The P11 thread

[worntorn]

Are these bikes useable as road bikes, that is beyond a few miles here and there? I have a 650 SS that has enough vibes to stop me from riding it much more than 10-15 miles round trip. I am hopeful that it can be improved with dynamic balancing of the crank, so it is coming apart this winter.
I love the appearance of the P11, but worry that with the solid mounted 750 engine and lightvweight frame, the vibes might turn it into a shop ornament?
It would never be a touring bike, but if vibration was reasonable I could see doing occasional 100 mile days, with a fuel up of that tiny tank in the middle of the run, of course

Glen

 

[BillT]

that 2.5 gallon tank will run an easy 100-110 miles before reserve.

If its got the proper balance factor, P11s are great for almost anything below 70mph, all day long.

 

[worntorn]

So figure 65 as a smooth cruising speed? My 650 is tolerable at 65 but gets pretty buzzy at 70 indicated, which is probably less than a true 70. To keep up with traffic on highways, I find that 70 MPH is needed quite often.
I do try to travel quieter highways as much as possible with the 650SS, but sometimes the 65 MPH Max for cruising just doesn't cut it.

Glen

 

[BillT]

I've done 2-tank days on the Ranger and live to tell about it.

More than that, its my Commando or Speed Triple.

 

[Rohan]

So figure 65 as a smooth cruising speed? My 650 is tolerable at 65 but gets pretty buzzy at 70 indicated, which is probably less than a true 70. To keep up with traffic on highways, I find that 70 MPH is needed quite often.
I do try to travel quieter highways as much as possible with the 650SS, but sometimes the 65 MPH Max for cruising just doesn't cut it.

Have you checked the gearing = counting sprocket teeth.
65 seems a little low for something that was supposed to be good for more than 110+

An alternative to counting teeth is carefully kicking the engine over - in gear - and counting how many engine revs gives so many back wheel rotations.
A chalk mark or similar on the back tire helps, and thumb over the plugholes to count compressions (with plugs removed !).

 

[worntorn]

It runs past the ton quite easily and is still climbing, so I imagine it would do 110 alright, but vibration starts at around 3,000 rpm , then just increases with speed.
The bike is overgeared from stock with a 21 tooth countershaft sprocket as opposed to 19 tooth for stock. It shows a couple of hundred rpm less at 60 MPH than my smooth as glass 850 Commando which also has a 21 tooth cs sprocket. I looked at the two overall ratios in the book and this agrees with what the tachs are showing.
I think I will pull it apart and try a dynamic balance of the crankshaft. If that doesn't do it, then lightweight pistons and rods are the next step, albeit a very expensive one!

Glen

 

[Rohan]

I think I will pull it apart and try a dynamic balance of the crankshaft.

Might be worth investigating what the current balance factor is along the way....

We digress from P11's though, sort of.

 

[BillT]

The stock P11 gearing is also 19 tooth final drive front and 42 tooth rear. Like Norton, the AMC rear sprocket is cast into the brake drum, which is one reason why many racing P11s ran different rear hubs.

 

[Bernhard]

It runs past the ton quite easily and is still climbing, so I imagine it would do 110 alright, but vibration starts at around 3,000 rpm , then just increases with speed.
The bike is overgeared from stock with a 21 tooth countershaft sprocket as opposed to 19 tooth for stock. It shows a couple of hundred rpm less at 60 MPH than my smooth as glass 850 Commando which also has a 21 tooth cs sprocket. I looked at the two overall ratios in the book and this agrees with what the tachs are showing.
I think I will pull it apart and try a dynamic balance of the crankshaft. If that doesn't do it, then lightweight pistons and rods are the next step, albeit a very expensive one! Glen

Re; I think I will pull it apart and try a dynamic balance of the crankshaft. If that doesn't do it, then lightweight pistons and rods are the next step, albeit a very expensive one!

And the very best of luck with that, why do you think Norton’s went and mounted the whole engine/g/box on rubber :?: :idea:
I tried all sorts to cure the vibration on my Atlas, without success :!: :shock:

 

[worntorn]

We all know that neither the 650 nor 750 engines rigidly mounted in a P11 frame or in a Featherbed frame will ever be as smooth as a properly setup Commando, however the 650 is quite a different animal than the 750. Both have the potential to be improved by a two plane dynamic crankshaft balance.
Another reason to look at crank balancing is that in the 1960s Norton decided to stop doing in house balancing and subcontracted this out to the lowest bidder. That man is now known for having randomly drilled a few holes somewhere in each crank without actually going to the trouble of balancing them. Balance factors on untouched Norton cranks built in the 60s are anywhere from 45% to over 90% thanks to this non balancing balancer.

I should ask Bill what methods were used for crank balancing in his P11 type bikes, or did the bottom ends come apart during the restoration?

Glen

 

[Rohan]

Another reason to look at crank balancing is that in the 1960s Norton decided to stop doing in house balancing and subcontracted this out to the lowest bidder. That man is now known for having randomly drilled a few holes somewhere in each crank without actually going to the trouble of balancing them. Balance factors on untouched Norton cranks built in the 60s are anywhere from 45% to over 90% thanks to this non balancing balancer.

We've seen this story mentioned a few times, but is there a source for where this yarn came from ?
All the more reason to measure what your engine's BF is ??

For forged crank cheeks, and a regular shaped and machined flywheel (although cast), you wouldn't imagine there is much scope for the BF to alter much from crank to crank to crank ???
The story I've also seen is that he only sampled every 10th crank (was it ?) to see that they were still within spec.
If every part produced was ABSOLUTELY identical, this is not that unrepeatable.

 

[worntorn]

I was told about the non balancing balancer by the man whom everyone loves to hate, Les Emery.
Agreed that uniform components ought to give a similar balance situation each time, but if someone is drilling random holes, some of which will lighten already too light areas, then things could get pretty far astray.
This is Emery's contention, and he has seen a lot of Norton cranks.
As I recall, he mentioned that the subcontractor was no longer employed by Norton during the Commando years.

Glen

 

[Rohan]

As I recall, he mentioned that the subcontractor was no longer employed by Norton during the Commando years.

What a surprise ?!

Certainly could explain why some owners swear by their Nortons,
and some swear at it...

Let us not forget that Nortons as being discussed here cover 3 almost completely different era's. (?).
Bracebridge St, Plumstead Rd and Wolverhampton/Andover.

 

[Rohan]

but if someone is drilling random holes, some of which will lighten already too light areas, then things could get pretty far astray.

Seems unlikely he would be drilling up anywhere near the crankpin,
unless he was actually testing the balance. ??
And the castings could vary enough that they could be too heavy near the crankpin.

Unless it really was that random.

You'd think that quality control would have looked at the final results, as delivered.
But maybe not, judging by some other accounts of what went on...

 

[hrwat1]

Hi everyone

Plodding on and checking over the bike - some progress made and some mistakes fixed. Just looking at rear side brake plate on rear hub - currently have about a cm between frame and hub - should there be a spacer there or just exposed axle? The reason I noticed is that there is a lot of flex in the rear brake plate when it is activated.

Huw

 

[Rohan]

Definitely a spacer.
Or the swingarm will be bent inwards as you tighten the wheelnuts.
And the wheelbearings etc need to be clamped so they won't rotate.

What does your parts book show ?
G29 Rear brake plate distance piece
is on my list, but not sure what years, or models, it covers.
No dimensions shown either.

 

[p400]

In reply to an earlier request, I was able to climb into the attic this morning and pull down the fender and fender brace I got from a late, P11/125xxx, P11A owner.
Here's the pic:

This pic has the brace clamped in the proper position.
Remember that the P11A seat is several inches longer and the P11A and Ranger used a different tail assembly, requiring more fender length. Also, the P11 front mount is nearly 3" further forward than the P11A.
Holes for the mounts are 1/2" diameter and the bolts are 1/4", leaving room for a grommet. The rub line near the end of the fender is from the license plate.

Bill, Thanks for the great photo. I received info and photos thru the Yahoo group with the following dimensions as well.
The P11A mudguard curvature or depth is notably different with the chrome steel rear.......seems the alloy rear was a "D" profile rather than a "C" profile.
Interesting that the 18" of mudguard was retained and simply rolled back....maybe P11A street use dictated better coverage.
All these P11/P11A rear mudguards appear to be "cut" edge rather than a rolled edge.

 

[BillT]

the four forward holes on that diagram are where the fender mounts to the bike. The three holes at the back are for the aluminum tail light housing - smaller holes to mount, larger hole for the wires. The housing runs pretty close to the rear loop, and the license plate comes just shy of the end, so one needs at least 9 inches for it to fit. The 67 plain bracket sits higher, though some plates may hang over the bottom of the fender

 

[hrwat1]

Managed to dig up a post by Anthony Curzon on the spacer that I mentioned - as far as I can tell it should be PN 028071 and 5/16 x 1 1/4 x 1 3/4.

As a further query, does anyone have the dimensions of the 'collars' that go under and above the headlight brackets? I am just drawing up a diagram to have them made now but thought it worth asking. From the photos I have seen they look like they are alloy to me.

Does the bottom one locate itself on the bottom yoke by slotting over the raised part of the bottom yoke? Is it metal-on-metal? (I was thinking of machining the part on the lathe to allow a rubber 'o-ring' to cushion it - although, if done properly there should be no play).

Huw

 

[p400]

Managed to dig up a post by Anthony Curzon on the spacer that I mentioned - as far as I can tell it should be PN 028071 and 5/16 x 1 1/4 x 1 3/4.
Huw

Can you post a link to the Anthony Curzon post please? Thanks