Norton 750 and 820 barrels and quality control.

......or KWOLYTI Control as I often addressed my reports during my working life in the British defence industry......it was a dig at the company having no quality control worth speaking about ......
Barrels were on occasion manufactured and fitted with the top face not parallel with the base flange and sometimes with bores not parallel to each other. For example I once took a only very slightly worn 88 barrel and shoved it on a set of minus rings pistons to check things....one piston would move a few though in all directions but the other sould not....thinking bent rods I changed the rods over which had no effect....then I checked the distance between the bores top and bottom and found 5 thou difference. One bore was not parallel with the other and talking to friends with many decades of Norton experience I was told this was not unknown.....
Now some people when boring Norton barrels clamp them down on their top face...its easier than sorting out a few perfectly matched spacers to hold then down on their base flange.....trouble is that if the top flange is not parallel with the base flange then the new bores are not correct with respect to the crank......One friend when rebuilding motors for customers always checks the barrel has been correctly machined initially / rebored but I dioubt many other so called experts do so..... A few minutes ago I learnt that some people bore barrels with el cheapo boring machines that fit on to the top face so if the top face is incorrect......
As for some of the piston and ring sets available these days I thank the gods I have genuine ones in stock. The tales I hear from friends in the trade...... ever seen for example those CRAPPY ******* Commandeo clutch friction plates made in some back street shed somewhere in either India or China for example?? Not only are they semi flexible but the teeth come no where near fitting the involute spline on the clutch centre (a rare CORRECTLY splined one that is!!) but the shear strength of the friction material is around 2,000 lb per sq inch while the original Don 112 solid asbestos based ones had a shear strength of 9,000 lb per sq inch. Wonder how long theteeth stay on the plates in use??? Apparently one major Norton dealer upon being shown a set instantly banned then from his shop! I should add I still have one still in its original ******* packaging. A certain University Mech Eng Dept did the shear testing for me and e mailed me the graph showing the results.....No point in having frioends in charge of such establishments if you donr get them to do something more useful than turning out lots of 20 odd year old know less than nothing BSc graduates who dont even know what a chick key looks like or how to use it..... Comment heard for many years now ...'We will be lucky if we turn out one real Engineer from this years student intake'. One Triumph owning friend for example who would rebuild engines and gearboxes for people sold everything Meriden a few years ago simply because he was totally fed up having to modify many new parts so they fitted correctly. He now owns a couple of modern Triumph 'battle tank's...and I laugh as I hear then leave my house as there is an audable CLONK from the gearbox as he drives away changing gear......than the gods my car clutch works correctly!! Apparently the clonk goes away as things heat up.... I assume they included a tad of Triumph clutch drag to satisfy the ex Meriden Triumph owners! Wonder if rocker covers come off as one goes down the road?? One road tester reported something like ..' I was quickly reminded I was riding a Triumph as a rocker cover overtook me........' another said ...' As with the last Triumph tesated it was possible to start the engine with the clutch lever back to the bar.........' Some road tests, NOT MANY mind you, told the truth.

I remember reading somewhere that a lot of 850 barrels had a fairly consistent 6 thou difference from side to side because the top of the barrels were not parallel with the base.

Maybe the stick wasn't available that day.

Hi, that's what I have been told ,in 1974, when I bought my first new 850 Commando, by a well known french Triumph dealer, who dismantled the engine and bored back the barrel plus 0.010....

Well, that'll explain why I can't get my squish gap even at all measuring points!

So, if the barrels were of questionable dimensional consistency, it begs the question, can we rest easy the CASES were done well? Or is a full dimensional/geometric inspection warranted there as well?

Hi, some 25 years later (so in 2000), I had met an engineer , who had made an aligning mandrel to fit into the cases , without putting the bolts (and dowells) , but holding them (do not ask me more , as my english is poor.....! as my engineering knowledge!), to make sure the bearing holes were concentric, and then he could slightly mill the top of the crancases, so making sure they were flat and perpendicular to the axis of the crankshaft, or on another way , I had been told to ease the dowel pin holes , not tighten the bolts, then put the barrel on the cases (and tighten the nuts and the through bolts for the 850), then only tighten the fixing bolts of the cases , but as you had noticed you could make so far a slight discrepancy in the level of the two cases , better you had previously put some nice compound on the face of them (hylomar , gasgasinch or yamabond!!), but the first approach seems more technical ........phew!

When I sent my barrels down to Phil for oversize boring and new pistons, etc., he found the top and bottom surfaces were not even close to parallel.
They had to be machined well into the "raised" area, to make them right. Something I had never even considered...

I wonder how many of you saw as I did the ex Norton barrel boring jig in use boring piles of new barrels at a certain family run company in Birmingham shortly after NVT went to the wall? The jig was probably very accurate in 1947 when boring Mod 77 barrels .........New overbored barrels requiring reboring to +10 or +20 were very cheap for cash.....and new ex Norton stock pistons were a LOT cheaper....happy days!!

J. M. Leadbeater said:

I wonder how many of you saw as I did the ex Norton barrel boring jig in use boring piles of new barrels at a certain family run company in Birmingham shortly after NVT went to the wall? The jig was probably very accurate in 1947 when boring Mod 77 barrels .........New overbored barrels requiring reboring to +10 or +20 were very cheap for cash.....and new ex Norton stock pistons were a LOT cheaper....happy days!!

Click to expand...

What's it matter now?

Anyone who has got to this level of parts examination realizes that Norton parts are not made on the space station, nor made to strict design specifications. Given the manufacturing environment back in the day was perfection possible/affordable?? Someone once told me that BSAs were better machines because they were made below ground level where the environmental temperature varied less??

In the example illuminated by J. M. Leadbeater where the bores where out of parallel by .005, or the other example of cylinders having out of parallel head/case surfaces (with the extreme exception caught and repaired by Radford). I'm curious as to what is a reasonable tolerance? And what could one expect if all surfaces were correctly parallel/perpendicular? With a skirt clearance of .0045 for cast pistons and a .0055 for forged, is .005 out-of-parallel set of bores really significant??

Auto makers during the Norton years where making engine blocks on machines that varied tolerances between cold start-up to hot shutdown by much larger figures and still could go over 100,000 miles before giving up the ghost.

My sense is that if you want a motorcycle with tolerances closer to perfection you need to purchase considerably more modern examples. To me that draw of antique British motorcycles are their abundance of "perfect imperfections"...

Parallel is one thing one, I'd expect 0.0005'' these days as the norm. Parallel and square to the bores in the 60's & 70's I some how doubt was even achievable to a satisfactory standard then with the worn out tools being used.

I remember talking to the local Norton dealer in Mesa AZ back in the 70's. He told me of a new set of cylinders for a 650 he had gotten from Norton that had a casting flaw in them. Had a hold in the cylinder wall you could see the combustion flame come out between the fins. So much for quality control.
At the same time I worked for a Ford dealer that had a new truck in for warranty service. Oil in the coolant! Turned out that there was a casting flaw in the block that allowed oil into the water jacket. Ford sent us a bare block but the customer was never happy and quickly traded it in on a GMC. Can't blame him.

John in Texas

" is .005 out-of-parallel set of bores really significant??"

Yes.