Piston Pocketing

worntorn said:
I have no opinion on the VIP choice. As Jerry says, it's OK either way.
Maybe 74ok forgot to renew. It's easy enough to do.
It was just a chuckle, the Post and the no VIP status :)

Glen
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Yeah that slip in the post was kind of funny.

Greg told me I have no purpose for being here and posting as much as I have. So I joined up VIP looking for a purpose. That didn't work either. I'll just stick with being a douchebag when my membership needs renewal. :)
 
dobba99 said:
Sell the 2S, buy a standard cam and have a more flexible, tractable engine that will be nicer to ride. Dealers will sell you anything including performance cams along with the words like 'best road cam ever' to quote Mick Hemmings. The one thing dealers won't do is ask you how you ride and what are you going to use the bike for. Instead of 'best road cam ever' they should ask 'Are you going to ride around at WOT? if so, you need a 2S, 4S, PW3 etc cam' They will let you cope with all the fallout from using said cams and by fall out i mean all the extra work to do to the engine to get it to run safely. The higher lift cams WILL give the valve gear a harder time and be noisier. The horse power might be a little better at the top end but the payoff is the crap bottom end grunt.
Just to get the C.R. back to something like where you want AFTER you have pocketed the pistons will mean shaving the head, or deleting the head gasket or a mixture of both.
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The 2S cam works great on a road going Commando, I ride mine everywhere, works good down low revs around the suburbs without any problems at all, get it above 4000 RPMs and it will perform better than a standard cam in my opinion, it picks up better when opening the throttle, my 850 runs very smooth with the 2S cam, but then I have my crank balanced at 72%, in fact my motor runs great with the 2S cam, my valve aren't noisy at all when running and my motor runs more freely with the 2S cam, my head was only shaved about 15thu and I run a copper head gasket and a standard base gasket, it has a lot more compression than when it was stock, but the longer kicker and the Joe Hunt magneto makes it a one kick to start every time.
My motor is very reliable and hasn't let me down in the 43+ years I been running a 2S cam, so really my Norton motor hasn't lost any bottom end grunt at all, in fact it has improved it, from putting around at 40 MPH in top gear and if I open the throttle right up it pulls like a train without any hesitation at all, but then with the port work, open exhaust, carbs jetted right and crank balanced all helps this 2S cam to work its best for a road going Commando motor, my gearbox is running the same size front sprocket from the factory, so I haven't changed the gearing at all, a lot of folks on here say running a 2S cam you will lose low down grunt, if the bike and motor is set up right it will improve it.
I have owned my 850 from new (last of the 74 KS model) and I converted it to the Featherbed frame in 1980/82 and when I built the motor for the hard mounts was when I did the 2S cam and all the other work to my motor and my motor performs so much better and more freely than when it was stock, I just love how it performs.
So I think you are going to enjoy running with the 2S cam, it's just the right profile in my opinion for a road going Commando without over doing it, and you will get a lot more revs only because the motor is running more freely as long as you have everything else tuned and working with the cam.
But then what would I know as I only been riding my Norton with this 2S cam and all the other improvement to my 850 for only 43+ years and has been an everyday rider for most of its life averaging between 6k and 10k miles a year and has never let me down motor wise.
By the way it still pulls like a train but it was rebuilt slightly 15 years ago when I had to replace the original crank cases from cracks around the main oil seal and a front broken stud (middle stud, broken piece of the crank case where the stud went in) of the crank case, (that's another story lol).

Ashley
 
ashman said:
The 2S cam works great on a road going Commando, I ride mine everywhere, works good down low revs around the suburbs without any problems at all, get it above 4000 RPMs and it will perform better than a standard cam in my opinion, it picks up better when opening the throttle, my 850 runs very smooth with the 2S cam, but then I have my crank balanced at 72%, in fact my motor runs great with the 2S cam, my valve aren't noisy at all when running and my motor runs more freely with the 2S cam, my head was only shaved about 15thu and I run a copper head gasket and a standard base gasket, it has a lot more compression than when it was stock, but the longer kicker and the Joe Hunt magneto makes it a one kick to start every time.
My motor is very reliable and hasn't let me down in the 43+ years I been running a 2S cam, so really my Norton motor hasn't lost any bottom end grunt at all, in fact it has improved it, from putting around at 40 MPH in top gear and if I open the throttle right up it pulls like a train without any hesitation at all, but then with the port work, open exhaust, carbs jetted right and crank balanced all helps this 2S cam to work its best for a road going Commando motor, my gearbox is running the same size front sprocket from the factory, so I haven't changed the gearing at all, a lot of folks on here say running a 2S cam you will lose low down grunt, if the bike and motor is set up right it will improve it.
I have owned my 850 from new (last of the 74 KS model) and I converted it to the Featherbed frame in 1980/82 and when I built the motor for the hard mounts was when I did the 2S cam and all the other work to my motor and my motor performs so much better and more freely than when it was stock, I just love how it performs.
So I think you are going to enjoy running with the 2S cam, it's just the right profile in my opinion for a road going Commando without over doing it, and you will get a lot more revs only because the motor is running more freely as long as you have everything else tuned and working with the cam.
But then what would I know as I only been riding my Norton with this 2S cam and all the other improvement to my 850 for only 43+ years and has been an everyday rider for most of its life averaging between 6k and 10k miles a year and has never let me down motor wise.
By the way it still pulls like a train but it was rebuilt slightly 15 years ago when I had to replace the original crank cases from cracks around the main oil seal and a front broken stud (middle stud, broken piece of the crank case where the stud went in) of the crank case, (that's another story lol).

Ashley
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I believe the 850 gave more bottom end and perhaps the 2S cam may reduce the bottom end but I'm expecting no less than the STD 750 but it would have more top end than the Combat and an 850 - sounds alright to me! But lets not digress about this as my question is about the pocketing of the pistons 👍
 
When I built my Seeley 850, it did not matter to me what the cam was. I had it reground by a guy who had ground good cams for bikes over many years. I am fairly certain the grind is 650ss. My cam sprochet has two more keyways ground into it at random, so I get finer adjustment on the cam timing. Getting the best out of a cam by adjusting the timing, depends on the inlet tract and the exhaust system. I use 12 degrees advance ahead of normal with a two into one exhaust system, Consequentlymy exhaust valve opening point is about 92 degrees BBDC, and my inlet valve opens a 65 degrees BTDC. The power band is between 5000 and 7000 RPM, and I get smooth power delivery everywhere.
It is common practice after adjusting valve timing - to place a small piece of kid's play-dough in the valve cutaways and rotate the motor. When you section the play-dough with a razor blade, you can see how much clearance you have.
I normally set the valve timing from experience about the exhaust system I use, and adjust everything else to suit it.
Where the power band ends-up and your intended use for the bike - determines gearing, and also carb jetting.
You can make your bike go faster with high revs, or pull harder with low revs, wherever you might choose. It is difficult to get both power characteristics, without making changes to the set-up.
If I race, I never worry about the time it takes me to reach full thottle. I feed the throttle on slowly and race-change the gears. The bike is much quicker when the carb needles are in use, than when it is suddenly exposed to full throttle. Suddenly richening the mixture makes the motor slower.
 
Time Warp said:
After reading some of the tripe in this thread I have now cancelled my Paypal auto payment for the website monetary contribution in the form of the VIP which is hardly about status.

What a bunch of silly old men.

Its such a disappointment (not the first time) Admin feel free to remove the VIP Member from my my profile.


"VIP Member (Annually)$39.00 per 12 months
Expires: Jul 22, 2025
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I know I am silly, but it makes me happy. Most idiots do not have my mindset. When you lose interest in living, you are dead. I have been given a new option by my wife. I am allowed to race again, but I have to die if I crash. - I do not know what to do with that.
 
marshg246 said:
On a 750 Combat, with the pistons in backwards, the valves lightly kiss the pistons (built by dummy - brought to me due to the weird noise). You don't need anything near the full pockets on a 750 so I doubt that you do on an 850. A Combat has .040" skimmed from the head. The diameter of the valve can be much more than the cut out is wide. Distance from the edge is more important.

I wouldn't do it at all, but since you insist, put it together, find out exactly where the valves hit, if they do, and make a small cut to accommodate, keeping in mind that if you over-rev, the valves might float, and you'll need more clearance. If both the intake and exhaust hit, you'll notice that the distance from the edge of the piston is different.

IMHO, you must get to 10:1 compression or better for 2S cams.
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Some early race cams were valve-droppers. You are probably better-off with something which has been widely used such as the 65OSS cam or something which was proved to be good in the mid-1970s. All this stuff about throttle position is pretty irrelevant. Whatever cam you have, you can make work effectively. Do not expect to change just one thing and automatically have a better bike. Everything on a motorcycle interacts. It takes experience to know when you need a jetting or gearing change. That is the difference between fast and slow.
 
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acotrel said:
Some early race cams were valve-droppers. You are probably better-off with something which has been widely used such as the 65OSS cam or something which was proved to be good in the mid-1970s. All this stuff about throttle position is pretty irrelevant. Whatever cam you have, you can make work effectively. Do not expect to change just one thing and automatically have a better bike. Everything on a motorcycle interacts. It takes experience to know when you need a jetting or gearing change. That is the difference between fast and slow.
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Have no clue why you chose to reply to me and then be captain obvious!

Don't get how you think riding fast or slow is irrelevant to cam selection, compression ratio, front sprocket selection or any of the other things I've said.

You may be God's gift to race tuning, but a VERY LARGE percentage of the members here consider that to be irrelevant to our interest in old bikes!

I bet you're one of a tiny group that would consider a 650SS cam for a Commando, and the standard cam to not be proven in the 1970s!
 
Nourish said:
In the Norton Service Sheet N3 56 there is a dimensional drawing to modify the pistons for fitting a 2S cam. The drawing dimension for the two pistons pockets is 0.718" radius - that'll be 1.436" diameter. The Inlet valve is 1.490" diameter and so is the valve likely to clout the piston - and can the exhaust cut away be smaller?
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In case you don't know, N3/73 supersedes N3/56
 
marshg246 said:
Have no clue why you chose to reply to me and then be captain obvious!

Don't get how you think riding fast or slow is irrelevant to cam selection, compression ratio, front sprocket selection or any of the other things I've said.

You may be God's gift to race tuning, but a VERY LARGE percentage of the members here consider that to be irrelevant to our interest in old bikes!

I bet you're one of a tiny group that would consider a 650SS cam for a Commando, and the standard cam to not be proven in the 1970s!
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The standard Commando cam is the 650ss profile.
Andover shows the same part number for the 650ss and Atlas as the first three years of Commando. End changes occurred after that but the profile remained that same 650SS profile. (Except Combat and PR bikes)
 
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You know my original post was about creating valve pockets in my pistons - I gave you all too much information! It doesn't matter what cam I've chosen so your opinions don't really matter in this post. As for VIP status - that really has no connection to my post!!
You've all Hi Jacked my conversation😢
 
Nourish said:
You know my original post was about creating valve pockets in my pistons - I gave you all too much information! It doesn't matter what cam I've chosen so your opinions don't really matter in this post. As for VIP status - that really has no connection to my post!!
You've all Hi Jacked my conversation😢
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Try not to worry about it
It's just human nature
 
Nourish said:
You know my original post was about creating valve pockets in my pistons - I gave you all too much information! It doesn't matter what cam I've chosen so your opinions don't really matter in this post. As for VIP status - that really has no connection to my post!!
You've all Hi Jacked my conversation😢
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Your post #8: "Perhaps someone who has the ability to attach images here could do so for me from 'Norton 850 Commando Stage One Perf Mods' up in the 'Resources' tab at the top of this page or just go straight to https://www.accessnorton.com/resources/norton-850-commando-stage-one-perf-mods.15/'

So, VIP status was started by you in this thread whether you knew it or not!

People who pay can upload pictures. You asked for someone who could upload to help you. In other words, you asked someone who pays to be a VIP to upload pictures for you.

The opinions of others never actually matter, but then this is an open forum - just as you have the right to ask, everyone else has the right to answer as they see fit.

That said, it is annoying to get off track and not get you question answered. In this case, your question and your stated misconceptions have been thoroughly answered! If you disagree with that, please tell us what is still confusing,
 
Nourish said:
You know my original post was about creating valve pockets in my pistons - I gave you all too much information! It doesn't matter what cam I've chosen so your opinions don't really matter in this post. As for VIP status - that really has no connection to my post!!
You've all Hi Jacked my conversation😢
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Welcome to Access Norton

The VIP thing is not even close to how far off topic threads get here.

You won't have any trouble installing the 2S cam. The cam tunnel may need to be increased in diameter for lobe clearance. I would imagine all the modification bases have been covered by others somewhere in this thread.

I've never installed a 2S cam in an 850, but have installed a Commando 2S cam in pre-Commando 750 cases. People that have never tried it said that wasn't possible. However it is.
 
Nourish said:
You know my original post was about creating valve pockets in my pistons - I gave you all too much information! It doesn't matter what cam I've chosen so your opinions don't really matter in this post. As for VIP status - that really has no connection to my post!!
You've all Hi Jacked my conversation😢
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Every thread gets hijacked a little by people who want to talk about something else. It can suck when you really want an answer to a certain question and people respond with stories about themselves.... But to stay on track,... Part of the issue with your cam choice is that people don't report their success with a choice nearly as much as they complain about the failure/poor performance of their chosen part. That kind of "fact" skews the searchable threads on a topic towards the bad results.

I always wonder in a case like yours if we had 2 commandos set up exactly the same with the exception of the 2 different cam profiles, if riders could switch back and forth over the course of an afternoon's riding and definitively know which bike had which cam... I would do it a few times and then try a "fake test" where they were told it was 2 different cams,.... but they were actually 2 bikes both with the same cam, to see if their internalized expectation to detect a difference would cause them to guess they were different....

So, without anything of substance to add,.... be careful measuring your piston pockets and report back this summer once your bike is up and running, how you feel about the cam you've chosen. I bet you figure out where it will lug RPM wise, and adjust your shift points to suit the engine performance and eventually not think anything is different than it should be....
 
Schwany said:
Welcome to Access Norton

The VIP thing is not even close to how far off topic threads get here.

You won't have any trouble installing the 2S cam. The cam tunnel may need to be increased in diameter for lobe clearance. I would imagine all the modification bases have been covered by others somewhere in this thread.

I've never installed a 2S cam in an 850, but have installed a Commando 2S cam in pre-Commando 750 cases. People that have never tried it said that wasn't possible. However it is.
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The 2S cam is in - and it's staying but the valves are hitting the pistons!!!
 
Nourish said:
The 2S cam is in - and it's staying but the valves are hitting the pistons!!!
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Not enough info for anyone to say much.

Base gasket?
Head gasket?
Rocker gap?
Head shaved?
How hard are the hitting (stopping the engine from turning, just touching, marking the pistons, etc.?)
 
Methinks Greg that was enough - too much in hindsight - info as the question was about the diameter of the valve cut outs required.
 
Nourish said:
Methinks Greg that was enough - too much in hindsight - info as the question was about the diameter of the valve cut outs required.
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Wrong! No one can tell you the diameter without knowing such things. Of course, you already knew the "book" answer so there was no reason to ask a bunch of street riders/builders how to do what you are doing! No hindsight involved - only forward trying to help. No problem though - you have zero respect for people trying to help you so I'm out.
 
Hi did you use a vernier sprocket to time the camshaft , and if not how far are you from the traditionnal ten pins between dots ?
 
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