Forum

[TONUPBOY]

Thanks, Pete. I wasn't under the impression the timing chest stub was for a breather, but is there any reason it couldn't be used as such? There's already holes between the oil tank and timing chest that allow oil to flow between the two compartments-- isn't pressure then equalized between the two? As long as both breathers have a one-way valve, is there any reason this kind of set-up shouldn't work?

[PeteF]

I found the timing chest "breather" tended to spit oil out more than you would want to use as a breather. I think that's because the oil in there will be churned up by the timing gears.

[TONUPBOY]

I concur. I had attached a blocked-off section of clear hose, just so I could see what was happening with the timing chest oil, and it looked like waves lapping at the shore. I picked up some bypass caps at the automotive store today (for the timing chest stub), along with a Ford PCV elbow, which I'm going to attach to the oil tank stub. At the outlet end of that elbow I've got a ball-and-spring type check valve, and from there a hose that I'll direct towards the chain and sprocket area. The only problem with this is that I'll need three hose clamps to fit the entire assembly, and it doesn't do much for the clean look I was going for.

P.S. My dipstick is the screw in type, and it doesn't have any sort of vent. Would you advise me to purchase a vented one to further alleviate high pressures in the system?

[Wheaters]

My bike also has an un-vented, screw in cap. I'm considering drilling and tapping a breather pipe stub into the top rear of the timing case because my engine doesn't have a distributor (350 Bullet Electra) and the three gears that would normally drive the distributor aren't fitted, only the two cam drive gears.
Can anyone see an issue doing so? When I bought the bike last year there was a noticeable amount of oil/water "mayonnaise" on the dipstick and in the timing case when I removed that later to carry out some engine maintenance.

From previous experience, if a simple plain pipe is fitted as a breather to atmosphere, it's always likely to blow out some oil because there is no room to separate the oil mixed up with the excess gases. Removing the "catch can" (oil separator) isn't a good idea, in my view, so I'll be keeping that.

[PeteF]

Tonupboy, any pipe from the oil tank stub is best routed up behind the battery before leading to the chain or wherever. This really helps stop any oil escaping. A simple duckbill on the end is sufficient as a NRT.

Weaters, that could work without the timing gears thrashing the oil about but if you have an oil tank stub I can't see the point. I get very minimum oil out of my breather which comes from the oil tank stub, up behind the battery and down to the chain (with a duckbill)
These engines are prone to "mayonnaise" as they run relatively cool but the biggest cause is doing short runs.

[PeteF]

NRV, not NRT

[Wheaters]

PeteF, My reason for fitting an additional breather outlet at the top of the timing case is because it would sit higher than the existing one in the oil reservoir and it's there where most of the mayo was collecting. Water vapour is less dense than air so I suppose that's why it tends to find its way up to the highest point in the system. Having sad that, it's not so much of an issue now I own the bike because when I go out, it gets ridden hard (including some motorway use)and 100 miles or so seems to be my usual weekend jaunt distance out in the Peak district (I've doubled the indicated mileage on the bike in the 14 months or so I've owned it).

[PeteF]

Understood Wheaters but I can't see it making a deal of difference being a bit higher.

[stinkwheel]

I've mentioned mayonnaise before. My 350 bullet had tremendous problems with mayonnaise. To the extent it would obstruct the duckbill breather I had fitted on the oil tank stub on a daily basis, I'd have to blow it through into a paper towel on each fuel stop.



That was most certainly nothing to do with short trips because it did it all the way through my Round Britain Rally trip in 2010 which I did end to end while camping off the back of the bike, averaging 150 miles a day for 3 full months and incorporating 3 oil and filter changes over that summer.



I fitted a hitchcocks scavenge pressure relief valve some time later, from that day the mayonnaise problem went away and has never happened again.



I'm not sure I can even start to come up with a mechanism for why that should be the case. Perhaps the oil being forced through the rocker blocks at an excessively high pressure makes any moisture more prone to forming an emulsion? Or perhaps the pressure relief valve constantly bleeds a portion of the scavenge back into the timing chest thereby raising the overall operating temperature.

[Wheaters]

"Understood Wheaters but I can't see it making a deal of difference being a bit higher".

Because that's where most of the mayonnaise was forming...without the engine oil being thrown around by three timing gears, I guess the casing isn't being flushed out so the moisture just sits where it condenses