Norton commando 750 1972 - Valves and seals

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chiccogarz

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Sep 17, 2013
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Hi all,
I am about to rebuild my norton commando that I bought two years ago from a seller in Missuri. It is about two years that is in the garage into pieces. I disassembled it sometimes ago but I could never start the rebuilt. It is now time so I bought some replacing components and I am putting together the engine head. I was comparing the new components (left side of the pic) with the old ones (right side of the picture) and I noticed that:

- Valves shape is different
- Valves seals are different

I checked with the seller and the valve kit is the correct one (genuine norton). So, the questions to you expert is:

1. Why have they changed valves shape?
2. Why do I have that valve seals?
3. Why do I have completely different cirlce clips?
4. On the left side, of the four valves which are the inlet and exhaust valves?

Many thanks in advance

Norton commando 750 1972 - Valves and seals
 
It's time to hand it all parts included over to a competent head rebuilder machine shop . Where do you live ?
 
chiccogarz said:
1. Why have they changed valves shape?
Click to expand...
One reason could be that "flatter" (back-cut) valves flow better. Assuming everything else checks outs to be within factory specs, then you should be good to go.


chiccogarz said:
2. Why do I have that valve seals?
3. Why do I have completely different cirlce clips?
Click to expand...
Those look like what used to be called "Perfect Circle" seals, in that they're an actual scraper versus the old-school umbrella "seals". The different circlip is merely a function of the supplier. There should be a small recess around the outside of the seal for this clip, probably towards the end that slides over the valve guide. Typically, the circlip is installed on the seal, a bit of engine oil is applied to both the inside of the seal and the tip of the guide, then it's pressed home.


chiccogarz said:
4. On the left side, of the four valves which are the inlet and exhaust valves?
Click to expand...
Intakes are larger, since the only thing filling the cylinder is outside air pressure. Exhaust has the advantage of the piston force to drive out the bad. Anyway, the head's valve seats should clue you in to where the valves go.


Please keep us updated with photos as your project advances!

Nathan
 
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