Forum

[Barry N]

My 612 breathes out approximately 1ml of oil per mile, through the elbow below the barrel, and collects (via a duckbill) in a pot I have rigged up in the toolbox. That’s no problem at all, and from what I understand, not unusual for these engines. So after, say a 100 mile run, I have 100ml of freshly regurgitated oil to dispose of. I am tempted to just pour it back into the engine, just like our host’s breather kit does, but can’t bring myself to do this for fear of it being more contaminated (from piston blow-by maybe?) than the oil that ordinarily gets scavenged from the crankcase. Logic tells me that this oil will be no less contaminated than the rest of the oil and should just be put back where it came from – but that little voice in the head keeps telling me to replace it with new stuff, which is what I normally do. (The lot gets changed every 1500 miles anyway). Does anybody have thoughts on this? Thanks!

[Colin F]

You could fit the breather system that comes with the 2005 Bullets,as you say the oil that collects is exactly the same as would normally be scavenged.Then you would find oil usage over the 1500 miles would be negligible as i found on my 612.85k km and never needed to add oil between changes,the Acrillite rings seal much better than the stock ones.

[PeteF]

If it look OK I would pour it back in. If there is any evidence of "mayonnaise" (water emulsion) then probably not.

[neddy]

No, do not put it back in, save it fir "home" use i.e. garden tools, locks, pushbikes etc etc, if you cant afford 3in1

[Chris [Stockport]]

Barry, I'd agree that it'll be contaminated no differently from the rest of the oil in the system; ie a bit contaminated. So, why not put a bit of new oil in instead, that's not contaminated?
Chris

[ric]

When you next change the oil you'll have refilled the engine with either 1.5 litres of old or new oil.
If using fresh oil it won't take too many miles before you've outweighed the cost of new rings, possibly new gaskets, a modern one way non return valve along with some new rubber hose.
This would in all likelihood reduce the oil top ups required between your service intervals to zero.

[Barry N]

Thanks to all for the replies. Up till now, I have usually topped up with fresh, but as the discarded stuff looks in every way as good as what’s on the dipstick, I really don’t think it’s any different to the oil that gets scavenged, and it’s therefore ok to put back in.

ColinF – yes, the breather kit would certainly save the chore of emptying the catchpot and therefore maintain the oil level (it burns hardly any oil). Did you say 85,000km on your 612? That’s impressive! Would you care to tell us more about the bike? How reliable have you found it, what parts (if any) you have replaced, etc? I’ve had mine four years now and I love it!

[ChrisD]

Barry N.

When I got my 1996 500cc Classic almost new, I found it breathed out a lot of oil mist through the breather onto the chain at anything over 3500 rpm (especially when it got hot) at the rate of some 1-2ml/km. So I fitted our hosts breather mod sending all that oil back to the oil tank before the duckbill to the chain. But then, at any revs above 4000, it allowed the engine to breathe oil fumes out of every possible pore and it always dripped onto the garage floor – but that didn’t matter since I hadn’t balanced the engine and so hardly ever used higher revs.

Then I upgraded to 535cc and the leakage got worse.

Now, during my latest rebuild/rebalance, I read an email by Ace Café suggesting the breather mod was helping to pressurise the crankcase not sustain a partial vacuum and may be the cause of the constant oil film on every joint. So I removed it and replaced the duckbill the way it should have been. I then noticed the breather outlet pipe (moulded into top of crankcase on LHS) was barely 6mm ID and had a 90deg bend further occluding the gas flow. So I drilled it out to 8mm and opened the bend, leaving enough metal to secure the pipe. Now it breathes not a jot through any engine joint (crankcase, rocker cover, timing chest etc) and minimal onto the chain.

Is your problem here simply that the breather was designed for a 350 and even at 500cc there was too much vapour to eliminate, let alone a long stroke 612cc?

Cheers, ChrisD

[Barry N]

That’s interesting Chris. I have no problem at all with the engine breathing, just that I was wondering if the regurgitated oil was in any way inferior to the rest of the oil in the crankcase – and therefore ok to recycle (I am sure it is). I think my 1ml per mile (breathed into my catchpot) is quite good for the 612 and the motor doesn’t burn oil to any extent. Last week I completed a 400 mile trip touring North Wales and there was not a trace of an oil leak anywhere, so I’m very happy keeping thing as they are. It’s no problem to empty the catchpot occasionally and since I measure what comes out, it’s a useful health check! Cheers, Barry.

[Ginetta lad]

After my experience I'd be checking the oil pump worm and spindle for Wear? In good order they shouldn't blow oil out the duck bill but it will if too much oil in in the sump not being scavenged back.