Transmission oil leak

Hey folks, my first technical post so thanks in advance for reply’s. I have a 2003 Swing with 67k miles that I recently bought from a family member that put 50k of the miles on it. I discovered that after I ride and park bike for the evening (on center stand) that the next morning there is a couple drops of oil on garage floor. I took the plastic panels off and it appears that oil is coming from around the square looking hole in the seem underneath housing. I removed the filler bolt to check the level and oil poured out. I didn’t know at the time that oil coming out meant overfill so I tried to get the bolt back in as fast as possible before losing too much oil. Now that I know that it evidently had too much oil do you think that may be why the oil may be leaking in small amounts from seam hole? Should I remove fill bolt again and let drain some more? Is there possibly a bigger problem than just overfill? The previous owner was meticulous about keeping everything serviced and gave me all the service and parts replacement dates he had.

I do have a question- when you checked the fill bolt, was the SW on the center stand? If oil did in fact come out via the filler, it sounds as if it’s is overfilled (but I’d be surprised if it’s even possible to overfill the rear drive — how do you fill it up then get the bolt in quickly??).

Yes, was on center stand and oil pooled quickly and profusely on the floor before I could cram bolt back in and get it tight enough to slow the pooling so obviously somehow it was overfilled but I don’t know either how that could happen.

I have come across this problem in the past, I remember seeing an old generic YouTube about scooter maintenance where they laid the scooter over on its side and then filled the final transmission up.
My Suzuki burgman had way to much oil in the final drive, so I drained and re-filled it correctly on the centre stand.

Hope this helps.

Be safe, be seen!

The little bit of oil that it drips doesn’t bother me and it usually doesn’t drip until after I have brought it back from a ride. My big question is if it were to be a seal leak should I get it replaced immediately? If I don’t get it replaced and continue to ride it what’s the most that would happen?

I had a similar leak on my first swing '03 model. I found it was the drive side crankcase oil seal, oil migrated down the slope of the belt enclosure and appeared as final drive leak.

Marvincon, did you replace the seal? If so was it an expensive and intense job? I’m thinking of just riding it and cleaning the oil off as necessary until it breaks. I recently bought it for 2 grand which was probably a little much but I do know that the previous owner had recently done major maintenance stuff on it and I felt good about it but now I don’t want to sink anymore money than I have to in it because of it’s age and high mileage.

The clutch bell has to be removed and the whole of the RH swing arm also that allows the drive belt housing to be removed which gives access to the crankcase oil seal. I also replaced the final drive shaft oil seal as I purchased it anyway. It's not an either expensive or difficult job, I'm no expert mechanic just like working on the swing. I think the crankcase seal was £16 (British Pounds).
The leak didn't get onto the belt in my case but if the leak was heavy it could do. The leak may not be this seal, just letting you know my experience.

Like JohnyC said, service the gearbox correctly (or just remove the "Fill" bolt let it drain) clean area, etc. and see what happens after a few days.

I replaced all the gearbox seals a few years ago, had a small leak out of gearbox bottom drain/weep hole, not a hard job for a mechanically inclined DIY, but it's a big job. Lots of disassembly required.
I have a few pics, if needed.

I over filled it once and it cost me a belt, leaked inside the case and soaked everything. Before you do anything set the oil to proper level and see if leak persists. Put it on center stand remove fill bolt and walk away till it stops dripping out also check the vent tube.

Never had another problem with the correct oil level.

How do I check the vent tube, do I blow air in it or take it out and clean? Not sure of the process.

StixNC wrote:

How do I check the vent tube, do I blow air in it or take it out and clean? Not sure of the process.

Based on what "Mech 1"said, you really need to open the belt area and investigate further, plenty videos on YouTube on replacing belt, seals, etc., etc.

Some years ago my friend overfilled his engine oil on his 'brand new' Kawasaki Z250. We were in convoy on a motorway when he started signalling that he had trouble. His exhausts were smoking like a 2-stroke.

We pulled in and I asked if he had done anything to the bike since last riding it. He said, "yes, of course, I put half-a-litre of engine oil in". When i asked why and "did you check the dipstick"?, he went a bit quiet.

Anyway, we removed the excess oil by tipping the bike over and got it somewhere near the dipstick guide. Point is, the pressure from the excess oil in the crankcase must have been forcing oil past the piston rings. The bike went along fine for years after that.

I opened the belt area and it was nasty with oil and grunge. There was no obvious points that I could see where oil would be coming from but the vent tube was covered in gunk and oil all the way back. I blowed in the tube with mouth and it felt that there was resistance although I’m not sure if resistance is normal or whether air should have freely blown through. I cleaned everything up and buttoned it back and took for a ride then brought back and set on center stand all day and night without any drip. Even though there’s not a drip I ran my finger around the square weep hole and noticed a bit of oil on my finger. If the vent tube is bad will it cause oil to leak into the belt housing and is there a way to replace the vent tube if necessary? Thanks

Pulled the vent tube off the nipple and cleaned it up and was able to blow air through the tube. Finally discovered that the oil drip is coming from behind the front belt pulley.