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[TONUPBOY]

Hello, folks! I'm new to the forum; just purchased a 2006 Bullet 500 a couple months ago. Since then, I've only gotten to ride it a handful of times, as I've been busy doing a 1950's cafe conversion which turned into a major job (I spent two weekends simplifying the wiring harness and getting rid of components I deemed unnecessary).

Anyway... enough back-story. I've had an elusive oil leak, with nearly a tablespoon of oil sitting on top of the crankcase after my few short jaunts. I've finally traced the leak to the distributor (or contact breaker, if you prefer) shaft, where it meets the timing chest. I realize there is another thread that addresses this issue (http://www.hitchcocksmotorcycles.com/fo ... ost_119468), but I'd like to ask a couple additional questions and take the topic a little further if I may.

My bike has the threaded nipple coming from the oil tank. The previous owner was a machinist and had welded his own "catch can" of sorts, with lines leading from both the timing chest and the aforementioned oil tank nipple up to the can, and terminating with a third line running the length of the rear fender and out a duckbill fitting. The oil leak I described was present at this time, prior to any changes that I made to the breather system. Per an article I read, I decided I'd try to return the breather system to what you'd find on bikes of old-- a single duckbill breather hose from the crankcase, while blocking off the return line to the timing chest. Was blocking that line a foolish move on my part? Or is it safe to assume that the holes which return the oil from the timing chest to the oil tank are probably blocked, and I ought to simply remove the timing chest cover and have a look? I was hoping to avoid that at all costs, but I guess a man's got to do what a man's got to do...

As far as I know, the oil pump is stock. This may or may not be helpful to diagnosis, but it should be noted that the oil coming from the offending area is a sporadic squirt or mist, not a gush.

Any advice would be greatly appreciated. Thanks in advance!

[Adrian]

A forum search for breather and breather modifications will show you how much time has been spent on this subject. If you are getting excess pressure in the timing chest it could well be what's driving the leak between the contact breaker drive and the back of the timing chest. Is there also any oil leaking past the oil seal behind the points cover?



Whipping the timing cover off should be a dread-free operation, just have a bowl ready to catch the oil when it pours out. Have a new gasket ready if the old one shreds, remove the timing cover screws, gently tap the alloy tabs which later timing covers have from behind and it should come off fairly easily, it's unlikely you'll disturb the valve or ignition timing.



The oil return from the timing chest to the oil tank is the hole between the two idler pinion shafts, just in front of the fixing screw hole as shown here:



http://accessories.hitchcocksmotorcycle ... d265418473



You should be able to see if it's free without disturbing the idler gears, though you can always mark their teeth position with reference to each other and he other gears in case you do need to remove them, though if you're fitting a new gasket between the contact breaker drive, the latter's pinion will have to come off anyway, with the ignition re-timed when it all goes back on.



If the oil tank isn't breathing freely that will cause a pressure back-up in the timing chest, so whatever breather/catch can setup is used, it MUST vent freely. You can add extra breathers to the rocker covers if needed.



A.

[TONUPBOY]

Thank you, Adrian, for your prompt and well-thought-out reply. I just wanted to make sure the holes that go from the oil tank to the timing chest are sufficient to regulate timing chest pressure-- that the timing chest return line doesn't also serve to aid in the release of said pressure, and plugging it is has exacerbated things. I suspect that since this same set-up has been used by many others without incident, that's probably not the case. My breather hose is clear, so I've got a constant visual on it; there's quite a bit of condensate (as to be expected), but it's not blocked in any way.

[stinkwheel]

Here are those return holes from the timing chest as viewed from the oil tank side. Also neatly shows the oil tank breather stub, which they are very close to and where the resting oil level sits on the dipstick.

[TONUPBOY]

Thanks, stinkwheel; it's really nice to have a visual reference of what's going on in there.

Oddly enough, this afternoon when I unblocked the timing chest breather and vented to the atmosphere, the oil leak appeared to resolve itself. I've decided I'm going to see if I can pick up on a "T" fitting and connect both the oil tank and timing chest breather stubs simultaneously, terminating in a check valve (instead of the duck bill I have currently, which I feel could be prone to gumming up, affecting it's operation).

I figured I could do what numerous others have done by plugging off the timing chest breather with no ill effects, but I guess that simply wasn't the case.

[stinkwheel]

It's not unheard of to put a breather on the exhaust rocker cover on brit bikes, not just enfields. I'm seriously considering doing this on my 612 when I see a suitably cheap one to ruin come up on ebay. I'm pretty sure my 350 gets a certain amount of blowpast.



I see no problem with doing what you propose though. If there's positive pressure anywhere it should go out up the hose. I suppose it could breathe from one compartment to the other but it can do that anyway via the existing holes.

[PeteF]

If I understand you correctly you think the pipe coming out of the back of the timing chest is a breather. This is not the case. It's there to supposedly drain the original catch can. This is something it didn't do very well as the pressure in the timing chest, which is the same as the main breather, prevented the catch can draining. On the original pipework there was a non return valve in the pipe from the timing chest to the catch can so the pressure in the timing chest couldn't vent to the catch can. This valve invariably got stuck up with oily emulsion and stopped the catch can system working properly. Many people ditch the catch can system altogether and seal this pipe off altogether. The main engine breather is vertical out of the top of the oil "tank" and this is then led to under the bike or to the back.

[TONUPBOY]

Thanks for enlightening me, Pete. I think I'll simply take a short section of hose and route it from the timing chest nipple to the stub under the cylinder barrel (the original breather) so it appears somewhat original, and even normal to someone who doesn't know any better. I hate using plugs and caps, as I find them rather unsightly. Maybe I'll scour the forums and see what others have done. I'm open to ideas, too!

[PeteF]

If your bike still has the main breather at the base of the cylinder you can't connect that to the timing chest or you'll have no breather at all. Later models had a breather coming out of the top of the oil tank. If you have both for some reason I would use the one at the cylinder. You could then short circuit the oil tank and timing chest.

[PeteF]

Have a read of this;
BREATHERS