Modern Vespa

Greetings from a new member and a new Cosa 2 owner from Greece. I apologise in advance for my first post being technical but I am heading to a mechanic tomorrow and I would like to know your opinion and advice.
I bought a Cosa 2 200cc a month ago to move around in town (approximately 5-10 km a day). Yesterday morning we were heading with the wife to the market and the engine seized, rear wheel blocked, kickstart became rock solid. That happened 1km after we left home, in full traffic and on first gear as I started from traffic light. As soon as the engine was cold I set the piston free by putting a gear and moving the bike back and forth a bit. After that engine was running good like before. Kickstart compression, engine noise , power all seem normal.
The scooter model is Cosa 2 1994 200cc without ebc, and it has a cast iron cylinder (I am not sure if all the Cosa 2 should have an aluminium cylinder. If so, maybe the cylinder was replaced at the past).
- Scooter was running auto lube which seemed to work because I was filling the tank normally all this time. (Motul 2t scooter expert oil)
- A small leak was present somewhere under the airbox which I was planning to take care soon, but didn't seem major (quantity of a few drops a week)
- I changed the gear oil last week and didn't seem to smell or look like it had gas in it (but I am not an expert so not sure if that would be really obvious)
- Took the plug off to see the condition BUT unfortunately I did it after I returned home (that 1km) and after I put about 1% of oil in the tank as a precaution in case the autolube didn't function good. I also chopped it to take a look deeper. Plug is ngk B8es

Unfortunately I don't have tools space or friends here to help me so I will go to a mechanic tomorrow to see it, but any suggestion and opinion here will be considered great help and highly appreciated.
PS: I sincerely apologise for the long post and thank you if you took the time to read it

Hi there!

Don't have any experience with cosa bikes but have seen a few in my area.

Sounds like it could be a jetting/not enough fuel related heat seize, especially if the oil pump is still working. You can double check the pump is working if you have a clear hose, by pinching the oil line with creating a small air bubble and seeing if it moves along as you rev the bike on the stand.

Also check the cylinder base for oil and if the exhaust has oil coming out… this will make your bike run lean.

It's best if you could check the carb to see if you're using stock jetting etc… at least you'll know what state the carb is in.

But no tools or space, I'd look for a trusted mechanic (someone you can trust, not someone who has been in business for 30 years) who has worked on vintage Vespas before.

If not, you could be going in circles for a long time.

Thanks 108, I am planning to ask him to check the carburator tomorrow anyway. The jetting is not stock for sure, previous owner told me that it was upjetted at the past and also gave me the stock "needles" and jets. He also told me the engine was the original stock and the exhaust too, and I didn't ask much to be honest as the bike was running exceptionally good at every gear. I don't have access to the scooter today because I m off the city but from a video I made a screenshot the exhaust connection looks like this

Exhaust doesn't look too bad, but that points to other problems.

Especially when you mention you've up jetted (I assume you don't have any upgraded parts) from stock. So the previous owner was trying to compensate for lean conditions. There's no real reason to up jet. Which suggests there's deeper gremlins inside.

Guessing crankcase seal leaks then.

I guess the mechanic will check for air leaks in the engine anyway. To be honest I made the conclusion that the carb it's up jetted because guy that I bought from told me that his mechanic tuned the carb, it's consuming a bit more, and if I want I can install the stock parts to be more economic in consumption. So I got the impression it was maybe tuned to perform a bit better, maybe because of age, old exhaust etc. And since he mentioned bigger consumption I thought of a bigger jet. I will post the numbers when carb will be cleaned. What I have (considering) stock now is a be3 mixer, 160 main jet air correction, 48/140 idle jet and a bunch of main jets including 92,96,98,102 and 116. So whatever is in the carb I guess it's not one of these. I really hope it's tuned on the lean side, and I say hope because that way I guess the problem will be fixed relatively easy. What troubles me is that the plug is completely black…

So I visited the mechanic today and he said that most possible cause of siege came from lack of oil. He said that in such a short distance and going so easy on the engine its impossible to siege due to lean mixture (meaning from a small air leak or wrong jetting). He told me to top up the oil tank, premix the gas a bit for safety and make a couple of short rides to make sure the autolube is still in function and take it from there.
In the meantime I came across this older post form Magg
https://modernvespa.com/forum/post1660351#1660351
that states there is a check valve that if fails could be the problem if the oil level drops below the pump.
That can offer a suitable explanation as I left on purpose the oil level to drop more than usual this time to check if the warning light works (still has enough oil in the tank but much lower than usual).
Does a Cosa have a sensor/check valve like that?

I think that only Cosa II has the oil indicator sensor, my Cosa I just has a dip stick in the tank. I think all Vespa autolubes have a check valve, but that's a separate thing. Your plug looks like possibly too much oil, but maybe just because you added oil to your gas.

Is your oil feed tube to the carb clear? You can usually introduce a small air bubble by disconnecting for a second, then as mentioned watch to see if it moves w/ motor running, but your clues indicate that it works. I agree w/ your mechanic to make sure it's working & run premix meantime - your bike should be a lot smokier if the autolube works.

Regarding jetting, I know these are different than other 200cc Vespas because they have more air filtration and thus more intake resistance. You should have a special airbox snorkel that leads to a second large filter under your seat. You need to jet it to Cosa specs if you have all that, or likely P200 specs if it was deleted.

If your motor is Cosa II, I believe it probably came w/ aluminum cylinder originally and is still single rigid wire shift. I have one of these motors in Pireaus. Is yours single wire shift?

[quote="V oodoo"]
Hey Voodoo, yes it has the single solid wire shifter cable, and it has a plastic airbox in the frame around the tank area that accepts a square foam filter (I changed that one last week).
Mechanic told me that same thing about the smoke, I will check it tomorrow and let you know.

Regarding jetting, I was checking today the jets I have (which were replaced and they supposed to be the stock ones), and they are the jets, mixers etc that the COSA 1 workshop manual has them as stock (92 main jet, 160 air gauger, BE3 mixer)

COSA 2 manual mentions BE6 mixer, 96 main jet, 140 air gauger, and the rest are the same
It will be interesting when I will clean the carb to see if the above are now installed, but then I will be troubled on why there were not there from the beginning.

PS: when will you be on Piraeus to bring you the scooter for treatment?

Hello from Ireland
I have a Cosa 200 and it also seized shortly after I bought it. The cause was a damaged auto lube cog. This damage was possibly caused by the cylinder dowels being put in the wrong way around: they are threaded at both ends and the short thread end should be installed into the crankcase, with the other end for the cylinder head. If the long end thread is threaded into the crankcase one of the dowels can rub against the autolube cog and damage it.
I found the best way to check if the autolube is working is to fill the oil tank completely and then run the scooter (at moderate speeds) on a petrol oil mix for 20/50 Km. If the autolube is working, the oil level will have dropped visibly
Hope this helps
Cosanigel

Hey Nigel, that's a pretty Cosa you got there!
I am leaning towards autolube function myself given every other parameter.
It is mentioned in another thread that an engine sieged when the oil tank level was a bit lower than usual, and it caught my eye because when my engine seized my tank was a bit lower than usual too (I wanted to check if the warning light works).
So I found this amazing video on YouTube that they explain some autolube problems and they mention the possibility of loose autolube bolts torque, which sometimes when the oil tank is lower than usual can lead to a reverse oil pump which can leave you dry for a bit.
Another reason described in the video is that it seems that after 1990, the autolube cog's surface were prone to natural damage over time from the "nipple" that is driving them. When the damage is significant, the cog can't open the oil passage enough and you run dry. That happens usually on low throttle and speed because the cog damage is most of the times bigger there (considering that a scooter is usually moving small distances at low speed).
In the mean time I am waiting for an autolube gasket to arrive so I can find time to take and clean the carb and also open the autolube to check if any of the above is happening. I will post back when I do so.
I am also running premix all this time and the oil tank is getting lower which means the pump is feeding oil. What I am not sure though, is if that amount of oil is enough, which it won't be in the case of a worn cog.

Here is the video, it is Italian but you can put CC auto translate in English
The part about problems are around ninth minute I think. I will post it on the relative threads too

Update after a month
I took the time yesterday and took everything apart, including the oil pump ofcourse.
1. 1st thing I noticed was metal shards on the shaft drive. I can't figure where they came from, everything in the airbox were clean
2. If the siege was caused by lack of lubrication, that seems to be the "nipple" that drives the pump. It looks maximum worn and I have to replace it if I find the cap. The pump gear is good

Edit: I m thinking about the possibility those metal shards on the shaft, to come from the "nipple". They stick to a magnet so they are not aluminium

Can I just tap the oil line, leave everything in place and run premix temporarily till I find the part? All this time I was running the scooter with 1% premix for safety, and the pump working (oil was going down in the tank but I am not sure if it was ending up where it is supposed to. Some of it was leaking out of the carb box for sure). Considering that I was moving small distances around in town, I think 1% would be sufficient even if the oil didn't end up in the carb like it should