Breather ball

rowdypat

rowdypat

Hero member
Location
Melbourne
Does the breather ball in a 750 shrink over time? This one measures about 19.65mm diameter. Have another used one which is within 0.1mm of this.
Has been letting a little oil escape for quite a while now. Not a lot but enough to get messy. Will put a longer hose on to get it out of the way. Oil fill level no worries. Cheers
 

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Discovered a third ball  :o amongst my spares. This one measures 20.00mm Have installed this one.
Interestingly I have two cam covers that accept a breather adaptor with about 24mm thread. Another one I have takes an adaptor with about 28mm thread.
 

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Breather balls can swell with age due to absorption of oil fumes.
Drop each from shoulder height and see how far they bounce. If dud they bounce quite high.
If ok they hardly bounce at all.
Back in the day a new 500 was smoking out of the breather tube. Swapped to a new ball and problem solved. Previous ball had swollen and jamming so couldn't do it's job.
But if yours is smoking it may also be due to excess pressure in the cases.
I would do a compression test.
 
Later breathers were enlarged to ease air movement.  Really noticable at higher revs, no great difference when just tootling around.  Race engines often benefit from a second breather.

piet
 
just make sure the breather is working correctly.....

as Piet said, adding a second breather can be beneficial on race engines, or even street engines that are run hard and revved high.

on my 79 Honda CBX 6 cylinder turbo build, first I enlarged the stock Honda crankcase breather, then I (very bloody carefully) added a second and much larger aftermarket crankcase breather which finally solved the crank venting issues used together with a Moroso air/oil separator  https://www.summitracing.com/int/parts/mor-85474/overview/ rather than venting back to the intake or dumping directly on the ground like the original crude but effective Laverda system.

"back in the day" around here, one local shop advocated a secret speed trick for Laverda engines to just remove the ball from inside the breather, was as stupid an idea as the general overall quality, or lack thereof, of that shop's general workmanship, thankfully long gone now.......

Paul LeClair
 
PCV (Positive Crank Case Ventilation) check Valve: One thing I've learned about these is never point the dump hose under the rear tire as one never knows when your engine is about to puke. Probably best to direct the hose over the chain or into the Air Breather Box, if you use one. Perhaps into  the Carburetor Manifold Plenum.
 
Thanks for responses chaps.
Piet, when would you say the larger adaptor (and hence, different cam cover) was put on the 750? With the SF3. ? It seems the larger adaptor is same as utilised earlier on the 3C  ???
 
rowdypat said:
Thanks for responses chaps.
Piet, when would you say the larger adaptor (and hence, different cam cover) was put on the 750? With the SF3. ? It seems the larger adaptor is same as utilised earlier on the 3C  ???
Click to expand...

My late ('76-ish) GTL has the larger breather port, reckon the SF3 must have had them from the start.  Yes, same thread as on the triples.  Early triples had the hose connector in alloy, later was black plastic, honestly don't remember what the twin item looks like, need to lift the tank of the GTL...  ::)  The later plastic bit had a small bar on the inside preventing the ball from blocking the breather exit when pistons pumped air from the case.

piet
 
MarnixSFC said:
SF2 had the big breather too.

Marnigx
Click to expand...
Yep, introduced on the SF2. My SF1 had the smaller one and Wolgang sells SF1 (or pre-SF2) top covers with the thread enlarged for the bigger vent. Stock SF2 has the bar, but Wolgang's aftermarket alloy vents don't.

If rings are worn, they will pump oil and blow seals out with the smaller breather! As grant said, if you are getting a lot of oil vapour it's probably a sign of worn rings.
 
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