Tuning For Speed

acotrel

acotrel

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I was thinking about the thread which relates to fitting a 2S cam. The way I ride, smooth power delivery is very important - probably more important than actual power delivered. To ride faster when on a lean, we become tyre dependent and that dependency is relative to the amount of lean. I got very tangled-up when I was trying to figure-out steering geometry. When I studied physics the resultant force was calculated by adding vectors. When you have a wheel spinning, the force vector direction is through the centre of the wheel, and I cannot remember in which direction it goes. When I was a kid, we all used to avidly read Phil Irvings book tuning for speed. It told us nothing about race bike construction and the way the type of power delivery is relevant.
With Manx Nortons, the power delivery was fairly gentle and the steering had a lot of trail, so the bike self-steered in the correct direction, if you gassed it when on a lean. Most bikes will do that, even if they have neutral handling. It is actually difficult to lean a Manx more that it wants to go due to it's set-up - a Triton is usually easier because the motor is back a bit. But cannot be ridden as fast.
A Commando must have less trail than a Manx or more guys would be crashing. So the amount of lean in corners should be greater. To my mind, a Commando engine should be fast enough with only minimal modification. The crank balance factor is a problem, but can be fixed. For speed work, the standard gearbox is useless.
Thev tyre thing is strange. With my bike, I have found that if gas it very early in corners, I can use it like a drag bike, and ride under and past most of the others. It is really silly stuff and potentially dangerous. You can meet the leader as they come down from the ripple strip.
When you need to counter-steer a Commando going into corners, that is understeer, and a symptom of insufficient steering trail. My bike simply gets flicked into corners and gassed. It over-steers both going in and coming out.
Less trail makes the bike more stable,and causes more lean in corners. Then you need better tyres.
 
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It is very easy to conduct an experiment to ascertain whether or not handlebars are useful in turning.

Lock the steering. Simples, lock the yokes solidly so that the bars cannot be turned.

Now go for a ride.

Report back.
 
Or ride along sitting upright and push the left handlebar forward with the palm of your hand
See which way you go
 
Fast Eddie said:
It is very easy to conduct an experiment to ascertain whether or not handlebars are useful in turning.

Lock the steering. Simples, lock the yokes solidly so that the bars cannot be turned.

Now go for a ride.

Report back.
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Keith Code has a bike set up like that at his riding school. You can lap just fine.
 
Fast Eddie said:
Correct. He did build a bike like that.

It did NOT ‘lap just fine’.

It was built to prove to people that THEY COUNTER STEER whether they realise it or not.

No B.S. Machine | California SuperBike School

superbikeschool.com superbikeschool.com
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Been a long time since I read that article, right after he had built it. My foggy memory was telling me he could ride it almost normally... but YES, you MUST counter-steer (although the amount of steering input is minscule).
 
A 2S cam will just make it come alive even quicker when in a corner when you put on the power, but a 2S cam will only work better if the ports are opened up have a good ignition, well tuned carbs and exhaust system, do all that and a 2S cam works so well without over doing it, making it breath will make an 850 come alive.
 
Fast Eddie said:
Correct. He did build a bike like that.

It did NOT ‘lap just fine’.

It was built to prove to people that THEY COUNTER STEER whether they realise it or not.

No B.S. Machine | California SuperBike School

superbikeschool.com superbikeschool.com
Click to expand...
The only time you counter-steer is when braking into a corner ,if your bike has neutral steering or understeers when ridden. normally - and most road bikes are like that. . As you brake the rake and thus trail decreases and the bike becomes more stable, If your bike understeers as you brake into a corner, it will also understeer as you accelerate out of the corner, and tend to run wide. If the trail is increased, you can flick the bike into corners and accelerate through them. But there is always a downside to everything.
Have a ride on a Manx Norton. You can gas it where normally you can not with other bikes. I did not know why they were so good until I rode one.
If your front brake drags while racing, it can cause you to run wide in corners. It causes the front of the bike to go down, and causes understeer. The reason steering can be confusing is the resultant force when you steer is found by adding vectors. One vector is through the centre of the front wheel. When you lose the front wheel under brakes the tank-slapper involves a very large resultant forces, even when the bars are barely moving. Drum brakes can be very dangerous.
 
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ashman said:
A 2S cam will just make it come alive even quicker when in a corner when you put on the power, but a 2S cam will only work better if the ports are opened up have a good ignition, well tuned carbs and exhaust system, do all that and a 2S cam works so well without over doing it, making it breath will make an 850 come alive.
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Have you ever tuned a Commando motor without changing the cam ? Opening the ports up can destroy torque. But with torque it is impossible to know you have improved it until you raise the overall gearing . - Commando motors usually have poor throttle response due to the heavy crank, so always tend to spin up at the same rate regardless of the gearing. Lowering the gearing on a Commando with not usually give you increased acceleration. The way to increase acceleration is more gears and closer and make the heavy crank work FOR you, instead of against. Also the shape of the carb needles has an effect. The taper compensates for loss of vacuum - with close ratio gears, loss of vacuum is less. So with rich needles the motor will be slower than with lean needles - you do not need the quick taper, when you have close ratio gears.
From what I have experienced with my 850 motor - as standard they are probably very good, except for the crank balance factor - their stumbling block is the gearbox.
One day I will ride my Seeley 850 with the 6 speed TTI gearbox. When I was using the 4 speed Manx cluster, it was good. But with 6 gears close ratio, it should be a real whiz.
I suggest Commandos were very under-rated. I love the motor.
 
The last time I raced, I was slow off the mark because of the high first gear, but I was quicker everywhere else. With two more lower gears, the bike should really get going. I have gone up one tooth on the engine sprocket. It can handle that,
 
Al you have never ran a 2S cam so you will never know and as for my porting its was done to make everything flow better and not over done, my Norton is a street bike and the 2S cam is still very smooth with a bit more oooof to it and a bit more compression with my head slightly shaved and yes I been tuning my Norton since new and I know what's best for my Norton as it was an everyday rider from new till 2013 and the work done to my motor has been the same since 1982 with a few better upgrades in that time, I might not be no expert but I do have a sweet running Norton that is very reliable, so I must be doing something right.
When my Norton was stock Commando from new it valve bounced at 6500 RPM and ran out of oooof, after the conversion to the Featherbed frame in 1980 to 1982 and the work done to my motor it will run freely to 8000 RPMs and more if you let it, but I do know its limits before it goes bang, I built my motor to the high performance secton of my workshop manual for a street Norton, it also had the specs for a race motor, it had everything in it to soup up and make the motor run more freely, drawings for head work, cam and pushrods as well more and of course I did the crank balancing for running hard mounts and to have a smooth running motor, all this done back 40+ years ago and my motor is still going strong and I am still running the original valves that my Norton came from the factory.
From 1976 when I brought it new I average between 10k miles a year some times less, so it has clocked up a lot of road miles since that time and now its semi-retired since my modern Thruxtons took over everyday service in 2013, but I still ride the Norton regularly and it still puts a smile on my dial every time I take it out, it's no show pony and is showing its age, but its well ridden and still very reliable and it's the way I like it, its ageing gracefully just like myself and at lease I am still riding my beloved Norton and not sitting in the shed and talking about how good it was.
I built a light weight, great handling bike and a motor that makes me show up a lot of modern bikes for its age and I did it with my own hands with only motor work out sourced or where I worked at TAFE.
So Al I do more than talk about when I use to ride it as I still do and my wife she has no say in what ever I do with my bikes, in fact she knows when I need to get out and away with my bikes, she would never tell me not too.
My Norton is built for me and no one else, I have nothing to prove to no one, I don't care about how fast it will go or I don't care about others bikes, I just care about my own and the pleasure it gives me every time I take it out and the only time I do any work on it is general maintenance and a few new upgrades that I have done over the years to make even better.

Ashley
 
ashman said:
Al you have never ran a 2S cam so you will never know and as for my porting its was done to make everything flow better and not over done, my Norton is a street bike and the 2S cam is still very smooth with a bit more oooof to it and a bit more compression with my head slightly shaved and yes I been tuning my Norton since new and I know what's best for my Norton as it was an everyday rider from new till 2013 and the work done to my motor has been the same since 1982 with a few better upgrades in that time, I might not be no expert but I do have a sweet running Norton that is very reliable, so I must be doing something right.
When my Norton was stock Commando from new it valve bounced at 6500 RPM and ran out of oooof, after the conversion to the Featherbed frame in 1980 to 1982 and the work done to my motor it will run freely to 8000 RPMs and more if you let it, but I do know its limits before it goes bang, I built my motor to the high performance secton of my workshop manual for a street Norton, it also had the specs for a race motor, it had everything in it to soup up and make the motor run more freely, drawings for head work, cam and pushrods as well more and of course I did the crank balancing for running hard mounts and to have a smooth running motor, all this done back 40+ years ago and my motor is still going strong and I am still running the original valves that my Norton came from the factory.
From 1976 when I brought it new I average between 10k miles a year some times less, so it has clocked up a lot of road miles since that time and now its semi-retired since my modern Thruxtons took over everyday service in 2013, but I still ride the Norton regularly and it still puts a smile on my dial every time I take it out, it's no show pony and is showing its age, but its well ridden and still very reliable and it's the way I like it, its ageing gracefully just like myself and at lease I am still riding my beloved Norton and not sitting in the shed and talking about how good it was.
I built a light weight, great handling bike and a motor that makes me show up a lot of modern bikes for its age and I did it with my own hands with only motor work out sourced or where I worked at TAFE.
So Al I do more than talk about when I use to ride it as I still do and my wife she has no say in what ever I do with my bikes, in fact she knows when I need to get out and away with my bikes, she would never tell me not too.
My Norton is built for me and no one else, I have nothing to prove to no one, I don't care about how fast it will go or I don't care about others bikes, I just care about my own and the pleasure it gives me every time I take it out and the only time I do any work on it is general maintenance and a few new upgrades that I have done over the years to make even better.

Ashley
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The trouble with street bikes is they are usually tuned on public roads, and most are probably jetted too rich. If you put a road bike onto a race circuit and tuned it, you would probably be amazed at the difference in performance. The problem is race tuning does not stay tuned, especially when petrol is the fuel. The standard cam in a Commando 850 has timings similar to a Triumph race cam. The mistake I made was in underestimating the worth of the 850 motor. I suggest they must be very correct in their design. Mine is much better than I ever thought it could be. I am 81 - I have been playing with hotted-up motorcycles since I was 15.
 
Jetted to rich hey, my plugs tell a different story, they run a good colour and in my book just right, I get long life out of my plugs but that is from a good spark from the Joe Hunt magneto, even after 35k road miles and were still running good with a good colour to the plugs, I only changed them as I gone back to running my old Amals so a fresh set of plugs, if my Norton was tuned too rich you think I would have got so many miles on those N7YC plugs.
In you own admission you stop riding on the roads in your mid to late 20s and when you did get on the track you had long breaks in between track days and how long now over 10 years of not riding.
Al you have never ridden an 850 Commando with a 2S cam so you will never know how much of a difference it's makes over a standard cam.
You might have been playing with hotted up bikes from 15 but in your own admission not much time on the roads and by your admission not a great deal of track time with lots of long breaks, I been playing with my Norton since I brought it new when I was 17 converted to the Featherbed in my 20s (1980) and the motor built and hotted up for the road at the same time and the motor is still the same since 1982 and has never been off the road for long with one major rebuild and a few upgrades since and all work by my own hands, and I can take it out anytime I want.
It's good to brag about how good your bike is and if it's so good why are you no longer riding it.
Racing can be expensive and limit times you get out to ride, why I ride on the road, in fact might take the Norton for a run tomorrow, I need a break from the Land Rove/camper project.

Ashley
 
The reason I am no longer riding it is because my wife is a woman. They think everyone is going to be killed or maimed. She was watching the last time I raced. For the first time in my life the fuel line came adrift - just after I had passed the three leaders in turn two at the start of a race. I had them cold. Normally I do not ride through the middle of a bunch of riders in a corner. In the first two races I could not get a good start. In the third, I had revved the tits off the motor and risked it, so when the others all went wide, I just rode under and past them. The three bikes I passed were Rex Wolfenden's 1100cc CB750s - we were all on methanol.
It was all pretty tame stuff, but an onlooker has a different perspective. When I was talking to my wife last night, I felt I was making progress, but she is still very doubtful. My main helper is dead and gone, so that is not good.
 
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