Norton valve and pushrod lengths

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Charles

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Mar 12, 2014
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Having put together a 650 Norton with new valves, seats, springs and pushrods I have experienced problems with excessive wear across the stem tips. I suspect, I could have the wrong combination of pre and post 1968 components? However, I'm experiencing difficultly finding a reliable source of information as to the actual lengths of these components. I would be extremely grateful if somebody with access to pre and post 1968 valves and pushrods together with a vernier caliper could possibly help?
I've read the length was increased on the valve stem and shortened on the pushrods, by 0.1 inch. But as to the original lengths I have no clue? Once I have this basic information I can begin to check the cylinder head geometry.
 
welcome to the forum Charles, sometimes its advisable to check other threads that may answer your problems, please check the thread on pushrods and valves posted 2 days ago in Other Classic Motorcycles.
 
Commando pushrods are 0.060" shorter than the 650SS.

I can't give an accurate answer to the overall length, but ruler says inlet 8 3/16", ex 7 3/8" for the 650 rods

Norton valve and pushrod lengths
 
B+Bogus said:
Commando pushrods are 0.060" shorter than the 650SS.]
Click to expand...

This is bad information because it is usually not the size of the engine that determines the length of pushrod the factory installed, it is the date the machine was manufactured. All 650/750 and 850 machines after a certain engine number used the same pushrods and valves, and all 650/750 machines before that date used common pushrods and valves also. The only exception in the parts book is the 500cc twin, which year for year had a shorter cylinder and pushrods to match.
 
71Roadster said:
B+Bogus said:
Commando pushrods are 0.060" shorter than the 650SS.]
Click to expand...

This is bad information because it is usually not the size of the engine that determines the length of pushrod the factory installed, it is the date the machine was manufactured. All 650/750 and 850 machines after a certain engine number used the same pushrods and valves, and all 650/750 machines before that date used common pushrods and valves also. The only exception in the parts book is the 500cc twin, which year for year had a shorter cylinder and pushrods to match.
Click to expand...

I'd like you to qualify your statement, please?
The Certain engine number in question is 125871, which places it in the 1968 production year.
I rather feel that I'm being called a liar...
 
I don't know exactly what you mean about qualifying a statement. All you have to do is look in the parts books to see that Norton dealers would have sold the same pushrods to the owner of a late 650 as they would a 750 or Commando owner.
Parts and owner's manuals did the job for the Norton dealers and riders back in the day, and usually they still work very good for the purpose they were made for.
 
71Roadster said:
I don't know exactly what you mean about qualifying a statement. All you have to do is look in the parts books to see that Norton dealers would have sold the same pushrods to the owner of a late 650 as they would a 750 or Commando owner.
Parts and owner's manuals did the job for the Norton dealers and riders back in the day, and usually they still work very good for the purpose they were made for.
Click to expand...

In simplistic terms, you've accused me of posting 'bad information', when I was answering the OP's question using relevant parts in my possession.

My information is accurate, posted in good faith and based on actual components.
If the OP's 650 engine number lies after 125871 you may have a point, but I really think this unlikely, as the he has already identified that the anomalies he has lie with pre and post '68 components.
He was asking what the difference was and I answered the question.

If you believe the parts book to be gospel, and better than the evidence of your own eyes, then good luck to you. It still won't answer the OP's question though.
 
B+Bogus said:
My information is accurate, posted in good faith and based on actual components.
If the OP's 650 engine number lies after 125871 you may have a point, but I really think this unlikely, as the he has
If you believe the parts book to be gospel, and better than the evidence of your own eyes, then good luck to you. It still won't answer the OP's question though.
Click to expand...

The factory specs for the pushrod lengths were quoted by "lsrken" in another post a few days earlier:

"Factory spec for Commando pushrods is 8.166/8.130” inlet and 7.321/7.285” exhaust.
For Atlas and P11 intake is 8.194" and exhaust is 7.351".

What LSRKen actually posted was the factory specs for pushrods post engine #12871 and pre- #123871, so him saying that the Commando and Atlas/P11 having different lengths was as bad a bit of information as Bogus saying that 650cc and Commando pushrods were different lenghts.

Anyone can look in early 60s, 1968 parts books, and 850 Commando parts books and see what a dealer would have sold a customer back when the bikes were new, and it was one part number for the 99ss/650/750 engines pre #125871 and another part number post #125871 all the way into 850 Commando production.

Notice the spread of dimensions Ken quotes for the Commando, the difference closely matches the .040" that the Combat head was milled, but he did not say if that was the reason for it. IF the shorter Commando figure is for the Combat then you can see that there is only .030" (1/32") difference between the longer Commando spec and the shorter pre-68' pushrods, which means that with the manufacturing variables and quality between the old original and worn parts laying around and the various people now making valves, replacement seats, lifters and pushrods, you can go ahead and buy a set of new or used pushrods and valves, but betting on them fitting and working 100% as they are supposed to is a crap-shoot and is why you can only order what the parts book says you are supposed to then make sure they do work right anyway.

If you don't trust the books and manuals dealers used for two or more decades, then you should not trust parts taken out of an old engine that anyone could have swapped different parts into over the last 50 years, and the information that needs to be cross-checked more than any other is that from random people you don't know bleating on internet forums, including mine.
 
71Roadster said:
The factory specs for the pushrod lengths were quoted by "lsrken" in another post a few days earlier:

"Factory spec for Commando pushrods is 8.166/8.130” inlet and 7.321/7.285” exhaust.
For Atlas and P11 intake is 8.194" and exhaust is 7.351".

What LSRKen actually posted was the factory specs for pushrods post engine #12871 and pre- #123871, so him saying that the Commando and Atlas/P11 having different lengths was as bad a bit of information as Bogus saying that 650cc and Commando pushrods were different lenghts.

Anyone can look in early 60s, 1968 parts books, and 850 Commando parts books and see what a dealer would have sold a customer back when the bikes were new, and it was one part number for the 99ss/650/750 engines pre #125871 and another part number post #125871 all the way into 850 Commando production.

Notice the spread of dimensions Ken quotes for the Commando, the difference closely matches the .040" that the Combat head was milled, but he did not say if that was the reason for it. IF the shorter Commando figure is for the Combat then you can see that there is only .030" (1/32") difference between the longer Commando spec and the shorter pre-68' pushrods, which means that with the manufacturing variables and quality between the old original and worn parts laying around and the various people now making valves, replacement seats, lifters and pushrods, you can go ahead and buy a set of new or used pushrods and valves, but betting on them fitting and working 100% as they are supposed to is a crap-shoot and is why you can only order what the parts book says you are supposed to then make sure they do work right anyway.

If you don't trust the books and manuals dealers used for two or more decades, then you should not trust parts taken out of an old engine that anyone could have swapped different parts into over the last 50 years, and the information that needs to be cross-checked more than any other is that from random people you don't know bleating on internet forums, including mine.
Click to expand...

So what part numbers are correct for a Combat motor? (I already know the answer, BTW)
How do the parts books help answer the OP's question?
Sorry if I'm just another 'random person', and I'm sorry if you find the information untrustworthy.
I'm also sorry if you think I'm bleating, I was just trying to answer a question... :roll:

Some UK comedy character would be saying 'that's nice' right now. That one will just have to stay with the UK viewers.
 
71Roadster said:
Notice the spread of dimensions Ken quotes for the Commando, the difference closely matches the .040" that the Combat head was milled, but he did not say if that was the reason for it. IF the shorter Commando figure is for the Combat then you can see that there is only .030" (1/32") difference between the longer Commando spec and the shorter pre-68' pushrods, which means that with the manufacturing variables and quality between the old original and worn parts laying around and the various people now making valves, replacement seats, lifters and pushrods, you can go ahead and buy a set of new or used pushrods and valves, but betting on them fitting and working 100% as they are supposed to is a crap-shoot and is why you can only order what the parts book says you are supposed to then make sure they do work right anyway.
Click to expand...

I don't think that the tolerance in the pushrod length specs has anything to do with the Combat differences. I took the specs I posted for Commando pushrod lengths on the other thread from the factory Commando service manuals, but I've also measured a fair number of stock pushrods, and they tend to be in the middle of the spec lengths, with a spread of plus or minus .010". I think the variation is just the level of precision to which the factory manufactured them.

FWIW, I took the lengths for the Atlas pushrods in the other thread from the specs in a Norton and Hybrids 1966-1976 Service Manual on Kim the CD Man's Norton CD. I suspect it is not a factory manual, but one of the aftermarket published manuals. Information about who published it has been removed from the copy on the CD. You are quite right about what the parts books say regarding engine numbers and pushrods, so I suppose it's possible that there are Atlas engines out there that came with the later length pushrods, as unlikely as that might seem. There have been documented P11A Rangers with serial numbers higher that 125871, so I suppose there might also have been some Atlas in that range. I've not measured any pushrods from pre-Commando models, so don't know how much they might vary.

Ken
 
650 750 and 850 barrel height and I think the 600 also are the same.
The push rod length most likely only changed due to valve length change...combat was not a different push rod.

The combat had a .040 cut head yes....but also a high lift cam with .059 more lift.
I take 1/2 of the head cut and 1/2 of the cam change and you get about .050..... IMO that is how much a combat push rod should be reduced to be in a better ballpark than the later post 12???? to 75 push rods.

If you are going to higher lift cam, than combat, you might need norvils 0679501 which are .090 shorter
 
dynodave said:
650 750 and 850 barrel height and I think the 600 also are the same.
The push rod length most likely only changed due to valve length change...combat was not a different push rod.

The combat had a .040 cut head yes....but also a high lift cam with .059 more lift.
I take 1/2 of the head cut and 1/2 of the cam change and you get about .050..... IMO that is how much a combat push rod should be reduced to be in a better ballpark than the later post 12???? to 75 push rods.

If you are going to higher lift cam, than combat, you might need norvils 0679501 which are .090 shorter
Click to expand...

When I put my Combat together I found by experiment that removing 0.060" from the pushrods brought the rockers back in line, so we're in the same ball-park. I'm sure 0.050" would work.

I note that A-N give Commando push-rod lengths as 8.15" and 7.3" (compared to my 'best endeavours' of 8.1875 and 7.375 for the 650SS (mine's a '64) )
 
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