P11 loose steering head

I spoke with Mike Patrick a few times about some of the many modifications he made to keep 121013 out front. It was always a work in progress. There were many repairs made to the continually cracking frame because of the engine mass. He also said that the Teledraulics were inadequate for him and quickly changed over to the long Norton Roadholders as fitted to the early Atlas scrambler, N15's & G15's. He said that his P11 was his only racer that never threw him over the bars. I also asked him about the feeble way the front brake torque arm was attached to the left hand lower slider by the 1/4" fender mounting studs. The alloy was breaking away at the mounting holes. He said he stopped racing it before it was a problem and he didn't use much brake anyway with engine compression and light braking with the rear brake being sufficient. There were so many modifications made to that racer it would be a whole new thread to list them all. Maybe I'll start that thread one day? Right now I'm too busy getting ready to take a couple of 50 year old Norton's on a trailer pulled by a 25 year old mini RV on a 2 thousand mile round trip to the INOA rally and catching up with my wife's Seattle family. What could go wrong?

mdt-son said:

Teledraulic forks were used in heavy 500cc scrambles in the 50's and 60's including jumps and hard landings with no ill effect as far as I know. P11s were entered in scrambles events as well.
However, I just discovered that Mike Patrick's old race bike was retrofitted with Roadholder sliders, so maybe his forks did suffer from slider cracks. We will probably never know.

The alloy is now 50+ years old and it will be affected by fatigue.
Ideally, oil pressure on the compression stroke affects the bottom of the slider only, but with a worn slider and bottom bush 021495, compressed oil will leak by and excert radial pressure on the slider's upper part as well.
http://www.rocbo.net/technique/norton_workshop/103.html

In addition, there is the mechanical load trying to bend the slider, but that load will not generate hoop stress cracking as seen in the picture above.

-Knut

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jerrykap said:

Right now I'm too busy getting ready to take a couple of 50 year old Norton's on a trailer pulled by a 25 year old mini RV on a 2 thousand mile round trip to the INOA rally and catching up with my wife's Seattle family. What could go wrong?

Click to expand...

Hopefully nothing, just stay awake. Enjoy your holiday, Jerry!

-Knut

I know Matchless and P11 fork legs/stanchions/spacers are all the same. What about the steering head yokes (triple trees)? I had heard somewhere that P11 are unique. What is different about them?

I

elefantrider said:

I know Matchless and P11 fork legs/stanchions/spacers are all the same. What about the steering head yokes (triple trees)? I had heard somewhere that P11 are unique. What is different about them?

Click to expand...

I can see a stock P11 yokes and a 1963 Matchless one.
Are absolutly the same.
Ciao
Piero

thanks Piero.

Has anyone tried these shrouds on ebay? They look thicker, more robust than stock.

https://www.ebay.com/itm/Norton-P11...-STAINLESS-matchless-g85-02-8051/162990560716

My stock ones are dented. I prefer chrome (do not like stainless on this bike) but cannot find good used chrome originals. Most are dented.

pierodn said:

I can see a stock P11 yokes and a 1963 Matchless one. Are absolutly the same.

Click to expand...

Piero, why would the factory assign a new part number to the P11 yokes if they were the same as the 1960-63 version? That doesn't make sense. AMC re-used old parts wherever possible. When a new version or some detail change occured, the part became a new part number - logically. The 1963 G80 roadster conrod for instance still carried the part number assigned in 1950 ..... and so on.
Besides, the G85 steering head geometry differs from the roadsters, AFAIK. If the factory didn't alter it, then the yokes had to be machined differently to the 1963 roadsters as well in order to achieve the desired trail (probably the same as the G80CS). The trail would be different, as the 1963 roadster models had an 18" front wheel, the G80/85CS however a 21in wheel. Take a look at pictures showing the side view and you will see what I mean.

Too much trail makes a motorcycle stable but difficult to turn; too little makes it unstable. I vaguely remember the tester's verdict of the G85CS as being slow in turning, which isn't surprising at all given the large trail. The P11 needed quicker steering for road use, and a 19" front wheel was fitted.

Thus, if you compared these yokes by viewing only, your statement is invalid. Have you measured the stanchion to head stem angle accurately, preferably in a coordinate measuring meachine? The difference in frame castor angle may be as little as 1 degree. You can't see it with your naked eye.

elefantrider said:

thanks Piero.

Has anyone tried these shrouds on ebay? They look thicker, more robust than stock.

Click to expand...

I have them (not yet fitted). The cylinder is turned, not rolled. They are definately thicker than the stock ones. A little crude in my opinion, but probably acceptable to most people. The threaded section to cylinder joint should have been better made (brazed) in my opinion. Whether the thicker cylindrical part is an advantage I don't know. In case of an impact to the shrouds (actually they are slider extensions) I prefer them getting dented, to the slider being damaged as threads are ripped out.

-Knut

mdt-son said:

Piero, why would the factory assign a new part number to the P11 yokes if they were the same as the 1960-63 version? That doesn't make sense. AMC re-used old parts wherever possible. When a new version or some detail change occured, the part became a new part number - logically. The 1963 G80 roadster conrod for instance still carried the part number assigned in 1950 ..... and so on.
Besides, the G85 steering head geometry differs from the roadsters, AFAIK. If the factory didn't alter it, then the yokes had to be machined differently to the 1963 roadsters as well in order to achieve the desired trail (probably the same as the G80CS). The trail would be different, as the 1963 roadster models had an 18" front wheel, the G80/85CS however a 21in wheel. Take a look at pictures showing the side view and you will see what I mean.

Thus, if you compared these yokes by viewing only, your statement is invalid. Have you measured the stanchion to head stem angle accurately, preferably in a coordinate measuring meachine? The difference in frame castor angle may be as little as 1 degree. You can't see it with your naked eye.

Click to expand...

You are right.
But they seems the same.
Only two differences you can see:
1. Bottom yoke has the two long hears (right and left) for stop the angle of turn;
2.Top yoke has two holes, one for each side, may be for cable or wires.
Same stem angle, same weight, same high, same!
Ciao
Piero

pierodn said:

Same stem angle, same weight, same high, same!

Click to expand...

By your reply I take it you haven't verified the angle (stem/stanchion) by measurement.

-Knut

mdt-son said:

By your reply I take it you haven't verified the angle (stem/stanchion) by measurement.

-Knut

Click to expand...

Yes yes.
I have verified it with the goniometer of my young son

elefantrider said:

thanks Piero.

Has anyone tried these shrouds on ebay? They look thicker, more robust than stock.

https://www.ebay.com/itm/Norton-P11...-STAINLESS-matchless-g85-02-8051/162990560716

My stock ones are dented. I prefer chrome (do not like stainless on this bike) but cannot find good used chrome originals. Most are dented.

Click to expand...

I have a set of these. They are quite nice. They are maybe slightly thicker than stock, but not nearly as thick as the ones supplied by the Matchless owners club.

Thanks, I did not know the Matchless owners club supplied them. I have never bought parts from them.

pierodn said:

You are right.
But they seems the same.
Only two differences you can see:
1. Bottom yoke has the two long hears (right and left) for stop the angle of turn;
2.Top yoke has two holes, one for each side, may be for cable or wires.
Same stem angle, same weight, same high, same!
Ciao
Piero

Click to expand...

I have found another difference. My top Matchless yoke has an approximately 3/8" threaded hole in it, facing the headlight. The p11 top yoke does not have this hole. What is this hole used for on Matchless bikes?

I have just remembered this hole because I would like to find a way to mount a single gauge like Ekins did, center and more facing the rider:

Here is the hole and bolt on the top yoke of a G80CS yoke. What is this for?

The rest of the yokes look the same as P11.

elefantrider said:

Here is the hole and bolt on the top yoke of a G80CS yoke. What is this for?
The rest of the yokes look the same as P11.

Click to expand...

Speedo bracket. Yes, it looks the same, but I am still not convinced it's identical. AMC could have emplyed the yokes off the 1960-63 G12CS but chose not to.
Why?

-Knut

Well I may use that G80CS top yoke with the Matchless speedo bracket to achieve the speedo mounting I want. Then,if it mates up with the P11 bottom yoke, we will know for sure if they are the same angle. (I think the only difference is the speedo mounting provision)


It looks like the G80CS speedo bracket takes a speedo which mounts with 2 horizontal posts instead of the 2 vertical posts of the P11 gauges.

Still working through that.

Looks like this guy removed the instrument plate but still has his headlamp brackets, just folded in.

Would like to find a higher resolution version of this photo.

Do you need to run the headlamp brackets, if you remove the headlamp?
Maybe they provide rigidity to the yokes?

I see the prototype replica does not have the brackets, so looks like they are not needed after all.

elefantrider said:

Do you need to run the headlamp brackets, if you remove the headlamp?
Maybe they provide rigidity to the yokes?

Click to expand...

In no way do H/L brackets provide rigidity to the yokes, which are solid castings. Their internal distance is determined by headstock and bearings.

As for the G80CS instrument bracket (last version 030404), it's L-shaped and has pillars perpendicular to the console, i.e., almost vertical. AMC Classic Spares may stock them.

-Knut

Thanks mdt-son.

Does the G80CS bracket use vertical screw mount arrangement? The P11 gauges have a vertical arrangement but the G80CS brackets I've seen use a horizontal screw mount. I will email AMC for a photo of their mounts.