Author Topic: crank/drive side oil leak  (Read 859 times)

Offline Slippery Sam

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crank/drive side oil leak
« on: 17.05. 2017 08:40 »
Looking for a couple of pointers.
I have a small leak for which I've had the sump plate off and re-sealed twice now and have just discovered the oil is coming from the joint of the primary back plate where it meets the crank case.
I quickly opened the outer primary case (didn't take the foot rest off so could only peer/feel inside).  I have a BNR belt drive running dry and there was no sign of oil inside the primary.  Next thought was oil breather - I have no pipe or fitting in there just the hole in the crank case.  Again bone dry.  I have a brand new crank oil seal and spacer piece.  However I do suspect this is probably where the oil is escaping.
So next job will be strip off the primary (I would like to re-do it in any case as I wasn't entirely happy with the belt alignment so will adjust the crank sprocket distance piece while I'm there).
So my couple of questions:
Can the crank seal leak and escape between the primary inner and the crank? (without getting into the primary?)
Could my breather be blocked and it's internal pressure causing this?
When I come to re-tightening the Crank sprocket nut and clutch centre - should I be using a tool or a special method for holding everything?  - wasn't that happy with the methods I used last time.
Could it be the inner case mounting bolts? are they all the way through the crank case?
Does the oils seal spacer piece fit with the chamfer to the outside?
I have a new seal and spacer sitting so ready to do the job (might be in to parts if I have to get a distance piece made) - however might not start it till next week - I have a DVLA (SGS) inspection next Thursday so want it complete and running for that.
Just getting prepared in case I need to buy or make a tool - or look out any other parts that might be causing it.
Will report back with findings.
cheers Raymond.
BSA A10 Cafe Racer project

Online Klaus

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Re: crank/drive side oil leak
« Reply #1 on: 17.05. 2017 09:23 »
Hy Raymond,

The 5 bolds were the primary is fixed to the crankcase are the only possibility where the Oil can escape.
Be sure the distanceplate is sealed with two gasgets, a little silicone by fiting  is recomented.

The BNR Kit is with the spacers are you sure they are the right way. They are normaly signed with rear and front.
Please do not over tightend the belt. If you can twist the belt in nearly 90 degrees angle the tension ist corrcet.
cheers Klaus

If you think, everything is under control, you are not fast enought.

Offline duTch

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Re: crank/drive side oil leak
« Reply #2 on: 17.05. 2017 09:41 »
 Hiya SS/Ramondo- I'm of of touch with S/A models,  but from memory the chamber goes in (no doubt someone will spey that out), but one thing S/A's have on common with Plunger engines is the rear two bolts. 
 On S/A's they hold the inner case,  but on Plumbers they hold the P/Chain tensioner, and on both cases  (no pun intended) they go right through, so could be a source of leakage.
 When i last tightened my crank/cush nut, I utilized this by screwing in a longer bolt to lock the Web as it engaged (crank rotating clockwise from drive side),  and it worked ok for me,  but I think was met with scepticism or uncertainty...I'll let you work that one out
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy

Online JulianS

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Re: crank/drive side oil leak
« Reply #3 on: 17.05. 2017 10:16 »
If the crankcase seal leaks it will leak into the primary  first, nowhere else for it to go first.

The 3 external front primary chaincase screws all go through to the inside of crankcase.

The 2 internal primary chaincase bolts also go right through (I loctite these 2 to keep them in and seal the threads to oli)

The leak in the joint is almost always via these screws/bolts

I seal the spacer and gaskets (some parts books show only one gasket but it should be one each side of spacer) between chaincase and crankacase with silicone, but undoing the front screws to access primary drive can loosen the joint at the front and allow oil to seep. Sometimes you may find oil at the heads of the front screws.

The oil seal spacer goes with chamfer towards the bearing.

I doubt the breather is blocked - if it was you would have a seriously leaking engine in many joints.

Online orabanda

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Re: crank/drive side oil leak
« Reply #4 on: 17.05. 2017 10:39 »
I also use an o-ring (small x-section; trying to remember - might be 1/16") inside the chamfer of the hardened crankshaft spacer to eliminate leakage tbetween the shaft & spacer bore.

Offline Slippery Sam

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Re: crank/drive side oil leak
« Reply #5 on: 17.05. 2017 12:50 »
Great guys - Guess I know where I'm looking now.
I have absolutely no sealing on either the inner or outer case bolts nor the gaskets and thin space between the crank and inner cases.  Sounding hopeful of a fix.
On the breather - I will check it is clear and will fit the correct fittings, rather than just a hole, when I have the primary inner case off.  I suspect this is working as I don't have any other problems (can always check it the next time I run it and see what it's like in operation - bike is up on the bench again while tinkering with the primary).
I'll do some measurements and will double check the BNR instructions/diagrams - but the belt when square on the front pulley runs near the outer edge of the clutch pulley so unless I find something that allows me to get the front pulley 1/8" closer to the crank, I'll make a new spacer 1/8" thinner?  I will check the clutch basket assembly too in case I missed a spacer or something there (that would fix it too).
For crank and clutch basket nut tightening - we'll see how tight they are with the method I used to put them on - but will maybe get inventive (I have other clutch basket holding tools for japanese bikes so might re-create one of those (actually one is a Suzuki version - might get really lucky?? - are some of the modified clutches available not Suzuki items???)

Thanks again guys - another day another BSA lesson - love it :-)

Cheers Raymond.
BSA A10 Cafe Racer project