To Replace or not Replace, That is the Question.

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Dec 5, 2003
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Fellow Nortonphiles

Got my crank disassembled the other day to clean and prep for balancing and started to put it back together but stopped :shock: Should the bolts and nuts that hold the 3 pieces together be reused or replaced? BTW I did have enough sense to mark the pieces so they will go back as original.

"Should" they be replaced? The safe answer is yes. However, if it is a street motor that will not see a lot of use above 6000 rpm and inspection shows no burred or pulled threads I will generally re-use them. If it's likely that the motor is going to be buzzed hard or it's a highly modified street motor, then they get replaced.
I agree with Ron's raison d'être regarding stud and nut replacement. If anything, you may want to consider replacing the nuts, but it's not a "deal breaker" if you don't.

Now regarding your unmarked components, you need to mention this to the person that will be doing your balancing. He or she may have to un-bolt the assembly and reverse the order upon reassembly in order to optimize the weight distribution.


crankshaft bolts & nuts


I remember a warning about new nuts and bolts for the crankshaft. Maybe in the NOC Commando Service Notes, the new parts are sharp where they contact the crankshaft and shave metal when torquing. This then gets into the oil passageways. So, when using new parts smooth them with some abbresive.
To Replace or not to replace

Good advise, however, I have always used the old ones if they appeared too be in good shape, torqued w/just a drop of Locktite, the only failure I have had was a set of new ones, and yes, I spin them up.
I took one apart in '82 and I can't find my mark on the flywheel as I cleaned a bit of rust off with some 4ought steel wool. Is there any difference at all that would show which side was which?
Dynodave has an excellent point: New hardware is often poor quality.

For instance, the '75 Commando engine crankshaft uses studs with a slight interference fit. However, most new replacement studs can be dangled around inside their holes in the crank. Sadly, there is no quality control for replacement Norton parts, especially fasteners.

So the "crux of the biscuit" is to reuse original fasteners if at all possible.


Thanks for the wisdom. I too am suspicious of some of the new manufacture parts so will reuse the originals.

I have just completed this little job also this afternoon. As the conrod nuts were not mentioned, I guess most would realise that they should be replaced. No harm mentioning it I thought.

I have also installed new circlips for the piston gudgeons as I have heard of these "coming out" inside the engine.

The bottom end is now together & bolted into the frame, woohoo. It should not be long before it is fired up. Now, should I use points or go "electronic" ?

This 850 has a brembo 4 pot caliper mounted on the front. Does anyone think this should be removed and replaced with one of those good TLS drum brakes ?

I have replaced the "ratty old amals" with a single 43mm mikuni, can anyone tell me the jet size that it may need. The head is a stock RH4 but the cam is a 3S.

My first two questions are only a dig for those that don't pick up on it.
But if anyone knows the "right" size main jet I should try, advice would be appreciated. TIA.
A Brembo on your Norton? Italian parts on your Brit bike? I'm sorry Reg, that won't do at all. You'd better remove it immediately and send it to me. I have a Brembo-equipped Ducati in the garage so your caliper will feel right at home. I'll send you the TLS parts in exchange. Well, you'll have to send me some cash too. I hear the TLS stuff is in demand now. You'll be stylin' :)

BTW did you mean "34mm" not "43mm"? The INOA Tech Digest has jetting recommendations. That might be a good place to start.

Back to our regularly-scheduled thread contents...

Thanks Debby, I did mean 34 mmm.

Now what size Jet please ??

One piece of literature I do not possess on nortons is the INOA Digest. If you can mail me one, I will send you the cost involved.

As this forum is such a wealth of info, who needs it though ?

But, yes, I would like one if it is possible.
Here's what the book sez for an 850 with single 34mm:

main 230
needle jet 159 P2
needle 6DH3, middle notch
idle jet 40
slide # 2.5
idle air jet 2.0

Thanks Debby, that's what I need.

Now I have to repair the crack in the bottom of one my oil tanks, connect the wiring & install another of those crappy electronic ignitions & she will be a goer.

Italian front brake, taiwanese inner tubes, german & japanese bearings............. :!:
Why did those British Bike manufacturers have to all go broke.......
to replace or not to replace

Do you still use the stock Norton rotor with the Brembo parts, or have you switched to CNW type Brembo rotor? Do you use a fork brace ?
I am thinking of adding a bevel Duc. forks (Darmah) to my Combat, It already has Del'Ortos on it using Amal Mk2 manifolds. What are your thoughts.
My 750 has a Brembo Master Cylinder with the stock norton caliper & rotor. The improvement over the stock Norton Master cylinder is very noticeable to me. I would recommend the upgrade to anyone.

My 850 is not on the road yet, but will have a Brembo Master Cylinder & 4 pot caliper with a stock norton rotor(drilled) for now. I intend buying a floating type when I can afford to. I have also thought of installing one of the Norman Hyde Fork Braces when I can.

So, I may be riding the 850 next weekend if I "steal" the master cylinder & ignition/wiring from my 750. You can bet I will do that, as I want to "take the 850 for a spin".

I can't tell you any more until I do some miles on it, but I surely will answer any questions I can.

I am in the ptrocess of installing the pistons/barrells as we speak.

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