Stock Commando Cam Specs
- Thread starter Dan1950
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- Mar 22, 2021
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Correct....Visial detection of excessive lobe wear is noticed when adjusting valve clearances (rocking the motor)
..is a very short duration ( valve no sooner begins to open... then instantly begins to close)
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- Jun 30, 2012
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When I was building my 850 motor, I took the cam sprocket to a friend who put it on a piece of firebrick, heated to red, them let it cool slowly. I then took it elsewhere and had two more keryways broached into it. It does not matter what cam or exhaust system you have, the cam timing has to be to be optimised to suit. Also you have to optimise the ignition timing, mixture and fuel.
When you theoretically compare what you have with what other people are using, there are too many variables to make a sensible comparison. A lot depends on how you want to use the bike. On a race track with an 850 Commando, if it pulls a very high gear, even then the usable rev range is usually from 5,500 RPM to 7,300 RPM. On public roads it probably never gets used like that.
What you need to do, is install your cam and progressively advance it over several track tuning sessions. However an improvement in torque is usually only detectable when you raise the overall gearing. So start tuning with relatively high gearing.
Detonation will not occur if you are jetted a bit too rich, and ignition timing is not advanced ahead of standard. Once you start to get sense out of the system, then start working on getting the jetting and ignition timing right. I usually set the ignition timing, then jet to suit it. I do not raise compression ratios.
When you theoretically compare what you have with what other people are using, there are too many variables to make a sensible comparison. A lot depends on how you want to use the bike. On a race track with an 850 Commando, if it pulls a very high gear, even then the usable rev range is usually from 5,500 RPM to 7,300 RPM. On public roads it probably never gets used like that.
What you need to do, is install your cam and progressively advance it over several track tuning sessions. However an improvement in torque is usually only detectable when you raise the overall gearing. So start tuning with relatively high gearing.
Detonation will not occur if you are jetted a bit too rich, and ignition timing is not advanced ahead of standard. Once you start to get sense out of the system, then start working on getting the jetting and ignition timing right. I usually set the ignition timing, then jet to suit it. I do not raise compression ratios.
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- Nov 11, 2013
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You should like that cam. I love mine.Another piece to the puzzle has arrived.
Did you flow your head?
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- Aug 19, 2021
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No, I didn't want to send the head out with all of the other things to keep track of.
Maybe next winter when I have fewer irons in the fire.
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You could send the head out now and maybe get it back next winter.....
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That's what I was afraid of.
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It will feel the need. The need to breathe.
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Theories are lovely, but cause and effect when you have multivariate data are not simple black and white. When you change only one variable in a motorcycle race engine, all the other things interact with it, in cluding the purpose for which the motorcycle is intended. When you fit a different cam, the exhaust system, comp. ratio, ignition advance and jertting work with it., along with the gearing and the type of circuit on which you race. Sometimes you need to advance the cam to get it to work effectively with the exhaust system. A restrictive exhaust system can cut the top off the rev-range potentially provided with a race cam. With a Commando engine, that can be an advantage if more torque happens in the midrange. But that changes the way you gear the bike and on which parts of a race circuit the bike is faster. So handling comes into the equation.
In my case, I knew what limits the effectiveness of a 2 into 1 exhaust system. I just asked my cam grinder for his best Norton grind. Then optimised the jetting and ignition timing to suit the fuel and the exhaust system. My cam sprocket has 3 keyways in it.
It probably does not matter which cam you are using as long as itb is not a valve dropper, you probably end up at the same place once you have optimised the system.
I do not know howc anyone can compare camshafts until each one has been fully optimised in simialer motorsa.
In the olden days guys used to believe 'the best motor in the best frame gives the best bike'. It is never a simple additive process.
What are the variables ? With my bike, changing the steering geometry made a bigger difference to it's performance, than any engine modification. But everything has to work together. Recognise the pasttern.
In my case, I knew what limits the effectiveness of a 2 into 1 exhaust system. I just asked my cam grinder for his best Norton grind. Then optimised the jetting and ignition timing to suit the fuel and the exhaust system. My cam sprocket has 3 keyways in it.
It probably does not matter which cam you are using as long as itb is not a valve dropper, you probably end up at the same place once you have optimised the system.
I do not know howc anyone can compare camshafts until each one has been fully optimised in simialer motorsa.
In the olden days guys used to believe 'the best motor in the best frame gives the best bike'. It is never a simple additive process.
What are the variables ? With my bike, changing the steering geometry made a bigger difference to it's performance, than any engine modification. But everything has to work together. Recognise the pasttern.
