Author Topic: Oil leak from gearbox final drive  (Read 8893 times)

Offline DazSeaton

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Oil leak from gearbox final drive
« on: 27.12. 2011 17:27 »
Hi folks,
Been lying on my garage floor all day looking for a severe oil leak. I am now pretty sure after ruling out the crankshaft breather that the oil is coming from the final drive of the gearbox just behind the sprocket. Having consulted the Haynes manual it says quote:
"The gearbox must be removed from the frame, however, if attention is required to the main bearing, final drive sprocket or the oil seal.
In such cases, the engine unit must be removed first and the clutch"
WOW!!! completely dismantle the bike to change a shaft oil seal. Is this correct? It looks to me as if you can get to the oil seal by removing the clutch and primary drive case. Or is the oil seal fitted from inside the gearbox? see first photo with the oil happily leaking out over the chain.....This is with the bike not having been run and with the rear wheel on a ramp so i can get under it. Had a BIG puddle this morning.
If so looks like a VERY expensive trip to the garage!!!
Also a bit confused as the gearbox oil level is fine. Or does the Gear cluster have a separate oil supply from the kick start end of the gearbox. There is a huge bolt under the magneto which looks like a filler for the gear cluster not shown in the haynes manual, although could be anything. see second photo.
Saying that though the oil leaking out seems like the clean stuff i have just put in!!!
Any volunteers to completely strip down a bike?
Kind regards,
Darren
If you don't start, I'm going to give you a damn good thrashing!!!

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Re: Oil leak from gearbox final drive
« Reply #1 on: 27.12. 2011 18:28 »
Hello Darren. There are a few issues to ponder over. My initial thought is you have overfilled your gearbox. The big nut under the magneto is not the filler. Here's what I would do...... Drain your primary chaincase (remove the lowest cover retaining screw or the hexplug - whichever you have) and drain your gearbox (the drainplug is a hex head on the RHS near the lower mounting bolt). Leave the bike standing for a couple of hours to make sure the leak has stopped (If it hasn't stopped then it's engine oil!). Put the required amount (225cc.) of oil in the primary chaincase - most people use ATF (automatic transmission fluid) which, usefully, is red so if your leak reappears with a red colour you know where it is from! Remove the inspection window on the gearbox (the oval thing on the outside held by two screws) and remove the level plug (rear facing hex head at back of gearbox cover just below level with the kikstart shaft). Pour 1 pint of engine oil into the gearbox inspection window; this should be just sufficient to start to overspill from the level plug. When the excess has drained out of the level hole replace the plug. If the leak is still there then, yes, sounds like gearbox oil seal. And you are right, the seal can be replaced without removing the gearbox.
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Re: Oil leak from gearbox final drive
« Reply #2 on: 27.12. 2011 18:30 »
Hi Darren,
Have you heard of the Haynes book of lies????
Theres no need to remove the engine or gearbox to get at the final drive oil seal
The primary and clutch will suffice!!

BUT
Before you start stripping and dismantling!!! there are more sources than the seal to leak!!!
What grade oil did you put in the gearbox and how much??
The level plug is at the back of the box near the frame gusset , about level with the kickstart shaft
Fill the oil in the oval cover on the r/h side,
the plug on top of your box is not a filler plug but to fit the indexing plunger for a reverse camplate, What letters numbers are stamped on the box?

If the bike is left parked on the sidestand oil will work its way along the sleeve gear bush and downwards!!
Worn bushes will also cause a leak

If the sprocket nut has loosened oil will leak along the splines between sprocket and sleeve gear

The seal is a special BSA part easily available, it is retained by a large circlip

I,m sure someone on the forum in your locality will put you in touch with a competent repairer
(I'm probably too far away from you??)

Regards
John O R


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Re: Oil leak from gearbox final drive
« Reply #3 on: 27.12. 2011 20:19 »
Darren,
               If you use gear oil in the box, you can be sure what you are looking at by the distinctive smell or lack thereof.

Trev.

Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #4 on: 28.12. 2011 12:16 »
Hello Darren. There are a few issues to ponder over. My initial thought is you have overfilled your gearbox. The big nut under the magneto is not the filler. Here's what I would do...... Drain your primary chaincase (remove the lowest cover retaining screw or the hexplug - whichever you have) and drain your gearbox (the drainplug is a hex head on the RHS near the lower mounting bolt). Leave the bike standing for a couple of hours to make sure the leak has stopped (If it hasn't stopped then it's engine oil!). Put the required amount (225cc.) of oil in the primary chaincase - most people use ATF (automatic transmission fluid) which, usefully, is red so if your leak reappears with a red colour you know where it is from! Remove the inspection window on the gearbox (the oval thing on the outside held by two screws) and remove the level plug (rear facing hex head at back of gearbox cover just below level with the kikstart shaft). Pour 1 pint of engine oil into the gearbox inspection window; this should be just sufficient to start to overspill from the level plug. When the excess has drained out of the level hole replace the plug. If the leak is still there then, yes, sounds like gearbox oil seal. And you are right, the seal can be replaced without removing the gearbox.
Hi Macc,
Thanks for the reply. It's definately not the chaincase as it has a belt drive conversion, so there is no oil in there. I also put a drain pipe on the crankcase breather to a container so as I can rule that out. I filled the gearbox as you have described yesterday and the leak got worse for a bit. I am 90% sure its the gearbox oil seal because the oil is clean. I was so glad to see you quote "the seal can be replaced without removing the gearbox". Phew, thats saved many hours of toil. Think I'll take a trip to the Newark show on the 7th of Jan and pick up my bits. Many thanks for the info. cheers. Darren
If you don't start, I'm going to give you a damn good thrashing!!!

1959 BSA Super Rocket 650
2007 Suzuki Bandit 1250 SA

Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #5 on: 28.12. 2011 12:32 »
Hi Darren,
Have you heard of the Haynes book of lies????
Theres no need to remove the engine or gearbox to get at the final drive oil seal
The primary and clutch will suffice!!

BUT
Before you start stripping and dismantling!!! there are more sources than the seal to leak!!!
What grade oil did you put in the gearbox and how much??
The level plug is at the back of the box near the frame gusset , about level with the kickstart shaft
Fill the oil in the oval cover on the r/h side,
the plug on top of your box is not a filler plug but to fit the indexing plunger for a reverse camplate, What letters numbers are stamped on the box?.


If the bike is left parked on the sidestand oil will work its way along the sleeve gear bush and downwards!!
Worn bushes will also cause a leak

If the sprocket nut has loosened oil will leak along the splines between sprocket and sleeve gear

The seal is a special BSA part easily available, it is retained by a large circlip

I,m sure someone on the forum in your locality will put you in touch with a competent repairer
(I'm probably too far away from you??)

Regards
John O R
John,
"the Haynes book of lies". Ha ha, yes I should have known better from past experience!
I put in 20w/50 as it states in the book of lies. I followed the precedure of the oil level plug, so its not overfilled.
An indexing plunger, thats definately not in the book!!!
The letters on the box are STD (which I presume is a standard box) and the letter T
Just had another look and what you state "If the bike is left parked on the sidestand oil will work its way along the sleeve gear bush and downwards!!" is exactly the case.
Think I will chance just changing the seal first before going the whole hog and changing the bushes.
My mate who used to rebuild Vincents for a living has volunteered himself and me to do it. So glad we haven't got the completely dissemble the bike! Thanks for the info, much appreciated.
Darren


If you don't start, I'm going to give you a damn good thrashing!!!

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Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #6 on: 28.12. 2011 12:33 »
Darren,
               If you use gear oil in the box, you can be sure what you are looking at by the distinctive smell or lack thereof.

Trev.

Good tip, thanks!
If you don't start, I'm going to give you a damn good thrashing!!!

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2007 Suzuki Bandit 1250 SA

Offline LJ.

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Re: Oil leak from gearbox final drive
« Reply #7 on: 28.12. 2011 14:07 »
I think 20/50 is a bit thin... probably a straight 50 engine oil might be better... You could also add some grease to thicken it up as well. Why not wait until the oil in gearbox finds its own level before taking on all the work of changing the seal.. especially if your clutch is working nicely.
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #8 on: 28.12. 2011 16:08 »
I think 20/50 is a bit thin... probably a straight 50 engine oil might be better... You could also add a big dollop of grease to thicken it up as well. Why not wait until the oil in gearbox finds its own level before taking on all the work of changing the seal.. especially if your clutch is working nicely.

LJ,
*smile* Never heard of that trick before, adding grease to gearbox oil. Will give it a go.
My main concern is the gearbox running dry, don't like the thought of running it without enough oil in it.
Will go for a short run and see if it loses a significant amount. I like the thought of not dismantling the thing though....
The oil I put in is castrol classic xl 20w/50.
Is this the kind of oil you mention?:
http://www.lkperformance.co.uk/classic-oils/castrol-classic/castrol-classic-gp50-engine-oil-1-gallon/218712
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Re: Oil leak from gearbox final drive
« Reply #9 on: 28.12. 2011 16:51 »
I'm not sure I like the idea of mixing grease and oil, a little blob of grease over the hole in the a bush (particularly a blind bush) will limit lubrication same with the oilways in the layshaft.
there are plenty of additives out there or oils designed for the purpose that will be better than were available when these g/boxes where first used,and there is not too much wrong with those recommended by BSA - evidence the very little wear usually seen in these boxes.
All the best - Bill
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Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #10 on: 28.12. 2011 17:17 »
I'm not sure I like the idea of mixing grease and oil, a little blob of grease over the hole in the a bush (particularly a blind bush) will limit lubrication same with the oilways in the layshaft.
there are plenty of additives out there or oils designed for the purpose that will be better than were available when these g/boxes where first used,and there is not too much wrong with those recommended by BSA - evidence the very little wear usually seen in these boxes.

Good points.
Perhaps I should drain the 20/50 and replace with a 80 or 90 gearbox oil.
Anyone got any suggestions on the oil they use?
Cheers Darren
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Offline LJ.

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Re: Oil leak from gearbox final drive
« Reply #11 on: 28.12. 2011 18:09 »
Brian... you might well be right about adding grease to gearbox oil, I suggested this as WD M20 bikes had a large proportion of grease in their gearboxes. The trouble with thickening up oils then raises the problem in kick starting the bike in cold weather.  *sad2*

Darren... If you decide to use a gearbox oil of such then do not use EP which is Extreme Pressure. There is added sulphur which corrodes the phosphor bronze bushes. Some interesting questions & answers here... http://www.morrislubricants.co.uk/lubricants/company.asp?wp=91

The link to Castrol is exactly the sort I use both engine and gearbox... If you wait until you go to Newark & Notts autojumble then you'll find a guy there under a gazeebo who sells the stuff £20 5 litre., which I think is pretty good value.  ;)
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline DazSeaton

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Re: Oil leak from gearbox final drive
« Reply #12 on: 28.12. 2011 20:09 »
Brian... you might well be right about adding grease to gearbox oil, I suggested this as WD M20 bikes had a large proportion of grease in their gearboxes. The trouble with thickening up oils then raises the problem in kick starting the bike in cold weather.  *sad2*

Darren... If you decide to use a gearbox oil of such then do not use EP which is Extreme Pressure. There is added sulphur which corrodes the phosphor bronze bushes. Some interesting questions & answers here... http://www.morrislubricants.co.uk/lubricants/company.asp?wp=91

The link to Castrol is exactly the sort I use both engine and gearbox... If you wait until you go to Newark & Notts autojumble then you'll find a guy there under a gazeebo who sells the stuff £20 5 litre., which I think is pretty good value.  ;)

I think the castrol GP50 with no grease is the way forward!
Been looking at this old post, couple of people use the EP80/90.
http://www.a7a10.net/forum/index.php/topic,355.0.html
Cheers!
Darren
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Re: Oil leak from gearbox final drive
« Reply #13 on: 28.12. 2011 21:00 »
Darren,
                 I use EP 85 or 90 oil with no issues, in fact it was recommended in the last years of the British Motorcyle industry as we know it.
Interesting that your box is an STD T, this denotes needle roller bearings on the layshaft, if not changed over the years.
You really need to have a good look at the sleeve gear bushes as suggested by others as they tend to wear.
When you get the primary drive out of the way, grasp the main shaft and check for up and down movement [or side to side, it doesn't matter.]
The last time I stripped a car gear box, it had bronze components, and the gear oil didn't seem to be corroding them.
 Trev.

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Re: Oil leak from gearbox final drive
« Reply #14 on: 28.12. 2011 21:24 »
Weve had this conversation before. EP gear oils do not attack bronze bushes, this oil was designed for car gearboxes that have been using bronze synchromesh rings for about 50 years.

I use EP 80/90 in all my gearboxes and have done since I can remember.

Do not use grease. Have you ever noticed when you have had a gearbox apart the layshaft has holes in it and the gears have oil supply holes drilled radially to allow oil to the bearing surfaces, if you use grease it will block these holes and effectively starve a lot of the bearing surfaces of lubrication.

BSA recommended engine oil for the gearboxes but you can safely go to a "thicker" oil.