Engine Breather - 750

I'm building a 750 with a few subtle upgrades, and I want to improve the engine breathing arrangements.
It's a 1970 motor with a timed camshaft breather and drillings for a breather boss on the timing case.

I'm planning to use a MIke's XS PCV reed-valve, and the possible solutions I've come up with are:
1 - remove the rotary disc and the cup behind the crank pinion and tee the two outlets together before feeding them into the PCV
2 - blank off the timing case breather, remove the timed breather and feed a single pipe to the PCV
3 - blank off the timed breather, remove the cup behind the crank pinion and use the timing case breather with PCV
4 - stick with the original timed breather and don't bother.

Just fishing for other peoples' experiences I guess!
My 850 breathes from the timing case to a PCV and it's been fine, but it's only used on the road, and I'm planning to use this motor a bit more 'liberally' :wink:

Have you considered the Colorado Norton Works (developed by Jim Comstock) breather solution. Sounds like this is the time to get it right.

I'm using the original timed breather, for whatever that's worth. I'd rather have a good breather, like the Comstock one, I tried it, but my engine sits so low in the frame the brace below the sump is too close to use it. I bought one but had to return it. Wish it would have fit. Jim says all the 69/70 frames he tried it works fine.

Dave
69S

Jim has measured his results. The rest of us are just guessing.

Russ

Redundancy is not a bad thing win this reguard. I would think you could leave the current timed breather in place. Is you mag area casted over or do you have a plate in place? I have a plate drilled to take a 72 breather. You could then add the xs650 unit inline.

I've got two breathers on my '72 Combat--the conventional one plumbed to the oil tank and an 850-style timing-case breather exhausting to atmosphere through a mini-pod filter--it is truly amazing how much air moves through both at idle


Tim Kraakevik
kraakevik@voyager.net
'72 Combat, '74 RH10 850

kraakevik said:

I've got two breathers on my '72 Combat--the conventional one plumbed to the oil tank and an 850-style timing-case breather exhausting to atmosphere through a mini-pod filter--it is truly amazing how much air moves through both at idle


Tim Kraakevik
kraakevik@voyager.net
'72 Combat, '74 RH10 850

Click to expand...

At idle the engine is attempting to sweep 828cc volume each revolution. I always wondered about this and am speculating that maybe you are probably feeling the exhausting more than intake. It would be interesting to get a quantitative measure on these sorts of things.

I seem to recall a member on this list may have included a small vacuum pump on his Norton road racer.