Gear Box oil leak

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Johnnymac

Johnnymac

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Oct 8, 2011
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Guys, I am having some issues with leaks coming from the main oil seal area on the gearbox of my Combat. Being that I'm not a master mechanic, I took my bike to my local cycle mechanic. I had all the oil seals and gaskets that they needed to replace the crankcase, gearbox seals including the primary O-Ring and the gasket for the inner -primary/crank case.

I picked it up yesterday only to get home to find gear oil seeping out, making its way down my primary and on to my header. I went right back up to the shop and this time watched him as he replaced the gearbox seal again (not because I distrusted him... but because I wanted to learn). Took him a few hours... rode the bike home, and wouldn't you know it, gear oil is oozing out of the gearbox again....

I have called the shop and the mechanic is at a loss. He has no idea what the issue is.... we have replaced the main oil seal twice now. Part #9 on this Andover Norton diagram http://www.oldbritts.com/1972_g5.html The mechanic has done this on several nortons before in the past with no problems....

What are we missing here? Why would oil be seeping out of the gearbox there?

Thanks for your help!
 
Is this leakage comfirmed to be coming from this seal?
It so.....
1. trashes sleeve gear/seal surface?
2. wrong seal?
3. seal reversed?
4. ?
 
pvisseriii said:
Is this leakage comfirmed to be coming from this seal?
Click to expand...

+1 on that and in addition,
- what fluid are you using in the primary?
- has there been careful filling/monitoring of the levels in the tranny and the primary (if you're also using gear oil there)?
 
Could be pressure related. When the 'box gets hot it may not be able to vent. A lot of people drill a tiny hole in the inspection cover. See the Old Britts technical article under Gear Box, Clutch, etc.
 
Yes, saw that it was coming from that area... where the shaft exits the gearbox. The first seal we thought was leaking because the spring was off inside the seal lip... he was UBER careful installing the seal the second time. They were both new seals, correct, and free from any defects that we saw. I saw that he did grease up the seal before installing it... but assume that is correct.

I am using 90w Hypoid Gearoil in the gearbox.

ATF in the primary.
 
Anglophile said:
Could be pressure related. When the 'box gets hot it may not be able to vent. A lot of people drill a tiny hole in the inspection cover. See the Old Britts technical article under Gear Box, Clutch, etc.
Click to expand...

There is a tiny vent hole in my gearbox inspection cover. Also, the first time that it leaked.... it seeped out over night when the gearbox was cool.
 
I forgot to mention, when the bike is upright.... at the shop it wasn't leaking. (I don't have a center stand) But when I leave it over night on the side stand, it seeps out the left side of the tranny.
 
Just a thought, is the gearbox possibly overfilled with gear oil?

Pull the little inspection cover and look in there to see that the level is no higher than the bottom of the left
side "level" bolt, maybe in the middle of the big spring you can see in there.

Much higher and it can drain through to the left side, and if it doing that then it may be coming over along the clutch rod and in to your clutch and hence from there filling in to the primary, good time also to put on Dyno Dave's little O ring clutch rod seal.
 
Just a thought but how about the seal for the alt wiring which passes through the backside of the primary.
Since it has ATF it would be red fluid but just a thought.
 
1up3down said:
Just a thought, is the gearbox possibly overfilled with gear oil?

Pull the little inspection cover and look in there to see that the level is no higher than the bottom of the left
side "level" bolt, maybe in the middle of the big spring you can see in there.

Much higher and it can drain through to the left side, and if it doing that then it may be coming over along the clutch rod and in to your clutch and hence from there filling in to the primary, good time also to put on Dyno Dave's little O ring clutch rod seal.
Click to expand...


How much oil does the gearbox take? I just had a look... and it was above the level hole. I pulled off 5+ ounces before it got below the plug......

And here is the thing that really pisses me off..... When I went to put my bike on the side stand... .the f***ing side stand bolt snapped and the bike fell on to the side peg. I was on the right side of the bike and had oil all over my hand and couldn't keep her up. Side peg is a bit bent, but otherwise everything is OK. Thank GOD no damage... but it could have been disastrous.
 
Been there dude.
Coulda been worse, the dog coulda been sleeping on the other side.
 
It seems clearly that the gear box WAS overfilled with oil.

Did your ace mechanic not have access to a workshop manual to find out how much to put in there?

Just took a wild guess of how much perhaps?

Sorry that had to happen to you, fortunately no real harm done other than much anxiety!
 
Thanks for all the responses guys. Now that the gear oil is at a respectable level... I will need to get the side stand on before I take her for a spin.... I am so relieved that there was no damage when the bike fell over! I will report back if the lower oil level solved the leak issue. Having it upright on the bike jack all night didn't result in any leaks so fingers crossed.
 
See if you can get a grade 8 bolt for that stand. Plus if you can get one that's not fully threaded, they're stronger. Better yet a hardened pin with drillings and grub screws.

Dave
69S
 
My engine sat and wet sumped for a long enough time for oil to seep into the Primary so when I first road it, it leaked and I thought the gearbox or other seal had gone bad. Thanks to forum wisedome I learned check & drain any excess oil in the primary if it wetsumped & sat for very long. Sorry about your bike falling over but & hope your gearbox was just to full. If you don't have a work shop manual to learn the fluid levels from that should be your next purchase. At least go to the Forum index & read/download it from there. Good luck, Glenn
 
After finding out what the natural level should be in gearbox I now look down into the inspection/fill cover to fill oil to just covering the cogs top seen deep down inside. Thankgoodness me stored wet sumpers don't spill into the primary, so far.
Commando's are a thinking man's bike with too much time and money to put into something more practical useful that lasts long. There ain't no way to seal the sleeve gear bush at end of shaft, just an open slot if oiled enough to reach it.
 
Well, I got the kickstand back on.... I never realized how bent that bolt must have been. My bike is much more upright! Lowering the gear oil level to the appropriate level, and have a stand that doesn't tilt my bike to a 45 degree angle stopped the gearbox leak!! I have ridden it for about 15 miles and not a drop of gear oil is leaking now. (Knock on wood). I have now ordered a centerstand. I think they are probably better then the sidestand.

Thanks you guys for all your help!!
 
Johnnymac said:
I have now ordered a centerstand. I think they are probably better then the sidestand.
Click to expand...

I have both. I use the side stand the most and use the center stand to work on the bike.
Nothing like the tripping hazard of a side stand to give the bike it's gangsta lean.
 
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