1977 commando rebuild

Classic Norton Commando Motorcycles.

Re: 1977 commando rebuild

Postby Jed » Wed May 02, 2012 2:48 am

Thanks Lab for the info on the timing chain

You too hobot but If something aint broke why fix it
The bike had 32000 miles on the clock, the bore/pistons were good and if I were you I would be checking the tension of my timing chain
Metric or imperial if the info is wrong it aint worth poop!

While I have pulled motors apart including the crankcase this is my first Norton so I don't consider myself a restorer but an enthusiast

Cheers and stay right side up

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Re: 1977 commando rebuild

Postby Josh Cox » Wed May 02, 2012 5:02 am

Less than a 1000 miles.

The last bike i restored was a BSA, it has a different type of sludge trap, it was entirely blocked, infact i had to blow the crap out with an oxy accetaline.
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Re: 1977 commando rebuild

Postby DogT » Wed May 02, 2012 7:10 am

Here's what mine look like at 13K miles and no filter.

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Re: 1977 commando rebuild

Postby Jed » Thu May 03, 2012 2:40 am

Thanks for the heads up on that crap residue hide hole
Looks like another topic for the knowledgable ones at our next classic bike meeting
Problem is after seeing that I will be wondering if I should be pulling my motor down after another 13K miles
By the way Dog T is that wear in the centre hole where the sludge came from or is it just the photo?
It would be great if you could post more info on your builds as they progress

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Re: 1977 commando rebuild

Postby DogT » Thu May 03, 2012 6:42 am

I'm not sure where you thing the wear is, but, no wear. Just the metallic crap that's easy to clean out. If you want to go through my 31 page rebuild go here phoenix-rises-again-t5905.html Swooshdave had a long thread on his too. There are several others around, I should make a list of them.

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Re: 1977 commando rebuild

Postby Jed » Fri May 04, 2012 3:06 am

The photo looked like some irregularity on the inside of the crankshaft which is where i thought the metallic crap came from but it is just some of that that stuff on it
Thanks for the link Dave and the posts. You sure have done a great job and looking at your posts I realise I need to take my time to make sure I do it properly. My worry is that if mine looks as good as yours I may be too scared to take it on the road!

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Re: 1977 commando rebuild

Postby swooshdave » Fri May 04, 2012 8:51 am

DogT wrote:I'm not sure where you thing the wear is, but, no wear. Just the metallic crap that's easy to clean out. If you want to go through my 31 page rebuild go here phoenix-rises-again-t5905.html Swooshdave had a long thread on his too. There are several others around, I should make a list of them.

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Re: 1977 commando rebuild

Postby shrugger » Sat May 05, 2012 7:20 pm

WOW! some insignificant sludge trap residue. :P
Here's a real mans sludge trap. 60% full at aproxamately 25k miles.
From my (lesser breed) Triumph. lol
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Re: 1977 commando rebuild

Postby Jed » Thu May 10, 2012 12:43 am

Pardon my ignorance but-
Would anyone know if flushing the bottom end out with petrol or some other solvent is advisable or would it adversely affect other components?
I thought I could plug the hole to the timing chamber and give it a petrol bath to get rid of any crap that might be in there but it seems a bit radical
Norton guys I spoke to did not think much of the idea maybe because things may dislodge and end up in other places
I was recommended to do a few quick oil changes once it was running and not use a detergent based oil

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Re: 1977 commando rebuild

Postby L.A.B. » Thu May 10, 2012 2:38 am

I doubt attempting to flush the crankcase with petrol is likely to achieve much, and won't be of any value at all as far as clearing out the crank sludge trap is concerned, and in any case, you don't really want to loosen anything inside it. The level of sludge build up inside Norton cranks shown in the previous photos is insignificant and of no real concern (when you compare them to the Triumph sludge trap).

The sludge trap is a centrifugal filter-so some build up of debris after a significant amount of mileage is to be expected. The advice you were given about using a non-detergent oil is basically unfounded in my opinion-as it's unlikely that a detergent oil would cause any problems and is probably what has been used in the engine up to now-unless you know otherwise?

If the thought of the sludge trap being blocked seriously bothers you, then there's no other way to do it, but do it properly, by splitting the cases and crankshaft and cleaning it out! :)
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Re: 1977 commando rebuild

Postby shrugger » Thu May 10, 2012 4:48 am

Whats in the Trap is is made up of carbon and microscopic bits of metal. Quite solid and solvent proof. If you could begin to
wear it loose, the only path for it to take is past the rod journels. They would quickly wear from it neccessitating a rebuild anyway. :cry:
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Re: 1977 commando rebuild

Postby Jed » Fri May 11, 2012 2:16 am

Thank you once again for the advice
It may seem slack not splitting the case but everything is good and tight down there. Besides it's a good reason for an overhaul down the track when a rebore is needed
The head and barrels aren't back from the shop yet and will post photos once they come back and the powder coating is done

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Re: 1977 commando rebuild

Postby Jed » Sat Jun 23, 2012 11:23 pm

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So far so good
The silver powder coat with a clear finish came up great. The photos don't do it justice
The bloke quoted $360 for the job (silver was $60 extra) but charged me $100 more when I picked it up. Bit sudden but the job he did was worth it
He had a whinge about not cleaning the bits properly, in hindsight a steam clean before taking it would be better if you have the time
I did degrease and pressure clean it but admit was probably not as thorough as should be
Other club members have had their frames done but I don't think he realised the job or parts involved on a commando
The head was OK just dismantle, service & grind - the barrel honed & sandblasted they look great

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Last edited by Jed on Sun Sep 15, 2013 2:41 am, edited 1 time in total.

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Re: 1977 commando rebuild

Postby Jed » Sun Sep 15, 2013 2:38 am

After putting the build on the back burner for a while I finally got up a head of steam and after some thought decided to take the advice of the Norton elders and split the crankcase
Hobot threw out the challenge to be a bone-a-fide restorer by splitting the crank so thats what I did
There was about half a teaspoon of material in the sludge trap.
Since using a different type of oil to what the PO used may free the sludge causing a blockage in a journal somewhere was not worth chancing
Everything else was good.
Superblend bearings are in the big end and I am not sure if this was a later thing or introduced on the Mk3
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My box was cracked badly so the older box I found needs to be modified to suit
Differences between Mk 3 box on the left and the older box on the right are -
Spigot needs to be milled on the older box to take the cross over shaft
Neutral light switch needs to be tapped in and hole chamfered on the neutral locator to take the O ring
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Bottom end assembled
I am thinking at this point I will call the bike Murphy as it seems that is the law it abides by
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Putting the pistons back in only having needed to replace the rings at this point because thankfully the pistons and Barrels were good
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Barrels were put on the block without a gasket, just a good quality sealant
You should be able to see fishing line fed up through the engine to the top of the barrel which had a piece of cotton rag looped around the end
This was pulled through to clear any remnant of sealant etc which might potentially cause a blockage
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The Darlek is almost complete!
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Into the frame goes the powerplant
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The SU carburettor is a curiosity and it will be interesting to see how this goes as there is not a huge amount of intel on the use of this on a bike
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A new primary chain was no different just a couple of mm shorter. It seems crazy not to be able to adjust these but I guess they don't wear much
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The rims will be good for a while yet and though there are a couple of blisters on them stainless spokes really cleaned up the look of the rims
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Electrics are in and everything works!
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Both front & rear matser cylinders needed work. The front had the half inch SS resleeve and the back seems to be taking OK with just the seal kit but it seems to be still a bit iffy. They are not meant to be that flash at the best of times so it's hard to know what is good
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Last edited by Jed on Mon Sep 16, 2013 2:45 am, edited 1 time in total.

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Re: 1977 commando rebuild

Postby cjandme » Sun Sep 15, 2013 8:17 am

Great thread, thanks for posting it Jed :D
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