all. You can find yourself with a bike which really flies on a big circuit, however is a pig on a tight twisty one. My Triumph was like that. When I finally sold it after 12 years racing, I only felt relief. My Seeley 850 is a completely different kettle of fish, when I think about riding it I only feel enthusiastic - no feelings of extreme anxiety. Before my friend died a few months ago, I discussed the time he rode the Triumph 500 at Bathurst. He came to the end of Conrod Straight, and was going so fast that he could not stop it - had to choose whether to take the escape road to the right, or turn left and keep going. Either option was a big crash. So he got around Murray's corner, and up to Skyline where he bounced off the Armco fence and broke his arm and leg. He did not race for nearly twenty years after that, and he was certainly no chicken. He was the Hartwell Club champion in the mid-fifties, and an extremely good rider. When I started racing that bike, I was a pretty good rider however it turned me into an instant dud. Exciting, but a dangerous shit heap !
These days I ride my Seeley like I am a gecko lizard. I will never come unstuck off it, I've had too much crashing experience , and it is so much easier.
 
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Rohan
'Old school is not always best, these days.
Do what the fast folks do.....'

The 'fast folk' historic guys in Australia ride vastly overcapacity bikes with a 'bigger is better, point and squirt' mentality. Our local circuit is about one half tight and twisty. They can be beaten - 'torque wins races'.
 
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O2 sensor is fast enough to run fuel injections reliably and efficiently.
Kock sensor too, although I don't know if anyone applies that to bikes ?
CO sensor is not slow either.

There are a few ES2 Nortons racing in classic racing that taught the manxes a thing or 2 about how a single should go - they didn't get developed that far by accident.
NZ and Australian examples too...
 
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72Combat said:
I've got some later heads, but have no idea how to eek more out of them, the BMW guys unlike the Commando ones keep the secrets to themselves.
I'm thinking more flow at high velocity, lighter valves, beehive springs, titanium retainers, less flexible pushrods...they are nearly a foot long :shock:
A thought out 2 into one might be good too.
If you keep it 900cc and only rev to 7500,I'd keep the intake port diameter less than 31 mm.Only enlarge it a little to get around the valve guide,about 30% more area.You can taper it up to match the 36mm carb with about 7 degree included angle.

Standard valve springs on the R100S are OK to about 8500 rpm.I wouldn't waste money on beehive springs or titanium.You can lighten the standard spring collars a little by grinding them squarish.I've not noticed any flow improvement from a smaller valve stem.There's very little power to be gained by lighter valvegear and lighter springs.Most of the valvegear kinetic energy is returned to the camshaft when the valve closes,with little lost to friction.

Industrial strength pushrods would be good.Bigger diameter is always better,even at the same weight.

2 ito 1 is worth a shot.You could pick up twice as much in the mid-range as you lose at high rpm.

I tend to agree with acotrel.The dyno is just a guide.What happens in the real world on the road will be different.You can't set mixture by a gas analyser;it's only a guide if you're a long way off.Set the mixture to get the most power,even if the AF ratio looks wrong.
 
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Rohan,beating manx nortons with an ES2 is an expensive exercise. Doing it with a two valve speedway Jawa engine is much cheaper.
 
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'I tend to agree with acotrel.The dyno is just a guide.What happens in the real world on the road will be different.You can't set mixture by a gas analyser;it's only a guide if you're a long way off.Set the mixture to get the most power,even if the AF ratio looks wrong.'

The greatest limiting factor in building any race bike, is usually the gearbox. If you cannot get that optimized to suit the circuits, the rest won't help much. I'd love to build a BMW racer, but the diff and lack of sprockets is a turn-off. Can you change overall gearing by the gears at the back of the gearbox? - Even that would help. If you actually achieve a significant gain in midrange, you would probably have to up the gearing to keep the bike sensible. Can you buy a close ratio box for a BMW ?
 

johnm

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Just a bit of clarification from my side.

I used an inertia dyno to help develop my bike. It could also be run in brake mode to tune at specific rpm points. It helped me develop the bike a lot more quickly than would otherwise have been possible.

However I did find many (most) operators were not so helpful for older machinery and while no engine damage was done one operator burnt out and destroyed a clutch by setting the drum load too high on the computer and then insisting it was the bike not the dyno at fault.

It is possible to get an ES2 to beat a Manx. But at least the NZ ES2 version is a bit delicate and this is the shop owned by the guys who built that ES2

http://www.serviceengineers.co.nz/compa ... ut-us.aspx

The machine shop

http://www.serviceengineers.co.nz/compa ... -shop.aspx

Not your average back yard shed.

Having said that about 4 years ago my clubmans Dommie and their clubmans ES2 went head to head at the NZCMRR Classsic Festival. Final score was 1 to the Dommie 2 to the ES2. My Dommie was ridden by Tony McQueen a forty plus year old guy who last seriously raced bikes in the 1980s. The ES2 was riden by Sam Smith who had won the NZ 600 cc Production championship that year. A couple of years earlier he had been runner up in the Australia 125 title support class at the World Superbike round at Phillip Island. They were awarded the Classic dice cup for the meeting. So those ES2 can be beat !!

(To be fair I should add Tony is a fair rider and beat Stroud back in the 80s before he became a Honda works rider and runner up in several world superbike titles. I really beleive that if he had listened to a manager telling him when to behave he could have been a world champion level rider). Even 20 years ago top racing was as much about being a ambassador for your company as being fast on the track.

Jawa speedway engines are actually specifically excluded under NZCMRR rules.
 

johnm

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Sorry last thing.

- to the question of converting dyno results to the real world.

Early on I said to try and get the dyno results on a memory stick so you can put them in a spread sheet.

Clubmans rules in NZ say 4 speed boxes. Plus we have short races so the start is very important. So first gear is devoted to getting to the first corner first !!!

But for the rest of the gears get the dyno torque curve. Work out your rpm drop between gears and either adjust your ratios to suit or your header lenght to get the power curve in the right place. Once you have calibrated on a few tracks you can then set up for any new tracks by taking a photo or map off google earth, scale the lenght of the straights and select gearing accordingly. This works and the only time I screwed up was the first meeting at Hampton Downs. Theres a hill leading onto the front straight !!!!!!!! Hills dont show up on circuit maps! - Over geared!!!

John
 
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X-file said:
Most of the valvegear kinetic energy is returned to the camshaft when the valve closes,with little lost to friction.
Maybe at idle but far from accurate statement as the engine speed increases. To illustrate, take this to an extreme point of just at valve float; most all the energy that goes into opening the valve and is lost.
 
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I've found the gearing on my Seeley 850 to be extremely deceptive. It was coming up too quickly through the gears (no lag) so I took a couple of teeth off the back sprocket, the bike just went quicker everywhere but off the start line, where it was impossible. And it still came up too quickly through the gears. I never thought of using a very low first gear in the CR box, to get the bike quickly off the start line. I still don't know what gearing my motor will actually pull down the long straights on our local circuit. It is certainly fast enough to win if I can fire up enough. I like this bike a whole lot, even though it is garbage. It tends to grow on you by inspiring confidence?
 

johnm

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acotrel said:
I've found the gearing on my Seeley 850 to be extremely deceptive. It was coming up too quickly through the gears (no lag) so I took a couple of teeth off the back sprocket, the bike just went quicker everywhere but off the start line, where it was impossible. And it still came up too quickly through the gears. I never thought of using a very low first gear in the CR box, to get the bike quickly off the start line. I still don't know what gearing my motor will actually pull down the long straights on our local circuit. It is certainly fast enough to win if I can fire up enough. I like this bike a whole lot, even though it is garbage. It tends to grow on you by inspiring confidence?
When I got rich and decided to go to open class I bought a six speed TT box. First gear is stock standard Commando first gear ratio. Now Tony can soemtimes get to the first corner ahead of any 500 in NZ.

The need for CR boxes grew from european racing, long open circuits, push starts.

For Australasian sprint races, mostly run on poormans, small tight club and street circuits they are often not the best answer in my opinion.
 
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