850 Engine rebuild

so as some of you may have read, first ride out on the Norton this season didn't go very well.
plenty of blue smoke and an engine strip down

turns out the circip left the piston and scored the bore.
having said that it also let me discover another bunch of issues.

so the strip down revealed a lot of silver oil.
it turns out that the front stud had sheared from the casings and unknown to me the piece of alloy has created some bigger issues.

anyway the barrels have cleaned up at 60 thou over so i got myself some new hepolites and some old stock rings to go on them (i don't like the new rings)
the bottom end strip down went ok and everything went surprisingly easily.
initially i thought i would use this opportunity to change the gearbox sprocket, it was a 24 tooth and i plan to drop it down ( after some research) to a 21 tooth, as my riding style isn't so much motorway speed but higher rev country lane riding.

while investigating the bottom end i found the crank to be in reasonably good order but it will probably require a regard to bring it back to spec, I've dropped it into the machine shop and intend to run it with new superblends.

Head wise it apparently was rebuilt by the previous owner. It has been skimmed but i have no idea by how much? is there an easy way to tell??

The camshaft turned out to be a 4S and not the standard cam that i thought it was.
it also appears to be pretty worn and will require replacement.
now this brings me to another question, do i go back to a 4S or should i be looking elsewhere?
Bearing in mind my riding style and country lane riding.

as for the gearbox,
it wasn't wanting to select as easy at it used to and sometimes required and extra tap to place it in gear. any idea what i should be looking for in the strip down??

I highly recommend the PW3 cam from Andover Norton.

Your comment about the gearing interests me. I suggest that if you have a low first gear and the upper three gears are closer, you tolerate a fairly big step from first to second, however you might be better able to use the torque of the 850 motor when you run higher overall gearing. I bought an American 4-speed close ratio gear-set for about $700 a few years ago. It was perfect everywhere except that first gear was too high.

"I highly recommend the PW3 cam from Andover Norton."
suitable for a stock 750 engine?

madass140 said:

"I highly recommend the PW3 cam from Andover Norton."
suitable for a stock 750 engine?

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I know a guy with a 750 Combat and he says it pulls really well with a single Mikuni, especially up around highway speeds. I can't believe what it has added to the 850's repertoire of tricks.

As far as the gear box goes, check all the bushing are in good shape. Some are a sliding fit in the higher gears and need to freely rotate.
At least thats what I discovered when doing my box.
Also the dogs and first gear.

so gearbox has been stripped and rebuild kit added to the growing list, some of the bushes are allowing gears to rock.

i had looked at the PW3 as an option but had also ruled it out because of the modifications required to fit it?

i definitely have a feeling that metal has been the cause of the camshaft wear as the follower has also taken a beating.
where would be the best place to get followers refaced? (in the uk)

Andover Norton would be your best bet for followers in UK. Fitting a PW3 is not beyond the realms of the home mechanic i fitted mine with no problems but many like the stock cam for a street engine but you pays your money so you takes your choice as they say.

Adam_R said:

I definitely have a feeling that metal has been the cause of the camshaft wear as the follower has also taken a beating.
where would be the best place to get followers refaced?

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Would need to see photos to say with more certainty, but the stellite pads on the cam followers can only take so much "beating" (not much) before you need to replace the entire cam followers, rather than waste money attempting to reface them when they will result in too much gap that you will not be able to compensate for at the rocker adjuster end. Also, they should be replaced in matched pairs (although not ultra critical).

These are not bad-



These may be borderline, probably over-



Too much! Here you can see the stellite pad has actually broken.


I've seen some really bad ones, I have a couple on my trash shelf, but couldn't google up an image right quick.

looking at your pictures, i think it may well be a case of "too far gone" i will get pictures tomorrow night. but i think its going to be bad news.

looking very much like another expensive bill heading my way

Thats part of owning a classic bike, but once all the worn parts are replaced you will get long life out of your bike, it will be reliable if you keep up with the maintenance and it will be around for a very long time if you look after it, if you intend to keep the bike spend the money to make it right, if you can do most of the work yourself you will save a lot of money and having it fully rebuilt will put your mind to rest when out riding, just remember anything that is over 40 years old will need money spent on them in time, but doing most of the work yourself is the best way to know your bike, good luck with it.

Ashley

Essential pre-purchase cam reading -
cams-t12813-105.html

Here are my followers, with the close up pics showing the worst ones.





ashman: Ive been here before, i have a Triumph T100 that i rebuilt the engine for. i had hoped to not have to touch the norton for years

Ouch

Hi Adam, tappet clearances will be a bit easier now you know what cam you've fitted. I've got a 21 tooth sprocket in my 750 for motorway stuff, suggested by Nick Hemmings and a 19 for dodging about on a 750 and both work fine for me. Are you going to shorten the pushrods for the skimmed head or have they been done? I hope the guy that does the crank makes a job of the journal radius , if not I'm told it's only trouble but plenty have cocked up in the past as I'm sure you've heard.


Best of good fortune for the rebuild. Jg

Those cam followers are toast, as would be the cam that was grinding away at them.

grandpaul said:

Those cam followers are toast, as would be the cam that was grinding away at them.

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this was confirmed by Peter Lovell
I've ordered new ones, and all the other parts required