The P11 thread

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texasSlick said:
p400 said:
has anyone replaced the entire clutch assembly? Norvill 040478, I think it is about $525 right now. Maybe even balanced this assembly? I see a similar clutch 04-0478 at Andover for $1050 Anyone use either?
For individual clutch part numbers see....http://www.andover-norton.co.uk/SI%20Clutch.htm
If your basket does not have worn sprocket teeth, the clutch center (040366), shock absorber center 040343 (spyder),and shock absorber rubbers (040386/7) may be all you need. I have found AMC Classsic Spares in the UK to have best prices. See http://www.amcclassicspares.com. Barnett has friction plates for about $65 Slick

Worn basket, worn centre, worn plates rattling on both, worn rubber, worn etc.............looks like a complete clutch is a good thing.
But I hear of quality issues around clutch pieces from known suppliers.....wobble, out of round, splines don't fit, etc.
So I am looking for intelligent, pertinent responses from clutch buyers from known sources, if anyone has done so recently.
Thanks
 
The drum/basket does not usually wear at the same rate ,all you may need is a center,plates and rubbers.
 
I had a similar situation with my 650SS clutch, plus the tin primary leaked oil. I believe it is the same clutch as your P11 has. The biggest problem was that I could not get the stock clutch to hold solid above 4 k after the head had been reworked by Norton tuner Herb Becker.
Replaced the primary drive with a Bob Newby Racing dry clutch and belt drive. It is lighter than the stock clutch and it is balanced by Bob.
Very nice clutch and drive, no drag, no slip, smooth engagement, no oil leaks!
About £425

Glen
 
worntorn said:
I had a similar situation with my 650SS clutch, plus the tin primary leaked oil. I believe it is the same clutch as your P11 has. The biggest problem was that I could not get the stock clutch to hold solid above 4 k after the head had been reworked by Norton tuner Herb Becker.
Replaced the primary drive with a Bob Newby Racing dry clutch and belt drive. It is lighter than the stock clutch and it is balanced by Bob.
Very nice clutch and drive, no drag, no slip, smooth engagement, no oil leaks!
About £425 Glen

Thank you, wrote to Bob, might be my answer
The P11 thread
 
Reply from Bob Newby -
Thank you for your enquiry. We have done a few belt drives and clutches for the P11 but the space within the Matchless chaincase is severely limited. This means that even using a narrow 25mm belt, the chaincase requires a spacer. We dont supply the spacer as this was done by the customer on our previous conversions. The cost of the belt drive and clutch is £450 + £45 shipping.
Best regards,
Bob.

I am going to guess that not only is a spacer needed between the case halves, the stator must be moved inboard, and the foot peg and brake pedal modified. So this is not a good clutch choice for me right now.
Newby showed chain clutches and I asked about chain clutches, but they do not make a chain clutch for P11.
 
I am considering JS Motorsport http://www.jsmotorsport.com/products.asp light weight pistons and long Carillo rods for replacement parts in my P11.
I am looking for experience using these two Jim Schmidt JSM products on street Nortons - P11, Atlas, others with ridged mounted engines.
Anyone with long term use of these JSM products for minimizing vibration on the street?
 

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I am trying document what an original P11 balance factor appears to be. And this must be the same for pre Commando 750. and maybe same for early 68-70 Commandos.
P11 original balance numbers in grams
original piston 220
original rings 18
original pin 70
original rod Pin End 130
reciprocating one side - 438
reciprocating total - 438 x 2 - 876
--------------------------------------------------
big end bolts shells 320
big end one side 320
big end total - 320 x 2 - 640

So I modified a wheel truing stand to accept a P11 crank resting on ball bearings
I put the piston pins back in for holding a bolt in each....and starting adding big steel washers .
I want to back calculate the balance factor.
The rough weight required to counter this assembly as shown is roughly 530grams
530 is the total weight of pins, bolts and steel washers.
Please do the math and tell me what you find for balance factor!
should I pump the crank full of oil and plug?
Do these numbers make sense?
How do I get a "bob weight"?................I figured the "bob" to be everything hanging on the crank to balance it out, two dry rods + 530.
-----------------------------------------------------------------------------------------------
530(measured with this rig) + two complete rods(900dry)=1430 bob weight?
1430 - 640(dry big ends) = 790
790/876 = 90% dry balance factor
YES !!!?
 

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What do you plan to do with this here bobweight ??

Folks that use them to spin the crank and dynamically balance it usually make their own ?
Its 2 hefty chunks of steel, that can be clamped around the big end.
Possibly with provision of adding weights to it, along the lines of your large steel washers.

Will think about your BF, lotta quoted weights there to consider.

530 grams to counter 876 reciprocating grams sounds like a 60% BF,
but need to consider if all those additions are allocated to the correct side of the equation.
Best done in the morning, after a coffee....

Does the 530 grams take into consideration the portion of the rod that is considered to rotate ??
 
Rohan said:
What do you plan to do with this here bobweight ??Folks that use them to spin the crank and dynamically balance it usually make their own ?Its 2 hefty chunks of steel, that can be clamped around the big end.Possibly with provision of adding weights to it, along the lines of your large steel washers.Will think about your BF, lotta quoted weights there to consider.530 grams to counter 876 reciprocating grams sounds like a 60% BF,but need to consider if all those additions are allocated to the correct side of the equation.Best done in the morning, after a coffee....does the 530 grams take into consideration the portion of the rod that is considered to rotate ??
see above numbers please
 
p400 said:
see above numbers please

I have. And see my questions about them.

Aren't you using the rods full weight to counteract the BF imbalance ?
Or, where is the sums to arrive at the 530 gm.

Or, why aren't you just declaring that 60% balance factor ??

Edit. Aha, you have added some figures (above)....
 
We have seen a figure of 85 or was it 86% quoted for the Atlas balance factor.
So that is not out of the ball park. Wet or dry could make a few % difference too.

Some folk have also mentioned the apparently entirely haphazard method of crank balancing employed by AMC in this era.
It was mentioned that cranks were sent outside to be balanced - which consisted of drilling random holes in the crank !?!
This may explain why some bikes were quite smooth, and others were real shakers....

Have you already ridden this bike, my memory is a little hazy of what has been said, in amongst all the P11 chat.
 
BALANCE FACTOR SCRATCH TEST TOOL

First of all - when people suggest a BF how do they qualify it? By the sensitivity of their butt and how well they remember how a Nort vibrated one day and they how it vibrated a few days later after they changed the balance factor?

The first clue is that Nortons are balanced anywhere from 52% to 80% and that 67% is the midpoint average.

Then you hear that different frames, isolastics and tilt of the motor effects everything.

And the science is confusing. If you switch a heavy rod cap to a lighter rod cap on the same rod you get difference weight measurements on the small end of the rod even though in fact the small end of the rod did not change weight (because of the way that each end of a rod is weighed horizontally). This means that OEM alum rods with heavy steel caps will give different BFs than all steel or all alum aftermarket rods - so things are screwy, complicated and messy.

There is a way to actually verify correct BF. This is the only way I know of to figure out which BFs are correct and which are just regurgitated BS. NOTE THAT THE TEST BELOW CHALLENGES THE NOTION THAT HIGHER BALANCE FACTORS WORK BETTER AT HIGHER RPMS (I USED TO BELIEVE THIS BUT NO MORE).

Here is a crude example below:

The scratch tool is a piece of 1/32 ID brass tubing with a 1/32 piano wire sharpened to a needle point (hobby shop stuff) . The brass tubing is taped to a heavy steel block and the block mounted on something solid like a car jack or a stack of bricks. The needle should not extend more than 1/8" from the brass tube or the steel block or it will flex and not give a accurate reading. The opposite end of the wire should extend out of the brass tube so you can push it at the right moment. A piece of polished steel sheet metal is taped to the timing cover NEAR THE AXIS CENTER-LINE OF THE CRANKSHAFT (not on the frame).

The P11 thread


Start the bike, hold the front brake.

Rev it the the RPM you want to test (4000 or 6000 etc) and have a helper tap the end of the wire as quickly as possible against the sheet metal. Move the bike forward 1/2 inch and repeat the process.

This test is very difficult to get right and it needs refining. I could only get a good witness mark about 2 times out of 10 tries. And you have to have a microscope to see the elliptical scratch clearly. It was not possible to get a good photograph so I drew an image (below) of the scratch test of my featherbed with a 72% wet balance factor with JS lightweight pistons & longer rods. The ellipse measured about .020" or so in dimension. It will probably measure a lot more in an isolastic frame or in any bike with heavy stock pistons. As you can see the 72% is too high because the motor shakes horizontally more than vertically at 6000RPM. A lower balance factor would shake less horizontally but more vertically. More tests need to be made and a good time to do it is when the bike is on the Dyno with various frames - isolastics etc. I'm guessing that tests will show the best BFs will be in the 60 to 70% range. Note that 65% wet BF(accounting for oil in the crank) = about 72% dry BF

The P11 thread
 
P400 is asking about balance info for JS lightweight pistons in solid frames - see specs below.

The specs on top are for the ultralight rods that I recommend for all solid framed 750s
The specs on the bottom or for my regular rods which are good for motors up to 1000cc

Norton 750 balance (wet) lightweight pist & JS Carrilllo ULTRALIGHT bushless rods
A wet balance factor of 65% equals a dry balance factor of 72%
piston 185
rings 18
pin 51
rod PE 95
reciprocating one side 349
reciprocating total 698

big end w bolts 307
big end shells 43
crank oil for one side only 25 (about 28 for Maney crank)
big end one side 375
big end total 750



reciprocating x 65% 453.7
Plus rotating = bob wt 1203.7 Wet bob weight



******************************************************************************************

750 Norton Balance (wet) JS lightweight pist &rods
A wet balance factor of 65% equals a dry balance factor of 72%
JS/ regular Carrilllo bushless rods
piston 185
rings 18
pin 51
rod PE 105
reciprocating one side 359
reciprocating total 718

big end w bolts average 326
big end shells 43
crank oil for one side only 25
big end one side 394
big end total 788


reciprocating x 65% 466.7
Plus rotating = bob wt 1254.7 wet bob weight
 
I am trying document what an original P11 balance factor appears to be. And this must be the same for pre Commando 750. and maybe same for early 68-70 Commandos.
P11 original balance numbers in grams
original piston 220
original rings 18
original pin 70
original rod Pin End 130
reciprocating one side - 438
reciprocating total - 438 x 2 - 876 grams
--------------------------------------------------
big end bolts shells 320
big end one side 320
big end total - 320 x 2 - 640 grams
So I modified a wheel truing stand to accept a P11 crank resting on ball bearings
I put the piston pins back in for holding a bolt in each....and starting adding big steel washers .
I want to back calculate the balance factor.
The rough weight required to counter this assembly as shown is roughly 530grams
530 is the total weight of pins, bolts and steel washers.
Please do the math and tell me what you find for balance factor!
Do these numbers make sense?
How do I get a "bob weight"?................I figured the "bob" to be everything hanging on the crank to balance it out, two dry rods + 530.
-----------------------------------------------------------------------------------------------
530(measured with this rig) + two complete rods(900dry)=1430 bob weight?
1430 - 640(dry big ends) = 790
790/876 = 90% dry balance factor
YES !!!?

Tens of thousands of Norton and anyone measure this data before?
The same crank listed for all 750 pre Commandos must share this same bob weight, piston weight, rod weight, etc.!
P11, Atlas, N15CS, P11A, G15SR, G15 mk11, etc.
WTF!
 
Still not entirely sure about your weight calculation of the bits hanging down there.
Just clarify for us where the small end weight of the rods is added to ?

I've gone back to thinking/wondering that 60% is the correct calc.
You lay out the data differently to the back-of-the-envelope method...
 
p400 said:
Tens of thousands of Norton and anyone measure this data before?
The same crank listed for all 750 pre Commandos must share this same bob weight, piston weight, rod weight, etc.!
P11, Atlas, N15CS, P11A, G15SR, G15 mk11, etc.

I've not seen anyone ever quote the weights of those concave head pistons before,
after asking here and elsewhere - for a long time.
And the pistons are long gone and not available.

Most folks just bolt on new pistons and go.
I did that (to Commando) and it worked out well.
But the new OS pistons were very close in weight to the old ones.
 
Rohan said:
p400 said:
Tens of thousands of Norton and anyone measure this data before?The same crank listed for all 750 pre Commandos must share this same bob weight, piston weight, rod weight, etc.!P11, Atlas, N15CS, P11A, G15SR, G15 mk11, etc.
I've not seen anyone ever quote the weights of those concave head pistons before,

Hopefully I am not quoting the weight, the point was to show the exact weights.
I cannot understand the discussions on Norton balance factors without all the data.
I don't want a balance shop discussion, or balance factor, or new/old bob weight......simply requesting the start stock weight of Atlas 750/P11 crankshafts.
I am recognizing the response/readership to other Nortons forum is quite low.
 
What is the sprocket set on a P11?
5000rpm equals 87mph? mistake?
My P11 registers 70mph at 5000. bad speedo? bad tach?
 

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p400 said:
Hopefully I am not quoting the weight, the point was to show the exact weights.

?? What distinction are you making here,
you have lost us.

p400 said:
I don't want a balance shop discussion, or balance factor, or new/old bob weight......simply requesting the start stock weight of Atlas 750/P11 crankshafts.

May we ask why then ??
My crank LOOKS stock, I don't give a hoot what weight it actually measures at.
This current branch line of discussion started with your numbers re balance factors of your engine, after all.
 
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