Rapide Oil Leak - Help Please

[youngjohn]

My Rapide has an oil leak which seems to be coming from below the dynamo, it looks like it is coming out around of the rear stud which bolts the dynamo down. Oil is dribbling down the back of the engine and finding its way onto the rear wheel. Could this be overfilling of the gearbox? The level is about 2mm up from the very bottom of the dip stick.
Thanks for any help.

 

[nkt267]

I do not own a twin, but a friend of mine has a Rapide and he found that there is a bolt under thde dynamo that was coming loose. Possibly G34 camplate spindle? I would remove the dynamo for further investigation. It could also be oil finding it's way past the flinger PD28. John

 

[Howard]

Hi

I know it's not easy, but find out where it's coming from first gbox or engine? Try to see what "colour" the oil is. Gearbox oil will stay oil colour, but engine oil will be dirty and probably smell less like oil (if you see what I mean) - compare leaked oil with oil on gbox dip with a dip in the UFM.

G34 (if that's the number - I haven't checked) can let oil out, but not likely in the amounts you seem to be indicating.

Engine oil can come from anywhere (almost) and land where yours does. My guess (only because it's been my problem in years gone by) is where the dynamo seals (or not) but that creates another problem, because its not engine or gearbox oil.

Get a piece of tissue and wipe it in various spots on the engine, there's usually a track you can follow. In my experience with oil leaks, the oil is rarely leaking from where you think.

Good luck.

H

 

[ernie]

Your oil level is 2 mm too high, believe it or not!

 

[Alan J]

Your oil level is 2 mm too high, believe it or not!

Ernie, most of us can't see 2m.m.-the leak is probably from behind the dynamo !?

 

[Tom Gaynor]

I'm sure it isn't the gearbox; and as Howard suggests, oil is almost NEVER leaking from where it appears to be leaking. However it would be easy to draw the stud you think may be the source, paint some Wellseal on it, and replace. Then observe.
Took me a run to Belgium to discover that my root problem was breathing. The engine wasn't breathing well, and was pushing air and oil into the chaincase, where it 1) became atomised into an oil / air mist by a thrashing chain and 2) since pressure will escape if it can, the mist blew out at the dynamo (Alton, actually) where there is a gap. The dynamo has an oil-flinger which is supposed to separate the oil out, but doesn't. Or didn't on MY bike. If it had, IMHO there would be no problem. Once the oil-laden aerosol scented freedom, the oil mist, having survived ordeal by oil-flinger, separated out and disguised itself as an oil leak. The oil dribbled down the back of the engine just as you describe, and in a neat bit of subterfuge familiar to most owners, flowed FORWARD to hide it's origin.
Without opening the can of worms that is breathing, (yet) get a tube of clear (or wood-grain if your tastes run that way) domestic silicone seal from B & Q. Seal the dynamo to the chaincase. This may require a lot of silicone - but it's cheap - and the use of a wet finger to push it in to place. Screwfix sell a cheap degreaser, helps it stick. Using a felt ring 'twixt dynamo and chaincase as a matrix for the silicone works. This operation will do no harm.
What then happens is that if the chaincase IS being pressurised from the crankchamber as the pistons come down (because the breather is inefficient?), the TRAPPED pressure disappears back into the crankchamber as the pistons ascend. There is no net flow from crankchamber to chaincase. (The literature - FYO and ATY - contains complaints that "my chaincase oil level keeps rising".)
In extremis, one can "dye" the engine oil then use UV ("black") light to find out the source of a leak. Then do the same for the gearbox. I bought some. Still have it.
What you don't say is when / how this started. If it has JUST started, I'd check that the timed breather hasn't moved. Or I'd fit a D breather. Vincent didn't drop the timed breather in favour of the D-type in an attempt to make things worse.

 

[ET43]

Youngjohn, I would be disinclined to remove any bolt ( G34 )found under the dynamo as this is the item which holds the camplate pinion ( G33 )in place. At best, unscrew it by a few threads, and there are not many holding in to the crank case, degrease the area and if you must, apply some sealer and tighten the thing up again. Removal of the part MAY allow the camplate pinion to move, = bad news. Vincents have been known to throw oil forward as Tom says, so one trick is to clean the area, dry it off, and dust the area with talcum powder, go for a short run and look at the talc to see if it is stained. This should show you the source of the leak. Not wishing to get in to an argument, to my simple mind, the larger a breather pipe, the more air it will pass and at a lower speed than a small diameter one will, and probably not pick up oil droplets in the process. I am a great believer in the elephants trunk, ugly as it is. Cheers, ET43

 

[youngjohn]

Thanks for all of your advice. I removed the dynamo sprocket and associated bits (loctited a nut on the shaft to keep PD16 on). Now removed, this obviously flings less oil around the top end of the case and seems to have reduced the leak significantly, so I am guessing that the Dynamo needs removal and sealing with silicone against the case. I'm going to try this then check again.

I spent many years chasing leaks on my Venom and have eventually got an (almost) totally leak free bike. Here we go again...!

 

[John Cone]

As much as i don't like silicon sealers i have found this to be the best solution. The trick is to put plenty on the dynamo end plate,offer up the dynamo to the saddle, fit the upper saddle but leave just loose. Assemble the drive side but make sure the sprocket is running in middle of the centre run of the chain and that you have a little backlash. this done tighten the upper saddle ensuring the backlash and sprocket run hasn't altered. Wipe off the excess silicon and leave to set.
PS: Has your dynamo got sealed bearings in?

 

[Howard]

As much as i don't like silicon sealers i have found this to be the best solution. The trick is to put plenty on the dynamo end plate,offer up the dynamo to the saddle, fit the upper saddle but leave just loose. Assemble the drive side but make sure the sprocket is running in middle of the centre run of the chain and that you have a little backlash. this done tighten the upper saddle ensuring the backlash and sprocket run hasn't altered. Wipe off the excess silicon and leave to set.
PS: Has your dynamo got sealed bearings in?

Yep. I don't like SC either, but this works. I assume that your ps is refering to where the oil goes when it can't leak around the dynamo - been there too.

H