Modern Vespa

Howdy,

So I'm doing a little pro-bono fixit job here for a friend here, a dude whose PX200 has been through so many hands in the past year that he's at his wits' end figuring out the cause of his biggest headache as of late: a good 10 or 15 seizures, some soft, some hard, all of them making things worse of course, and the results of which were pretty ugly. So we bored the cylinder and sourced an oversize piston and we're about to put it all back together but...

...we still don't know what the cause was. I had my theories: the carb base was warped, suggesting an air leak; jetting was a little too lean (it was); the autolube had maybe failed; and so on. That last possibility really got me thinking: when I peered down in the inlet port and cranked the kickstarter, all I could see were dry-ass stretches of slightly browned crank web. It was bone dry in there. I'd never seen that before; usually a couple hours after a bike's been sitting, you're still gonna get some 2T slurping and sloshing around, right? Right?

So I started inspecting the fuel pump, and the 'oil canal' on the base of the air box, and confirmed that the base gasket had the requisite oil hole in it, and that all seemed hunky-dory, and then set about cleaning the carb, and then got on Scooterhelp.com just to confirm everything. And then I started learning about the route the oil takes on its way into the carb venturi. And then I compared the Scooterhelp photo with this carb. See attached.

The red arrow points to the hole that the oil allegedly comes out of on its way into the crankcase. Note that there is no corresponding hole in my picture. I tried injecting 2T oil into the intake hole and seeing if it'd drip out anywhere else in or near the venturi / slide, and no dice.

Is it even remotely possible that this bike ran for a hundred kilometres in an unlubricated state? Because if this is a non-autolube carb, that's exactly what it did.

Cheers, and as always, sorry to be so long-winded.

SJ

Sean,
It does look like a non-injector carb. Is it a 24? Original to the bike as far as you know? I just checked 2 old 20/20Ds that seemed identical except for the additional hole into the venturi you've pointed out AND a plug where the hole was drilled from the outside, right next to the mixture screw. I would have thought the carbs would have different model numbers but BOTH are marked 20/20D and they BOTH have the blue arrow hole. Here's a pic:


carb on the right came off an autolube motor

So, maybe NO oil getting thru and you say " ...a good 10 or 15 seizures". I'd say you are a damn good detective!

Easiest/laziest rout: disable the autolube and premix. 8)

Hey, thanks for this. I have to talk to the owner of the bike to get a better handle on its recent history. At first I thought, nahhhhhhh, the thing wouldn't go 10 feet without any oil, but I do have a catastrophic autolube cloggin' in my past, and the bike did a good 10 km's before seizing. I wasn't certain if that was a complete oil blockage or just a fraction of it. Maybe it was the former.

Anyway, first order of business is finding out who goofed. *Somebody* did some work on this bike before the seizures began, and (I'm guessing) through sloppiness mixed up carbs and stuck a non-autolube SI 24 into this rig. I'm *hoping* it was mere sloppiness, at any rate. One thing's certain: he massively over-torqued the carb bolts. Guh!

Next order of business is making an informed decision about what to do about the crank and its bearings. Both sides of the crank feel relatively solid -- I can't detect any play -- but a dozen seizures, some with wheel lockup, and a hundred km's WITH NO OIL WHATSOEVER can't have been very good for any moving part down there. Pomozi boze, as the Serbs say.

Ok just a question -- where did all that oil *go*? When my last autolube got clogged, the oil ended up making a nice big lake in the air box. In this case, I saw a little bit of a mess back there by the mixture screw, but not more than a thimbleful.