Update on my '73 Hi-Rider acquisition.

Deckard said:

A better bolt on breather upgrade. Sure, pricey, but you'll never regret any purchase from CNW.

1972 Engine Breather Modification

Experience an increase in engine performance Eliminate persistent leaks at gaskets, seals, tach drives, head, crank case joints and more Lower the operating temperature of the engine oil The valve can operate consistently during a far higher rpm range than the Commando engine can ever reach The...

coloradonortonworks.net

The 72-73 750's actually have the breather in the most desirable location on the engine.

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I love the engineering, but not the price. A simple XS650 type reed valve is an easy install (in-line in the existing breather hose to the oil tank). It works beautifully in my experience and cost £25 + postage. I got mine here: https://www.hollandnortonworks.eu/en/exclusive-commando-parts 2/3rds down the page.

I still have a lump to cut (2) reed valves from; I used to sell them for $25 each + postage.

I believe Don Pender, aka Madass on this forum, sells a nice reed valve for the ‘72,’73 750s, (lower left rear of the crankcase) at a pretty good price, but you have to add shipping from the Philippines. Still probably cheaper than the one from CNW.

luckyed said:

I believe Don Pender, aka Madass on this forum, sells a nice reed valve for the ‘72,’73 750s, (lower left rear of the crankcase) at a pretty good price, but you have to add shipping from the Philippines. Still probably cheaper than the one from CNW.

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I didn't know Don offered this, great price of $80. It can't cost a fortune to ship something that small. I bought a whole front brake and it didn't break me to ship.


scroll down to the bottom for it.

Mart UK said:

I love the engineering, but not the price. A simple XS650 type reed valve is an easy install (in-line in the existing breather hose to the oil tank). It works beautifully in my experience and cost £25 + postage. I got mine here: https://www.hollandnortonworks.eu/en/exclusive-commando-parts 2/3rds down the page.

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That certainly will do the primary job well. It will not do the secondary job at all. The valves mounted near or at the bottom of the crankcase will clear a wet sump WAY faster than the oil pump.

Also, what you have requires machining. None is required for the 72/72 crankcases with the replacement for the standard breather and none is required for the other crankcases with the types that screw into the bottom. When rebuilding an 850, I do the big change and send the crankcases to cNw for the complete Jim Comstock breather upgrade but of course, that is expensive - lots of machining.

Deckard said:

I didn't know Don offered this, great price of $80. It can't cost a fortune to ship something that small. I bought a whole front brake and it didn't break me to ship.

Norton Commando | tritonmotorcycleparts.com

scroll down to the bottom for it.

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The Don Pender 72/73 breather is a quandary for me. I work with Don, Matt (cNw), and Jim Comstock. Don's is a copy of the one Jim designed and Matt makes and sells. It's always cheaper to copy something than develop it. Since (as far as I know), there is no patent, Don can do as he likes, it's just not nice, IMHO.

Both Don and Matt sell similar upgraded front brakes and Don's is a lot less expensive. They are similar solutions, not a copy. Don's has a no-name caliper and some other things that allow it to cost less. If money is no issue and they both have them in stock (not always true for either), I recommend cNw but am happy to recommend Don as well.

For the benefit of Quawk, the major benefit of a reed crankcase breather is that it allows the pressure created by the downward stroke of the both pistons but does not allow gasses from the oil tank to be drawn back into the crankcase on the upward stroke.
A 72/73 750 is ideal for upgrading the breather that is already located on the rear of the crankcase. Earlier 750's or 850's will need to have to send their drive side case out to Jim Comstock to have it machined to mount a breather if that's the location that's desired.
Breathers in the sump drain, rear of the timing side casting or inline in the breather hose are available.
It's just a no-brainer for a 72/73 750 to just upgrade the existing breather.

Deckard said:

Breathers in the sump drain, rear of the timing side casting or inline in the breather hose are available.

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If both types of reed valve breathers accomplish the same task, which I assume they do, why go to the trouble of installing the type that goes on the sump drain on the case, rather just putting one inline on the breather hose? I've seen some pics of installations of them on the breather hose and if placed cleverly, they make a clean installation and, it would seem to me, to be much easier and cheaper.

quawk said:

If both types of reed valve breathers accomplish the same task, which I assume they do, why go to the trouble of installing the type that goes on the sump drain on the case, rather just putting one inline on the breather hose? I've seen some pics of installations of them on the breather hose and if placed cleverly, they make a clean installation and, it would seem to me, to be much easier and cheaper.

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The sump type serve two purposes, reducing pressure pulses and clearing excess oil from wet sump events between rides. So yes, a better option if price is not a concern.

quawk said:

If both types of reed valve breathers accomplish the same task, which I assume they do, why go to the trouble of installing the type that goes on the sump drain on the case, rather just putting one inline on the breather hose? I've seen some pics of installations of them on the breather hose and if placed cleverly, they make a clean installation and, it would seem to me, to be much easier and cheaper.

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I ran the XS breather 40,000 miles. Works great.

I know others that run the automotive brake vacuum booster check valve... for decades, still working great.

Tornado said:

The sump type serve two purposes, reducing pressure pulses and clearing excess oil from wet sump events between rides. So yes, a better option if price is not a concern.

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Can you explain a little bit of what you mean by wet sump events between rides? I understand from looking at pics and diagrams and parts views, that these bikes use what looks to me would be considered a dry sump. Dry sump systems were something that's been used in race cars and other high performance machines to gain a few horse power for many years.

quawk said:

If both types of reed valve breathers accomplish the same task, which I assume they do, why go to the trouble of installing the type that goes on the sump drain on the case, rather just putting one inline on the breather hose? I've seen some pics of installations of them on the breather hose and if placed cleverly, they make a clean installation and, it would seem to me, to be much easier and cheaper.

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The inline breather does not do the whole job. See my post #25, this thread. Also, the "inline breathers" are usually PCV valves, and they are meant to be upright or nearly so - so they may not even do the primary job well. Reed valves close by spring action.

quawk said:

Can you explain a little bit of what you mean by wet sump events between rides? I understand from looking at pics and diagrams and parts views, that these bikes use what looks to me would be considered a dry sump. Dry sump systems were something that's been used in race cars and other high performance machines to gain a few horse power for many years.

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Are you familiar with Wet Sumping?
There is no check Valve on a Norton. The gravity fed oil will seep past the pump into the crankcase when not run for awhile.
The crankcase fills with oil making it harder to start. Crankcase doesn't empy till running and pump scavenges it back.
The Reed valve on the crankcase allows the oil to be pushed through on primary kicks prior to firing.

LAB put me onto this. This is what I've done. 2 minutes to check and empty any wet sumping, if I've left the bike for a month:
The small drain plug means no wear to the engine casing if you frequently empty the sump. It's simple, easy and a nice way to check oil between changes.

£25 for a reed valve (850mk3, no machining was required) and £25 for the sump plug. Two problems sorted

Mart UK said:

LAB put me onto this. This is what I've done. 2 minutes to check and empty any wet sumping, if I've left the bike for a month:

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Only, it doesn't fit '72 and '73 750s as they don't have the plug.

Ah, penny drops. How do you empty the sump for an oil change on them?

Mart UK said:

How do you empty the sump for an oil change on them?

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They have the small drain bolt '32'.

To Elaborate , the oil in the tank goes past the oil pump gearwheels , back into the engine , under gravity . if its not all 1000 % .
Its pretty normal , to have a little grey smoke , a puff & a minute or two to clear . Stops the mufflers rotting .

Its Normal to face the pump body & endplate on glass with grinding paste to around a thou. end float . No More .

But in say 10.000 miles , it mightve got out past the thou. So that Oil under gravity quitely seeps past . Overnight .
Thrown on the bore walls by the flywheel , it lubes the bores rings & pistons salubriously at start up .
Like oil leaks keeping the salt off and stopping it rusting , The Neigbours might be worried . Let them .

Only if it fouled plugs , would you have to pull your finger out , pull the timing cover , and service the pump .

OIL: CHANGE . cunning swine have a accessable - remooveable - oil return line . Tank End .

DrainTank . Inspect with flashlight . A lint free rag on a stick , to degook gunge in the bottom . If Prescent .
Said cunning sods ALSO have a strong magnetr on the Oil Tank ( and engine ? ? ) DRAIN PLUG .
To collect magnetic particals .
Like Old ' element ' oil filters in detachable permanent canisters , rather than current disposeable ones .
The R A F mechaics Checked the Filters for ' forign matter ( and bits of engine ) before setting the aces
loose on the Hun .
So thats THAT .

With the tank & cap cleaned and replenished AFTER youve replaced the drian plug , Fire it up with the return line
into a milk jug or suchlike , After a minute or less , there should be only virgin oil emergeing . Shut Down . Refit Oil Return to Tank,
and youve 100% New Oil . Uncontaminated by reminants of previous lot .

This is why CAR you whip the filtrer off HOT to drain the oilways . They can contain a good amount . And drain sump immeditely after .
A 1/2 hour lets it all drain down , from upp top & the insides . Before filling filter refitting and replenishing sump. Plug Insalled
so 2 gallons oof 6 / 110 oil dont end up at the back wall off the garage at floor level . We Double Check THE PLUG . Nip , then Firm .
Overtigtening and the tank / sump threads suffer . As you will later then . CLEAN the threads , plug , washer off . And Washer .

Have A PLACE to PUT THEM untill required . So as not to play ' Hunt the Sump / Tank drain plug '' . Then CHECK LEVEL
take it round the block , And Check Level Again after returning . THEN you can figure consumption / Milage .

Jags were 1000 miles per pint , or so . And had FELT engine oil filters . That needed WASHING at serviceing . Or clogged and

indicated low oil pressure . Where it wernt if cleaned . The NORTON is just a GAUZE SCREEN to collect rocks and small children who fall in .
Therefore were a bit fussy regarding grit and dirt road dust about the cap & fittings . A bit of oil film collects it , but it hoses off leaving the machineary preserved . KERO in the Steam Cleaner keeps it rust free . Hot Water Only . Watch It . The Olde Oxide will get going in moments .

A V slight damp patch at the head gaskets notta worry . bubbling when running would be .
Heating copper gasket red hot and dropping into water ,softens / anneals it . They REUSED them too . Unless damadsged .
Of course copper graphite paste , KoperKoat , was used in Nitro Burning Triumphs to keep the combustion internal , on the Salt.

Wash , clean , reaneal , and reuse Copper Gasket . Often even works on fancy laminated modern gaskets . As they Dont Stick and tear , removing them .
Coppr Coat is Pressure Sealing Anti Sieze Compound . A BSAestte used Steam Pipe bituminised pressure sealing gasket paper to make all but head gasket , the only mark on the dust coated bike after a back road cruise was a petrol drip from having used the tickler on the Concentrics . The left one , on the side stand . And THATS ANOTHER THING .
Get Used to Balancing it Whist Leaping skyward , kick start ENGAGED beforehand after having pushed thru to Near T D C

From Cold , Free Clutch , prime carbs , push through four compressions to prime . THEN ' Contact - Switches ON ' and it'll one kick light up .
Quite halarios hearing hilarity at the pushing it through " Arrghhj It wont start . twitter giggle " deafed at the first compression with intent .

So waner round it to see the wings arnt falling off , or the preopellor . Gun Switches ' safe ' . Before ' all clear ' ' Chocks Away ' .
At which stage your full attention is available FORWARD for obsticlal obstructions and intruders ! . Like the Flying Scotsman .
Brakes Checked . Throttle ' on ' . Feet Aboard Imediately . Swiftly and with style . ! Instruction for the operatrion of correctly :

Take No prisoners .

Matt Spencer said:

DrainTank . Inspect with flashlight . A lint free rag on a stick , to degook gunge in the bottom . If Prescent .

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A good/bad thing about a Commando oil tank is that the feed line is not near the bottom of the tank. This means that heavier particles can sink to the bottom and not be fed to the engine. But it also means that a lot of oil is not in circulation.