Modern Vespa

I took the engine out of my px 200 for the first time a few weeks ago and have just got it back in and all cabled up. It started but is burning a lot of oil - belching smoke big time for several minutes before I shut it off.

I took the engine out to give it a serious clean (ten years of gunk on it from previous owners) and change the rear shock which had given up. While it was out I removed the head and the barrel to clean carbon off the head and the piston head. Looked at rings and barrel which seemed ok, no real scoring or sign of wear.

Engine ran fine before I touched it (duh!) I am assumng its not just fuel and oil separating in the fueltank (the oil pump has been disabled - I premix) becasue they've been standing for a couple of months? and I've seriously buggered something up like a seal.....any suggestions?

I don't know how you could mess up a seal from just cleaning it.

Does it run smoky like ...forever? Or was it just a lot of smoke for a while until it warmed up?

my first guess is the clutch side seal

did you drain the oil before removal and then replace once remounted?

is the smoke a very white smoke screen kinda smoke?

remember that 2t smoke has a distinctly different smell than gear oil smoke

a little smoke is normal(2t usually)
alota smoke is not normal(seal)

It runs smoky for quite a few minutes - shows no sign of stopping. Smoke is whitish, not dark. Will try again and give it a sniff to see if it has distinctive two stroke smell....I drained thw old gear oil out before I removed the unit.

Before I took the engine out it would sometimes puff a bit of smoke when I started on the choke but it would clear very quickly - seemd normal. Now it is like the tank is full of oil...

But did it keep smoking after you rode it longer? Like for a tank or so?

If it's white smoke for longer than it takes the bike to warm up, it's likely clutchside seal.

If it's just a lot of smoke when you first start your bike, it's a bad needle valve.

thanks for all the advice.

Well I ran the bike for 5 minutes or so and its a really thick cloud of smoke so riding around for a tank load isn't really an option. I pulled the plug and it has a lot of oil on it. I guess the removal of the engine must have disturbed it, or it was on its way out anyway....I can't think of anything I did that could have inadvertently caused it

As the bike is parked in my front yard I was half wondering if it was worth draining the tank and refilling in case some low life had chucked something in one night - but that seems pretty far fetched

Is there any other symptom or way of establishing if its a clutch side seal?

Drain your case oil and see if it smells like gas...or if there's a lot of it ...or if it's really thin like water. ( because the gas has thinned out the normally thick case oil )

So thats why mine stopped doing that after a carb rebuild. Learn something every day!

Thanks Eric - will drain it at the weekend and see what comes out.

I can't remember my O level chemistry but presumably if I stand the mix in a measuring glass/vessel it will naturally separate as well...

You don't need to drain the whole case, just unscrew the drain plug enough for it to leak on your fingers or into a little cup, close it up, and smell/feel what came out. It's obvious if it smells like gas, the oil itself is pretty inert smelling. Takes a minute or two. No need to let it separate, especially since gasoline is a very good solvent for hydrophobic molecules like in oil and you might be waiting a LONG time.

Sometimes decoking can leave a little bit of debris in the combustion chamber which may smoke until it's burnt/blown out. Riding the bike (at higher revs than idle) will do it faster. Seafoam will cause the same thing to happen, but that's also partly due to the seafoam mixture itself burning.

I've ridden with my clutch-side seal busted until I could fix it, keep your gear oil topped up, if it starts revving high then adjust your idle speed by slowing pulling your choke out. Better to fix it sooner than later, though.

couldn't wait until the weekend...came up with an excuse to work at home today and drained the oil.

Now I can tell adnams ale from london pride by smell, but I'm not so sure with my oils! Never thought getting into scooters would lead to testing my powers smell to distinguish oil bouquets

Anyway I drained about 200ml of pretty clean viscous liquid that has a slight butterscotch smell to it. Sniffed side by side with new gear oil I'd say it was pretty much the same in smell and viscosity and not tainted by fuel - so does that rule out a clutch seal leak?

When I filled it I guess I used a bit more than 200ml but i may have lost some while trying to fill it. How much should I have expected to get in/out?

Well, that's good news.

I'd guess you just have a leaky needle valve, then. Pull that section out of your carb.. pull the needle ...make sure it has a RED ( not a black ) tip. Make sure the float looks good and not cracked or having any fluid inside it. run a q-tip inside the little tube where the needle moves around inside of.

How did it taste?

Having used to spend a lot of time under old Toyota Landcruisers rebuilding them and getting my fair share of gear oil in my mouth I can tell you first hand it's the nastiest shit on the planet.

30W non-detergent is no where close to some real nasty gear oil.

The second worst is a mouth full of carb cleaner, but mainly because it burns.

i got a mouth full of gasoline once and have had you-name-it in my eyes, but i always thought degreaser would be the absolute worst to get in the mouth or eyes.

OK - that sounds like the I don't need to worry abot the seals, and its a fuel problem.

I replaced the float and float needle about 6 months ago becasue it seemed to flood when I left the fuel tap open, even just for 15 min or so. Its possible there's something stuck in the tube so I'll open the carb up and check it. I'l also check the choke is behaving while I'm at it.

I'm also going to drain the tank and put a fresh fill of gas in it - the bike has stood outside while the engine was out for about two months through the english summer (ok not that hot but it wasn't bad) and I wonder if either some gas has evaporated screwing up the mix or there has been some gradation of the mix that means the fule at the bottom of the tank has more oil content.....

glad it's not the clutch-side seal. As long as you don't have to split the cases, it shouldn't be too hard to fix.

Check to make sure your plug isn't fouled, run a fresh tank of gas through the bike riding around town, and see how it runs after that. You may just need to blow out some debris/bad gas. May even need to degum your carb but I think that's unlikely since it had a recent clean and hasn't been sitting for years.

well with a bit of sugar and gently baked at 190 deg c the gear oil has a nice gentle crunch - would go well with with a bit of cheese.....northern england behaviour

been trying to think of whats causing my problem if its not the seal and think I might have workied it out - I suspect the whole problem related to remoing the fuel tank to change the top munt on the shock and nothing to do with removing the engine. All the shaking around of the tank will have either sitrred up all the gunk at the bottom into the fuel, or disturbed some debris thats got into the carb. Wil,l clean carb and drain tank today and then see how we go....

Just want to thank everyone for their help. In the end it was the seals - there was no other reason for the large clouds of smoke. I eventually concluded that perhaps the previous owner had sold me the scoot with not very much gear oil in and it only really became apparent when i filled it properly. Either that or they just gave up the ghost while it wasn't in use. Will never know.

In the end I got the engine rebuilt by Craig at Scooterworks here in London (I don't have access to a garage or workshop) He gave it a full work over and replaced quite a bit, including the cush which I never knew was there. Its like a new engine - so smooth - and its great to be back on it. Will post some piccies....and the big Beemer's heading for the sales!

Thanks again for all the advice

I'm glad you got it sorted. Now you can enjoy for what it was intended: Riding!

Learning as I go ...Thanks for the post..