70 crankcase breather (2013)

I am putting a 1970 engine, mostly standard, together. Any ideas for better crankcase breathing? It has only the camshaft breather. There is one hole into the timing chest, behind the cam bushing and has the blanked off magneto mount, not tin. Thanks

Send the drive side case half down to me and I will machine it for a reed breather. Jim

Are you saying the right side case is cast over on the magneto mount area? If so you may have mis-matched cases (they weren't cast over till 73) unless someone has taken the trouble to align the cam and crank bosses so they are a set.

RennieK said:

Are you saying the right side case is cast over on the magneto mount area? If so you may have mis-matched cases (they weren't cast over till 73) unless someone has taken the trouble to align the cam and crank bosses so they are a set.

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Not sure you're right on this?

Some later 750 cases had a blanking plate for the electric starter which never happened, but I've got some '70-71 cases with the timed breather and no blanking plate.

an alternative solution would be to remove the timed breather (requires cam-bush removal) and connect the breather to an external PCV.

Jim's solution would be the most elegant though!

I could be wrong but by memory I never saw rt side cases with the cast over mount till 73.

At any rate cases should be stamped as pairs with the 3 didget code.

RennieK said:

Are you saying the right side case is cast over on the magneto mount area? If so you may have mis-matched cases (they weren't cast over till 73)

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Not necessarily, as the starter motor blanking plate was apparently introduced at engine number 136618 (according to the INOA Tech. Digest) which was around mid-1970. Prior to that, the area was cast over on the early 20M3S models as it was again from around the latter half of 1972.

http://atlanticgreen.com/engcases.htm

No one can say anything firm about Norton production variations. BOTH my unmolested Combats, early one March '72 & the later one Spet. '72 BOTH have completely cast in face where the ole magneto went yet all numbers match on the stem and case stamping.

My crankcases appear to be matched. It has large x marks on both cases near the bottom and has 3 digit numbers hand stamped in the inside of both cases, below the cylinder spigot, #154

Thanks for setting me straight guys and sorry for the confussion. I wasn't aware of that style of case andI always figured timed breather = points behind engine. Guess that somewhat explains the breather drive on the points off cam camshafts too.

RennieK said:

Are you saying the right side case is cast over on the magneto mount area? If so you may have mis-matched cases (they weren't cast over till 73) unless someone has taken the trouble to align the cam and crank bosses so they are a set.

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I have a 134818 with right case with side cast over the magneto mount area and it matchs with left case!

Here is some historical reading. I am sure there are others.

inline-breather-valves-revisited-t7637.html?hilit=breather
breather-valve-problem-t7562.html?hilit=breather
xs650-breather-exposed-t7345.html?hilit=breather
one-way-breather-valve-differences-t5929.html?hilit=breather
xs650-mount-near-tank-breather-t5866.html?hilit=breather
crank-case-breather-t3680.html?hilit=breather

I have become convinced that Jim's breather off the back of the case is the premium solution. Ludwig adapted a breather to fit inside the timing chest but it "sucked" out of the crank case. That was an elegant solution. Jim also has a breather that screws into the large sump opening. As for putting an XS valve on your bike, I am not confident that having it breath from the end of the cam will be a big benefit. You might find information on that in those posts above, but a lot of it is subjective. I give Jim's breather the high score because he actually measures, tests, and records observations. I don't know if Grandpaul is still selling a breather or not. There was controversy (imagine that!) over whether or not pulling from the timing chest was a valid solution. However, it is possible his idea could be transformed into a Ludwig style breather by mounting it on the outside of the mag area but plumbing it into the crankcase via the timing chest. How confident are you about drilling and cutting on your cases? (yikes!)

You comment that you have one hole between the timing chest and crank case now. That is usually where the modification ends up after plugging holes between the two. Got any photos? Is that normal on a 70 vintage case?

Sometimes you get reactions from members that these topics have been beaten to death. And yeah, lots of 'em have but it is still good to get 'em out and dust them off once in a while. You never know what you (or even better, I) might learn!

Russ

I cut and pasted the old threads from another thread and didn't realize the links did not transfer. Here is the thread from which those links where copied:

pcv-valve-t8790.html?hilit=breather

comnoz said:

Send the drive side case half down to me and I will machine it for a reed breather. Jim

Click to expand...

Hi Jim,

What is the differences between a reed breather and your last breather that i bought from you and i have mounted on my 1422..; maybe only that the reed goes back and your that i have goes under?

Now, i have a 134818 in the picture below with right case with cast timing side:



I would open a hole on the cast blanking side and fit the complete 1972 breather that i have.

It is a good idea?

It could work well, what i must to do, open or plug some of the holes on the timing case in the picture?

Thanks.

Piero

pierodn said:

comnoz said:

Send the drive side case half down to me and I will machine it for a reed breather. Jim

Click to expand...

Hi Jim,

What is the differences between a reed breather and your last breather that i bought from you and i have mounted on my 1422..; maybe only that the reed goes back and your that i have goes under?

Now, i have a 134818 in the picture below with right case with cast timing side:

I would open a hole on the cast blanking side and fit the complete 1972 breather that i have.

It is a good idea?

It could work well, what i must to do, open or plug some of the holes on the timing case in the picture?


Thanks.

Piero

Click to expand...

Both breathers I have are reed breathers and use the same reed valve assembly.

I have one kit that requires machining the lower left part of the case to install it. Usually done with a rebuild. It is out of sight and requires no service.

The second breather is the sump plug breather. It is built with the idea of being easily added without tearing the engine down. Jim

Here is the machining needed.

comnoz said:

Both breathers I have are reed breathers and use the same reed valve assembly.

I have one kit that requires machining the lower left part of the case to install it. Usually done with a rebuild. It is out of sight and requires no service.

The second breather is the sump plug breather. It is built with the idea of being easily added without tearing the engine down. Jim

Here is the machining needed.

Click to expand...

Have just fitted this, as purchased from CNW.Do I vent to atmosphere.I have 70 roadster,with the oil breather vent on left hand front of case.

coomo said:

Have just fitted this, as purchased from CNW.Do I vent to atmosphere.I have 70 roadster,with the oil breather vent on left hand front of case.

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Definitely not. The breather should be vented to the oil tank as the breather picks up any oil in the sump. It evacuates the sump fairly smartly. Big mess if you vent to atmosphere.

Ok thanks.So I vent to this spigot on oil tank.Obviously i now delete breather on front LH of case, as shown