PW3 Camshaft

Fullauto said:

Another interesting thing. I had reason to change the Tri-Spark recently, so I set the timing roughly and proceeded to run the bike for a couple of weeks before it could be set more accurately. It ran very well with just an annoying habit of being hard to start from cold. When it was checked, I'd been running 36 degrees of advance with no ill effects. In previous incarnations, it has always let me know it was unhappy by pinging while accelerating from low revs in warm weather, running 98 octane, even if the timing was correct. I'm now running 95. This tells me that the coatings on the piston tops, ports, combustion chambers and valve heads are working as they should. I can highly recommend the ceramic coating of engine components.

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Normally ceramic coatings will increase the tendency to ping. With the ceramic coating the hot mixture looses less of it's heat to the surrounding chamber and piston which means you need more octane to prevent ping.

Of course the big cam will drop the cylinder pressure and with it goes the tendency to ping. Jim

comnoz said:

Fullauto said:

Another interesting thing. I had reason to change the Tri-Spark recently, so I set the timing roughly and proceeded to run the bike for a couple of weeks before it could be set more accurately. It ran very well with just an annoying habit of being hard to start from cold. When it was checked, I'd been running 36 degrees of advance with no ill effects. In previous incarnations, it has always let me know it was unhappy by pinging while accelerating from low revs in warm weather, running 98 octane, even if the timing was correct. I'm now running 95. This tells me that the coatings on the piston tops, ports, combustion chambers and valve heads are working as they should. I can highly recommend the ceramic coating of engine components.

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Normally ceramic coatings will increase the tendency to ping. With the ceramic coating the hot mixture looses less of it's heat to the surrounding chamber and piston which means you need more octane to prevent ping.

Of course the big cam will drop the cylinder pressure and with it goes the tendency to ping. Jim

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You're a genius! That explains it.

What I'm saying is that it was a bit much for the standard motor but i could use a 23 tooth with ease now. I've had up to 68mpg tooling around town. I haven't had less than low 60s even when using the midrange to move along. When I had an 850 back in the seventies, 42 to 43 mpg was as good as it got.

Fast Eddie said:

toppy said:

Oh where will it all end

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Such innocence and naivety..!

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I wish i was naive Eddie. If i added up what i have spent on bikes an cars over the years i could buy a better house than the one am still paying mortgage on. But i don't add it up or find houses as much fun either so it doesn't keep me awake at nights

toppy said:

Fast Eddie said:

toppy said:

Oh where will it all end

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Such innocence and naivety..!

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I wish i was naive Eddie. If i added up what i have spent on bikes an cars over the years i could buy a better house than the one am still paying mortgage on. But i don't add it up or find houses as much fun either so it doesn't keep me awake at nights

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I never add it up either. Never have. I know it would have a negative effect ... Especially on the wife ...

I'm a simple chap, so have a simple philosophy:

Don't spend what you're not happy spending.

Only spend what you're happy to spend, on what you're happy to buy, and move on!

Fast Eddie said:

I never add it up either. Never have. I know it would have a negative effect ... Especially on the wife ...

I'm a simple chap, so have a simple philosophy:

Don't spend what you're not happy spending.

Only spend what you're happy to spend, on what you're happy to buy, and move on!

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Sounds like a good philosophy to me. I can't understand people that think of bikes or cars etc as an investment. For me its a hobby an i didnt enjoy it i wouldn't be doing it.

toppy said:

Fast Eddie said:

I never add it up either. Never have. I know it would have a negative effect ... Especially on the wife ...

I'm a simple chap, so have a simple philosophy:

Don't spend what you're not happy spending.

Only spend what you're happy to spend, on what you're happy to buy, and move on!

Click to expand...

Sounds like a good philosophy to me. I can't understand people that think of bikes or cars etc as an investment. For me its a hobby an i didnt enjoy it i wouldn't be doing it.

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Its an investment in living a good life.

I know at least 2 philosophies of life : If you save up you might become the richest corpse in the graveyard however the richest living people in America are widows. AND 'he who dies with the most toys, wins !' - The problem is the same one we always have with projects, we need to know the deadline, so we can plan ahead.

I only ever know if I am happy to spend......after the transaction.....doh!

If you fit a PW3 cam into your motor, does that raise the usable rev range ? And doesn't fitting larger (heavier) valves lower the safe upper limit of the rev range

acotrel said:

If you fit a PW3 cam into your motor, does that raise the usable rev range ? And doesn't fitting larger (heavier) valves lower the safe upper limit of the rev range

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I, for one, don't care about maximum rev use in a Norton. My philosophy has always been to accentuate the Norton's strengths, which, to me, is that beautiful low end and mid range torque. If you want revvy, there are umpteen bikes that will fill your needs better than a Commando. I've busted an engine mounting bolt, twice now, so when my replacement arrives it's off with the primary drive to replace it. I'm now left in the position to change to a 23 tooth sprocket if I wish. I'm pretty sure I'm going to. I'm dying to see what it will be like. I'll report back.

I've never found revving the nuts off a Norton to be satisfying in any way, having some mechanical sympathy. They just never seem to be particularly happy doing it to my mind. It's like young blokes with their burnouts and wheelstands. They don't mind because they don't keep the bike long enough to deal with the mechanical consequences of their actions.

About getting performance out of old bikes - I have always believed that if you haven't got the gearbox, you haven't got the bike. My 850 motor pulls like a train. In fact every time I have raised the overall gearing, it has gone faster. The close box is essential, however with the four speed cluster, first gear is too high for comfort. After the bike staggers off and starts rolling, it is perfect everywhere on smaller circuits. The close ratios are essential for good acceleration, and the high overall gearing uses the torque to best advantage. If you can keep the 850 on the boil, it is acceptably fast. That is why good steering geometry is important - get on the gas early in corners.
The reason the Japanese bikes were so good for racing in the 70s was that most of them had 5 or 6 gears - it meant that old Brit bikes were at a severe disadvantage.
I limit my revs to 7000 RPM and I believe even that is probably too much. Above that, everything works against you. - Piston weight, valve weight, bottom end - are all potential failures. And the problem is that the revs are a linear relationship, however the accelerations and forces are all squared relationships.
If I had a PW3 cam, I would use it. However I'd stay with my smaller tapered inlet ports and my 2 into 1 exhaust system and juggle the cam timings to get it to work.

The PW3 gives me more everywhere. The broader the powerband, the less need for close ratios. Mine accelerates well, everywhere.

A lot depends on how you intend to use the bike. Close ratios on a road bike are a bit of a waste. In the past, I have also found that fitting a hot cam to a road bike usually causes the power band to be more pronounced but stronger everywhere. The exhaust system is often a limiting factor if it causes a lot of back-pressure. It is difficult to get something which resonates well, yet is quiet.

I don't think it's likely that a hot cam will make the powerband stronger everywhere, nor is it going to make an engine stronger low down in the powerband. Just the opposite.
Phil Irving covers this stuff very well in "Tuning for Speed" He explains why a high lift big overlap can loses power down low and improves power at top, essentially moving the powerband up.

He would sometimes custom grind "RV" cams for his close friends. He did this for various makes of bikes. If someone wanted bike for two up mountain touring or sidecar work, these came were ideal. He started with mild stock street cams then reground them for less overlap, more pulling power.
The engine would lose some top RPM power, but the owners didn't mind as they never went there anyway.

Glen

worntorn said:

I don't think it's likely that a hot cam will make the powerband stronger everywhere, nor is it going to make an engine stronger low down in the powerband. Just the opposite.
Phil Irving covers this stuff very well in "Tuning for Speed" He explains why a high lift big overlap can loses power down low and improves power at top, essentially moving the powerband up.

He would sometimes custom grind "RV" cams for his close friends. He did this for various makes of bikes. If someone wanted bike for two up mountain touring or sidecar work, these came were ideal. He started with mild stock street cams then reground them for less overlap, more pulling power.
The engine would lose some top RPM power, but the owners didn't mind as they never went there anyway.

Glen

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Maybe unlikely, but that's my observation. I keep hearing things from others with modded motors like "it comes on really strong over 4000", and I remember how my 850 with a Combat cam did indeed have a pronounced power step at 4500 revs. Not so with this bike. Just strong power from off idle up. I've never ridden a Norton like it. In fact, I just amuse myself thinking that this was the factory F750 racing cam in it's day, yet it is so flexible. I cannot believe that the coatings applied internally and Jim C's conical valve springs could make that much difference to the resulting power characteristics. But they are the only other changes during the rebuild. Mind you, the Fullauto Tech head made quite a difference over standard, but this was on the bike before the rebuild. I've done 25,000 miles with this head now.

I would by now have a dyno session comparing a standard 850 to mine but, my mate ran into a car on his way to licence it. Very tragic. He's ok but the bike's not too good. Trashed his front end. However, this will happen. If anybody living in Perth would like their bike dynoed for free, send me a PM.

Whenever I have fitted race cams to a road bike, it has become stronger below the 'cam spot' and much stronger above it. The bump when it comes on song might give the adrenalin rush, however it is not what you really want for fast scrapping during racing. Smooth and strong is much better. It is usually the exhaust system which affects that. These days I use a 2 into 1 exhaust - NOT megaphones on separate pipes. A vicious bike is no fun. Building an extreme racer is easy - building one which handles to the max and has usable power is not so easy.

If you want to have some fun, get yourself a 1000cc 4 cylinder Japanese bike and fit it out with a proper race cam and 4 separate pipes with megaphones, A CR750 Honda with all the kit is bad enough.

I once rode an 850 with a single Mikuni (forgot the size), Ham-can filter, peashooters, PW3 cam, and stock CR.

Below 5k it was gutless, above 5k it just wheezed breathlessly. It had neither the bottom end torque nor the top end pull that Commandos are famous for! It was awful.

Being a MK3, it had a RH4 head.

I can only assume Ken that your FA head compliments the PW3 and vice versa, in some way that 'works'. It seems the only significant difference between your bike and the one that I rode, but your description of your bikes performance bears no resemblance at all to the one I rode!

Fast Eddie said:

I once rode an 850 with a single Mikuni (forgot the size), Ham-can filter, peashooters, PW3 cam, and stock CR.

Below 5k it was gutless, above 5k it just wheezed breathlessly. It had neither the bottom end torque nor the top end pull that Commandos are famous for! It was awful.

Being a MK3, it had a RH4 head.

I can only assume Ken that your FA head compliments the PW3 and vice versa, in some way that 'works'. It seems the only significant difference between your bike and the one that I rode, but your description of your bikes performance bears no resemblance at all to the one I rode!

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Who built it?