Hitchcocks Forum

Chaps, I am now out and about on the Connie after its top end rebuild (used it to get to work last week...thats another story!) and whilst it appears to be (relatively) leak free, a fair amount of oil is ending up on the chain/rear wheel. After I have parked her up, oil drips down from the chain and sidestand/frame etc. I have done lots of reading up on the whole wet sumping issues and I think understand the basics. The connie as far as I can see has three breathers all on the l/h side, one on the side of the crankcase held in with three bolts which has a pipe that empties itself on the front sprocket/chain area. A small breather/wobbly disc on top of the primary case which never seems to leak and then a breather on top of the crankcase behind the barrels which on mine has a piece of hose going up under the saddle and again dumping itself somewhere around the back wheel...not ideal and pretty sure this isn't correct?

Anyhow, my oil level is about 5/8 up between min and max, could it simply be that I need to drop the oil level a little more as i know from previous posts Mark M has suggested this can often be the cause? If not, what else can be done to help cure/minimise the problem, and do I need to reroute/replace the breather hoses?

Many thanks
Richard

I'd say almost certainly not. Wet sumping is usually associated with oil burning (obvious white/blue smoke in the exhaust, sometimes so bad the plugs foul up,) so I think your problem is breather related. As a first step I think you need to find out which of the breathers the oil is coming from. My suspicion is that it'll be the one from the barrel base, a very common problem. What you need to remember is that by adding the large bore pipe from the top of the tank the Previous Owner has altered the original design. It doesn't matter that the original design was inadequate, but it was a complete package, adding a new breather often means blocking or re-directing one of the old ones. The written material that advocates the large bore pipe from the top of the tank is a little scanty on before and after reports so we can't be sure that all engines behave the same but if I remember correctly the accepted procedure is to block off the barrel base holes altogether. As an alternative you could re-direct it back to the oiltank, this is in fact more or less what the Factory did on the early Interceptors which succeeded the Connie.

REgards Mark

Thanks Mark, I think your right, it is coming from the rear barrel breather but I am going to start her up this afternoon and double check. I am a little confused as to how this breather works (is it simply a hole in the top of the case) and how the hose on mine affects things? Presumably a previous owner simply added on the hose to divert the oil from spraying over the engine area...but you are saying block it off altogether...will the extra pressure not cause the oil to blow somewhere else? If I redirect back to the oiltank, how is that done?

Richard

???? I thought you said the hose came off a fitting on top of the oil tank? What do you mean by "rear barrel breather" then? To repeat what I said, in my experience the breather on the drive side crankcase underneath the left hand barrel is usually the problem one. However, only a careful examination will show which (it might be all!) of the breathers is blowing and then we can suggest an answer...

REgards Mark

Sorry Mark I realise my description is inaccurate, I was doing it from memory. Please see link for a photo of the three breather pipes in question. One on the side, x2 behind the barrel. the green garden hose is the one that goes up under the saddle and vents into the air. All three are blowing oil although the one on the side not as much. In fact, they seem to really start dripping when the engine is turned off, maybe this is lack of vaccuum? Does this make more sense? https://www.flickr.com/photos/55117556@ ... 0306017013

Thanks
richard

Hiya. Mark may correct me here. But that short pipe comimg from the left side of the barrels should enter your oil tank where the green garden hose comes out. That way the crankcases breath to the oil tank. i am not sure what the rear pipe is but i presume its an additional breather from the oil tank. If so it needs to be run up over the back mudguard and terminated by the number plate. At the min it looks like the green garden hose and the pipe behind are doing the same job. I would say your problem is definatly coming from that short pipe on the side breather as its not going where it should. Ed

The problem is that between 1959 and 1965 the various breathers on the drive side changed quite a lot. Your engine looks as if it started with the original Connie/Super Meteor set up and has been modified with an extra breather off the top of the oil tank and although this is similar to early Interceptors the PO hasn't connected it up the same way. Of course we can't see the drive end of the crank and there was also a breather through there into the primary chaincase in some years. Additionally, some years featured a sealed drive side main bearing and then later, no seal! If the crank breathes (either way) into the primary case you need a breather off the case, and that is probably what that fitting on top of the case is. Ed's suggestion is a good way forward, take the barrel base breather to the tank and run the hose right to the back of the bike. That picture is a bit unclear as some of the hoses look disconnected? Finally, the reason the bike drips after standing is that the hoses are holding oil suspended in vapour while running and when you stop it condenses out and gravity takes over. Some people use a one way valve to avoid this but I wouldn't try and confuse things just yet! One last thing (as Colombo would say,) I have been running my Mk1 Inter with an oil filler cap that I found in a box of bits, someone has drilled a 1/8" hole in it and I think this is helping too but it's early days yet.

REgards, Mark

Thank you gentlemen, some good clear advice there. I will start with your suggestions and let you know how I get on. For the purposes of the photo, I simply pulled the end of the hoses out of their location under the toolbox area, they were both resting above the chain venting to the atmosphere.

Hi chaps. To my eyes, the small hose behind the green one looks like it's just going though the chain cover, in which case the barrel-side breather should connect to that pipe and go in there, and the green hose should be extended to the rear number plate area. Or are my eyes deceiving me...?
Stephen

Stephen, I think that is the most likely solution but I was trying to walk Richard through the complex story of original design and guesses at what Previous Owners may have done. Successful diagnosis is only possible when the system under examination is fully understood. How's yours going? I'm reading the Real Classic articles and enjoying them a lot! By the way, are you aware Hitchcocks do a 1 into 4 rocker feed pipe that might have saved you some soldering? Neither was I until someone told me, I fitted one to my Mk1 Interceptor. I have suggested that H's should do a catalogue of modifications and retro fit parts for the Twins too (as well as the Bullets,) but nothing so far!

REgards, Mark