Modern Vespa

I've been chasing a leak on a PX200e engine and am pretty sure it is coming from under the carb box. I have replaced the carb gaskets once already so today I took it apart again but this time I spent some extra time surfacing the carb box.

I also wanted a little tougher gasket so I decided to try my hand at cutting a new gasket for the seal between the carb filter box and engine case. It was a bit of a tedious process but in the end, I successfully scanned, scaled and cut a new gasket using my laser engraver/cutter.

I guess time will tell if my fix worked this time.

https://youtu.be/yn4pKVeQm-0 (Video of the laser doing it's thing)

1. Have you looked inside the carb box to see if there is a puddle of fuel/oil at the back corner? Normally a leak between the box and the motor would be more of an air leak issue - racing of motor due to lean running conditions - rather than drip. Rich mixture at some point of throttle could be causing some blow back of premix into the air box - which is finding its way out near the rubber seal in your photo.
2. Im going to say 66 mustang coup. Tough to tell tho with loose fit of cover. Long shot: Corvair.

No fuel that I noticed in fact the inside of the box was pretty dry this go round. It's going to be a couple of weeks before I get it back on the ground but it sounds like from your comments that I may still be chasing the leak.

Your "long shot" was correct. My other air cooled vehicle is a 1962 Corvair.

Thanks!

Keep in mind that the the carb, and case are milled flat and the sheet metal box should also be perfectly flat as well. The original gaskets were quite thin and relatively stiff. The components should pretty much seal even without a gasket. A thicker gasket can compress under the bolts and cause the carb base to distort. What I am saying is that you don't need a tougher gasket but better mating surfaces between the components.

Are you sure it's fuel and 2T mix and not gearbox oil? The photo appears to show pitting where the two case halves join, and it's difficult to see the gasket. You would normally see a little 'overhang' of gasket paper, often blue, brown or green.

I did have some unevenness on the bottom of the carb box which I fixed by lapping the surface. The replacement gasket I made is still a very thin gasket, I just used a better quality of gasket paper. I completely agree that the flatness of the mating surfaces is the most important aspect of getting a good seal.

Thanks!

I'm pretty sure that this engine has been opened up in the recent past and all of the gaskets are of the basic, all brown paper cheap kit style gaskets.

I actually believe that it is leaking crankcase oil. Not smelling any fuel and the color is more CC that 2T oil. I think the pitting you are seeing in the pic is actually just dirt and oil. I was just assuming that oil could be escaping from between the box and engine case in the area under the oil injection pump but that could be an incorrect assumption on my part. I just figured while I have it apart again, I'm going to recondition and reseal all of the mating surfaces. I did also retorque the case bolts and found that the outer bolts were spot on while the inner bolts were a little under spec.

Here is another picture taken after cleaning.

Thanks for your input as I need all the help I can get. Ask me anything about building a Corvair engine and I'm right there but but when it comes to these vintage style Vespa engines, I am a complete noob.