Modified Breather on 1971 750 motor, comments ?

After the rebuild of my Norton 750, I had several irritating oil leaks. I had even done the "850 type" breather mod and had drilled plenty of holes in the timing side crankcase. (just like in the Mick Hemmings Norton motor rebuild video.) Frustrated ... I then followed the Norton "Tech Digest" advice of the "motormite brake valve" in the line, and the oil leaks were gone ! Then I read somewhere that the valve is somewhat "flimsy" ( it is, IMO ) ... so I installed a one-way breather I bought from MikesXS. It works great too ! Though my Norton is not perfectly oil tight, it is darn close.

Question: Where should the valve be installed ??? Top by oil tank, bottom by motor ... or as in the pics, I currently have it in the middle. Any comments are appreciated, cheers !

Everything I have read says to put the valve as close to the crank vent as possible, but I am not the expert. However, I rebuilt my 69 with all the original oil lines and the timed breather that you have blocked off, and so far no leaks, but then I have not had it on the road yet. Some claim they don't have leaks and some say it leaks out of the oil tank breather into the ham can air filter. Mine used to leak out of there all the time, and the crank, and the primary, and the gearbox. So far I have no leaks, and I did use Permatex Hylomar on nearly all the gaskets. I really think it helps. When I broke the crank cases apart there was nothing on the flanges.

Where are your leaks?

Dave
69S

My motormite valve sits comfortably just before entering the oil tank. Being a cheap humanoid it works great for years and is made of real genuine plastic. At that price I got a couple extra ones should it eventually kick the bucket , still waiting. Never seen the timed breather camshaft exit sealed up like that. On my 70 it was kinda fun to look down and see the oil blurping about through the clear line I was running at the time. Showed me visually oil was flowing. Keep your oil level on the oil tank dipstick to a tad over " L " and you should do fine.

DogT, initially ...it seemed like my leaks were; er, everywhere. I then installed the "plastic motomite brake valve" right by where the hose goes into the oil tank. Presto, leaks were gone ! Then I read that the motormite valve could easily fail. Well, I then got paranoid and installed the valve from MikeXS, which is specifically designed as a breather valve. Still seems to work great. However; though mostly hidden, I don't like the way it looks where I have it.

Torontonian, I blocked off the old breather at the camshaft ... because that's what Mick Hemming did in his Norton rebuild video. I consider him a Norton expert, and really respect his advice, so I did it too. Thanks for your comments, cheers !

Put it as far away form the oil mist and engine heat as practical. I put mine at tank level zip tied to frame where it acts as an elbow to aim breather into tank tube.

I like where you put the one way valve, nicely close to the timing cover but right where it needs to angle up to the oil tank.

You also have it located a little higher than the timing cover so any oil blown up to the valve can drain back down.

Have to agree it looks like you have a good grip on it to me. With the side cover on it would just look like it was always on there. It may not be a perfect sizing for maximum efficiency but for a cheap set up it's working and you would have to spend big bucks to make it better.

This is what I did with the unit Grandpaul sent me. Since there is no risk of oil getting in there (other than mist) get it as close to the case as possible for max effect.

Wow, luv that install of THAT breather valve pvisseriii !!! Where can I get that done, you, GrandPaul, or; contact info please.

nortriubuell said:

Wow, luv that install of THAT breather valve pvisseriii !!! Where can I get that done, you, GrandPaul, or; contact info please.

Click to expand...

You may be able to get a valve from grandpaul if he has any left. The flat blanking plates are available from Old Britts. Mine is a latter 72 case with the back casted over.
I am sure you can do this. Simply mark your holes, cut an oraface , cut yourself a simple gasket and bolt it on.
http://www.oldbritts.com/11_061542.html

Check valve does not need to be up close to work perfect. After few engine turns the big breather hose just adds volume to lower the pressure swings. But its a non issue compared to nice installs on engine mounted valves. I put Combat baffle on old points area and connected to PCV near tank by big clear tube. Clear tube never even got misted enough to show on a tissue wiped through it and Ms Peel loved red line and above flings and even tach pegging over rev, no breather issue at all.

Wow, I appreciate all the posts ! I'm gonna change the location of my valve to where Hobot recommends. (thanks Hobot!) As far as the Old Britts mod, I have no 1972 or 1973 750 cases anymore. Mine are all 750s with the camshaft type breather, or 850 cases. Any 200000 series 750 cases I get I sell them. Just don't like not having the big sump filter with the fine mesh screen, as it's at least SOME protection. Had a Combat years ago and I was going way to fast, for way too long. It siezed, and bits of metal ruined the oil pump ... as well as other things. At least it prompted my first of several Norton engine rebuilds !

Norti- you alert me to provide some screen on sump inlet as have seen what happens with a Combat cam thrust washer tab or two going through it or how much swarf can get pulled into the internal case channel to the pump, ugh. Must heat cases to same operating temps to get pieces out of stay trapped even with wire run through. Oil mist baffle should be near the engine misting but simple PCV valves better far away. Super duper check flapper valves need the solid mount to install is all. Fancy metal case Krank valves cost like $100.
Blood brothers in engine mess set backs.

Here's a photo of well used Peel Krank PCV, little silver canister in hose above tank.
The bright red is extra foam layer over an K/N air filter d/t THE Gravel dust.

Ah yes, the joys of owning a Combat ! After that motor siezed, and metal bits got into the oil pump, it pretty much trashed the motor. I then rebuilt it as a project for an engine rebuilding class. I vowed to never have metal bits (and other large swarf) get to the oil pump again ... but what to do ??? I drilled the machined bottom access hole from the front larger, then intstalled my own fine mesh screen, rolled in a tube thru it. At least now there was SOME protection for the NEW oil pump I had just installed ! I then tapped the case to access the larger ( and easily removable) grub screw in place of the old small one. Getting the "rolled tube of fine mesh" out to clean it was a pain every other oil change, but at least there was now SOME kind of protection there ! I couldn't really clean inside the larger drilled hole that well either, but at least it was better then what ol' Combat engine #201974 had before that mod ... NUTHIN !!! Cheers ...