Modern Vespa

Got a head scratcher for the collective.

It's 100% two-stroke.

I'm thinking it has to be from the autolube pump … but why and how's it getting out?


Scoot runs great. Just rebuilt the engine, all gaskets and seals are brand new. Starts and runs great. No symptoms of any air leaks.

Just this drool of two stroke.

Anybody?

Have you checked the oil tank sight glass or oil line?

Yes. Sight glass is bone dry. Oil line is new, also dry.

have you looked for a leak in the channel between the airbox and cases?

My airbox I think was warped. Leaked from the front by the oil pump gear. Chased that for awhile then got rid of the auto lube. Then took the bike apart to fix the leg shield which hopefully is happening this week. Then I'm trying a new airbox to see if it fixes the issue. I'd prefer to use the auto lube. It's too convenient

You mean like a crack? Haven't pulled the airbox off yet, but like I said, the gasket is new. I looked at everything pretty closely before I put it back together just a few weeks ago and everything looked normal.

And the oil pools overnight. There shouldn't be any oil flowing to that channel when the engine isn't running.

Thx, but how would oil get under the airbox when the bike isn't running?

Ahh...I missed that bit. It's pretty much gotta be the oil tank, then. have you pulled the tank to inspect it yet?

If it's leaking without running, it's gotta be the oil tank

I suggest to pull the tank and hang it up with the end of the oil line plugged, then fill the oil tank.

And just to speed up the process, you can blow in the oil hole to force the oil out. Just don't take any pictures or tell anyone!

I'll check, but don't see how it could the oil reservoir. The reservoir sits way down in the frame, below the fuel tank and there's 2 stroke all over the top of the case, and on the clutch cover.

It could still be from under the air box and just slowly making a mess from the top down.

I had a P200 do that recently. First a drop or two, then a few more, then a puddle. I pulled the carb and box, cleaned everything up, and new gaskets. Tightened the carb box down tight, then torqued the carb, and all seemed to clear itself up and no more leak. I took extra precaution to line the carb box gasket up too ..

Oh, and before I took the carb and air box off, I took it to the car wash and blasted it clean so I could tell a bit better where the oil was coming from...

Hope this helps. I'm curious to see where it's coming from....

If the oil line is removed and plugged before leaving it overnight, then at least you'll know if it's box or tank.

What is it that 'seals' the 2 stroke oil when the engine is stopped normally? Is it the clearance between the the auto-lube pump gear and casing it runs in?

I'm curious as if the oil level in the reservoir was above the carb, you may still have the leak when the engine is stopped?

I had a similar albeit smaller leak which like others have suggested, ended up being resolved by pulling the airbox, cleaning, new gasket and retorquing.

That I could never figure out. So I just removed it all cause I wanted to ride rather than tinker.

I had the same issue you did with it leaking down the clutch cover as well. Cleaned it all up and powdered the engine case around the bottom of the airbox and the clutch cover etc and waited. Was 100% starting under the air box at the small corner at the end.

Also had all new gaskets (multiple times) and passed my air leak tests. I was pulling my hair out trying to figure it out.

Bingo. Doing this now.

The way I understand it, oil gets pumped UP from the reservoir when the autolube gears turn. The oil is below the air box - it's not delivered by gravity.

The only way it could drool out of the airbox with the engine not running is if it was being siphoned up somehow into the oiler, running thru the oiler, and then leaking past the gasket. That's a lot of failure.

Thx. I guess we'll find out.

Good luck. My tank is an aux tank in the glove box. Was easy to rule that out in my case.

Little update …

Drooling stopped with the oil line disconnected. So, best I could tell, the 2-stroke was somehow making its way thru the oiler and dripping out from under the back corner of the airbox on the wheelside. Why exactly, I don't know. Box wasn't loose. Might have something to do with the amount of oil in the reservoir and the scoot being on the side stand. Defective gasket maybe? I can't explain it.

Cleaned everything up, squeaky clean, put a new o-ring on the autolube shaft, replaced the airbox and carb gaskets and snugged everything down. Drippage seems to have stopped for now. We'll keep an eye on it.

Thx all.

Did you check the little passage right next to where the oil pump drive shaft pokes out of the case? It's in the back corner on the wheel side. When I did my engine rebuild that passage was clogged with black sludge. I would think that passage returns gear oil and not 2stroke oil.

Hec

Thanks, good tip, but that passage doesn't exist on pre-P series oil injected scoots (Rally, Sprint & Super). They use a slightly different autolube system - different airbox, different pump.


https://www.scooterhelp.com/tips/engine/oil.mixer.old.vespa.html

I'm gonna check mine. That'd make sense as my issue since the leak was coming from that spot.

That is literally a "Back Passage"

Another possible source of the leak is the metal oil pipe threaded fitting into the top of the pump. That fitting becomes loose from vibration, as I experienced on mine. I used teflon tape on the threads, and it still became loose after awhile; I could see green 2T oil oozing around the pipe. Ultimately, I sealed that fitting with blue locktite, and that seemed to prevent loosening. However, some oil was still coming out. In the end, I sealed the top of the fitting around the pipe with permatex sealant, and that finally ended the leak.

Same procedure with the same steps and ultimately solution on my T5, except that I used reinzosil instead of permatex.