Oil leak from gearbox.

Not open for further replies.
Mar 30, 2006

I've owned my bike for about 2 years now. Not many problems so far. Just minor oil leaks, but that's normal right? :D But after putting the bike away for the winter, I noticed quite a lot of gear oil underneath the bike. It had been sitting for a good month. What is most likely to have happened? I thought it might just be a gasket? Any thoughts?

The bike is in storage quite far from here, so I would like to order the needed parts before I go up there.


It is difficult to diagnose from a distance ( a LONG distance), but the most common leak points are the gearbox sprocket seal, the kickstart shaft seal (o-ring), and the gear shift seal (o-ring).
The sprocket seal is a proper seal (040132), while the kickstart and gear shift are common o-rings. These can be improved with quad rings, but for the kick start shaft, the outer cover can be bored for a seal from a Mk3 Commando or simply replace this o-ring with lip seal OEM # 10121 (1" X 1.25" X 0.125") available from most bearing houses.
Also check your oil level in your primary case. If it is over full then you may have a crankshaft seal failure which when the engine wet sumps (and it will!) the oil seeps into the primary and can find it's way out between the clutch and gearbox.
Thanks for quick reply!

The seller of the bike told med that the engine was rebuilt about 5 years ago and almost not been run since. (He was more into vintage Volvos :roll: ) The gearbox was not rebuild. From the colour of the oil it looks like it's from the gearbox, and not from the engine. I will check the primary, but I think and "pray" that the crankshaft seal is not the problem.

But I guess the only solution is to remove the gearbox and look for the problem. I have never done any major repairs on the bike, so I'm a bit afraid. Removal of the gearbox, is it a difficult job?

Good info. My two places are the kickstart shaft (nice drip on exhaust and the "burned in" crust) and the left side of the swing arm. Almost impossible to stop the swing arm leak, as the old big o rings are just too loose and have worn a groove into the tranny cradle. Thicker o rings might help...but the swing arm thing...been really bothering me and I plan a new exhaust very soon and I have visions of a nice burned on crust on the new pipes too...yuck!!!

So....you say there is a better type o ring to install. Any chance of a photo, got an extra in the shop? Be nice to know what I am searching for before I floor the guy at the bearing shop with some off-the-wall request...he already shakes his head when I enter the premises.
Or...some source for them? Did the RGM cat. scan and saw nothing that rang the bell...so that is out. Would be nice to get that leak fixed for more than the usual month that the normal o ring holds up....Thanks!
Jorgenbg, I would first try to ascertain where the oil came from before taking major components like gearboxes out, Why not drain the gearbox and measure the quantity that comes out. If it is the correct amount either put it back in again or take the opportunity to put some fresh oil in. Likewise with the swingarm spindle which in spite of having a grease nipple on the right hand side actually requires thick gear oil. I generally take the nipple out and fill it with a syringe, on pre-cotter pin bikes you should also remove the top locating bolt from the centre of the swing-arm mounting tube to give the oil somewhere to go. On no account lubricate the swingarm with grease. if you ascertain that either of these components are leaking you have the option of topping up the oils and see if there is still a problem under running conditions or at least you have identified the problem. Also as Ron l states Nortons often wet sump after standing for a while and the motor oil drains into the crankcase and then into the primary case. Loosen the crankcase drain plug and see what comes out, it should be firly minimal. Drain the primary case and see what quantity and colour this is also. If it turns out to be motor oil you dont have to do anything other than drain the sump, drain the primary case fill the primary with the correct oil and top the motor oil tank up to the correct level and start the bike to ascertain that all is as it should be. The crank oil seal only leaks because the oil level in the sump is too high and will not generally leak under operation unless you are lazy and start the bike without first draining the crankcase. I'm confident that this problem is the usual one of an incontinent Norton sulking because of inactivity.
If you have the very common leak from the bottom of the oil tank it will look like a gearbox leak so don't assume its the gearbox but check the tank too.
Thanks a lot. This will help me a great deal. I just ordered the anti wet sump valve, so I don't have to worry about crankcase beeing full of oil in the future. Some people say it's ok to start the engine with wet sump(low rpm), others say it's not an armican Harley D. If I got time this weekend I will drain the oil and check for symptoms.

Thanks again.

Here is a link with a diagram and description of quad rings. http://www.marcorubber.com/quad_rings.htm. These tend to give better sealing than ordinary o-rings. I have a variety kit I picked up a few years ago, but most seal and bearing companies should be able to provide them.
As far as your swingarm leak, are you using 90wt or 140wt? Have you tried a light smear of RTV silicone on the o-ring? What is wearing the groove? Certainly not the rubber o-ring. Is the "dust cover" longer than the thickness of the o-ring? The thrust face of the bushing and the o-ring should be the only thing touching the cradle.
Thanks...good picture of this item :D

Will check out the price and such on their website.

On the swing arm....actually, I use 90/140 synthetic. Never have seen a 140 oil and as mine is a bit different set up, than the standard swing arm lube system, question if it would work well it I did find it. Might be too thick. Mine has an old fashitioned "oil cup" on it instead of a grease nipple. Think I got it off some car out of the teens...model T, I think and it was used to fill up and lube something or other. Cup with a cover that you can just fill up. Used to be "grease cups" too, fill with grease and twist a turn before driving, and the grease was forced into the area needing lube...used on chassie parts and water pumps. Sort of forrunner of a grease nipple....anyway.......
I use an oil cup and just fill it up every couple weeks...only problem is the fact the big o rings leak so bad....it all leaks out too fast, not good for the the environment to say the least. The grooves in the cradle, are indeed from the o rings, though. Only solution is much thinker o rings...or X rings, as you mentioned, or to weld and resurface the cradle faces....bummer of a job to get right. Got to find some solution though...hate to see the puddle under the bike. Have seen some other neat systems for lubing the swing arm, reservour with tube to the center bolt etc. All would do just as well as my old oil cup, but if it all leaks out....? Any ideas welcome.
A rubber O-ring that can wear a groove in a steel engine cradle? Anyway, it seem like the only solution is to eliminate the grooves. There are enough cradles around and on eBay, that I think I'd replace the cradle rather than attempt to weld and machine flat and square.
Thanks for the info again....yup.....the o ring did it. Hard to believe, so I'll not be too bent out of shape is you don't believe me....but a nice wide groove in the cradle, just where the o ring sits. Definately not the dish shaped shields that hold the o rings in place. I'd say that years ago when I still had the old favorite loose swing arm shaft and the swing arm did the hoochie choochie all night long, that the dirt and stuff that lodged up there where no 20 year old even bothers to wash his machine, and the side to side action of the o ring did the deed to it. Nice groove, and I don't refer to the latest from BB King either..... Might be best to replace the whole cradle, but as I have limited means...so to say....I will have to hope for some thicker o ring to stop the flow for awhile. Will delve into these x rings and see if there is a method to thier madness. So many things that I'd like to do on the bike and so little "means"..... :cry:

Froze my buns off today and had her out and about today, and she still rocks your socks off. A real rush to drive. I'll get the leaks fixed and the tank and covers spray canned and re decaled , the solo seat paid for and the exhaust I have in the workshop installed....springtime is here!!!!!

Ride safe everyone!!!!
x ring for kickstart shaft......can't find one!

If you read a couple entries above, it is mentioned that there are x rings you can buy to help stop the leak from the kickstart. Looked all over and none that I can find here in Germany...found a source in the states, Marco Rubber, but they only do shipments of minimum 50 bucks. The internet orders are a minimum of ten bucks, but my computer won't seem to eat the code that they require to do this, ten is not TOO much, but still a bit of a snag for a couple of o rings. Anybody got a local source for these things, or a couple in the garage? Anybody willing to be so kind as to throw one or maybe two in the post for me? The leak on the new exhaust, looks like crap, as if the machine didn't have enough leaks already... :wink:

If there is some good samaritan out there with the heart for this...please give me a personal mail and we will figure something out.

I need an "X Ring" with ID 1 inch, OD 1 1/4, thickness, 1/8 inch, Marco part number AS568A-214 see http://www.marcorubber.com/sizingchart.htm
Did you store the bike on the side stand? Mine will let some oil weep down the splines of the output shaft if I leave it on the side stand too long. If that's the case don't worry about it unless you feel you need to. :p
Even better is a genuine lip seal that will fit right in. You need to warm the outer cover and drop out the inner bushing, then clean the bore and insert the seal from the inside. You can use a little RTV silicone if you like. Carefully press the bushing back (I like to drop it in the freezer first) and your done. The seal is a number 10121VM and is available from most bearing houses. No machining necessary. If you can't find it locally, let me know, I think I have a couple spares and I can send you one.
Thanks...both of you!

Drip is on the kickstart, not the output shaft, .... :wink: did see a strange bike though, this weekend....had a kickstand of BOTH sides of the bike so in that case, you could possibly have had a good point... :wink:

Kind of thought that maybe a lip seal was an o-x ring....you must mean a real seal, like on a "rear main" or in a car transmission. Lord...been here too long, that is called a Simmerring here, not that you would nessesarily know that, thought that those seals had another name in the states...lip seal just didn't ring a bell. Anyway....have an extra tranny cover and kickstart shaft, so I will take them to the bearing shop here we we will see if there is a standard "lip seal" available here, sounds like that might be the way to go...anything to get rid of the drip. How does it get inserted, with the numbers towards the outside of the cover? It would have to be put in in the right direction, as those seals will pass oil from one side, and not in the other.... :wink: Must be difficult though, to get the lip-seal out to replace it...or?
Your offer is indeed kind, but I will search here first before I ask you do do that...Thanks!
The seal goes in from the inside of the cover with the "lip" facing toward the gearbox.
Thought so...but it must be a B***h to get it out again.... :wink:

On another subject....

Got my baby though the German vehicle inspection this morning, without a hitch...had to take a deep breath as the inspector took it for a ride to test the brakes....he made it back intact though...

My son had two commandos blast by him yesterday, at the end of the street...10 yards from our front door....very rare here, maybe I will run into them some day....that makes three seen in the last year, and none of them would slow down to find out why my kids were waving and making "stop" signals.....typical commando drivers evidently..... :lol:
Lip seal...not available

Went by the bearing dealer yesterday, and got really nasty looks because I had been there a month ago looking for an "X" ring to fix this drip out of the kickstart...anyway, he gave me the business because I was convinced there must be a metric equivilent to the seal needed, and he was naturally convinced that I was talking through my hat.......(he has a bit to learn yet about using a calulator and converting inch to metric)...even went to the shelf and got the thinnest seal out that he had, and it was admittedly way too thick for the purpose and I came away without the seal in the end anyway. If you know where to get these seals, give me an address in a PM and I will give it a try....Thanks!
If your local bearing house won't help, try a local industrial supply. Here in the states we have McMaster-Carr in Chicago, as well as MSC Supply, Grainger, etc. In fact you can order them via the net. http://www.mcmaster.com/. Just look up "oil seal" and size for a 1" shaft, 1.25" bore and 0.125" thickness.

(McMaster also carries x-rings (quad rings)).
Not open for further replies.