Modern Vespa

To the NSM Modern Vespa gurus, please help a young squire. This is my first P200 and my first Vespa. For context, I rebuilt the motor with my father awhile ago, gaskets/seals/bearings/woodruff keys/shifting cross/etc is fresh, only 200ish miles on the rebuild.

My P200E isn't running right after a recent ride and my suspicion is that I ran the wrong 2T oil and caused some damage somewhere. I had an issue with the float lid on the carb leaking after running a different kind oil, but it's not the carb. I think my issue is stemming from running too lean from the different oil, potentially causing something to blow up in the cases, but I'm not an expert and some opinions would be most helpful… please read on as I will explain everything below:

On the way home from a rally three weeks ago or so, I was running low on two stroke oil after the long ride. I stopped at a local motorcycle dealer to get some oil to top off my tank a few miles from home. The only oil they had was Yamalube 2S, so I topped it off thinking some oil is better than no oil, just to make it home- I've learned now that bringing extra oil is now a must. For clarity, I normally run Motul 710.

On my last ride a few nights ago (the first since that rally), the scoot wanted to bog really hard in first and would die in neutral. Coming to a stop, it would die in neutral and Id have to bring up the throttle up much higher than usual to get going in first. I'd have to ride aggressively to keep it from bogging. This was my first inkling something was wrong. Id have to fully pin the throttle to get going in first and leave it pinned to get through second due to the bogging, but third and fourth gear were fine. This made me think, I'm getting too much fuel, something's wrong, and realized I should just go home and check things out after about five to ten minutes of riding. I went home, opened up the carb and poked around. With the fuel tap on, I noticed fuel immediately leaking heavily from the float lid. Off to the computer to order a rebuild kit from Mercato and no more riding for awhile, I thought… should just be the carb, but neigh sir.

Today I had some time to work on the scooter now that parts had arrived, so I put in a new NGK BR8ES spark plug and fully rebuilt the carb including jets, float bowl and needle with my Mercato order (original Dellorto 24/24). I put the rebuilt carb on tonight, no fuel leaks, but still having the same problems. It was hard to kickstart the scooter but I finally got it to go and it blew out a grip of white smoke when I got it to run… not good.

It wouldn't idle hardly at all, so I started turning the a/f screw until it would stay running. I adjusted the air/fuel mixture screw to the point that the slide is almost all the way open to get it to run without dying. Clearly something wasn't right, so I pulled off the carb again to check my work and it seems fine. There were no fuel leaks or issues with my rebuild AFAICT and the float lid was dry as a bone. Pulled off the autolube cover, checked the gear, everything there seems fine in there as well. There's no bubble in the line so my impression is that it's still getting oil.

With the throttle wide open it *would* run though, but would still smoke pretty bad. On a whim I threw some Motul 710 into the fuel tank and it started to run a lot better for a bit, smoked less, and it would idle again after adjusting the screw back to a regular position, but it cut out on me after a few minutes of letting it run. I decided not to tinker further and I'm terrified that I now have to pull cases because I cooked my freshly rebuilt motor due to poor decision-making with the Yamalube. Currently draining the entire oil tank to make sure there's no more Yamalube 2S and praying I didn't score my cylinder or blow a hole in the piston from running the wrong oil.

I am going to pick up where I left off this weekend and I'm calling in help from my dad who is much more experienced than I am with engines, but we're all ears in the meantime.

Am I completely off base thinking it was the different 2T oil that caused this whole fiasco? I had a great rally a few weeks ago and the scooter was running strong before all of this happened. Could the oil be the problem or is something else off? I'm confident that my motor rebuild went well as I've been on several other rides and was taking it around town before the rally without issue. The only thing giving me hope right now is that I have good compression, after doing a compression test I was right around 100-110psi.

I'm normally a lurker and don't like to post much, but I really need help. At the risk of looking silly on the internet, I beseech the gurus here for some insight. This forum has been instrumental in helping me learn about these scooters, and I normally wouldn't put myself out there like this, but I'm at my wits end. If anyone has an idea, I'd love to hear it.

- Tough Luck Vespa

Far from a guru but I'll go out on a limb and guess that the 2t oil isn't your problem. Yes, Motul great oil, but you're dealing with a more or less stock setup (right?) - in stock form these things are pretty resilient. You might get more carbon buildup over time with cheap oil but won't hurt anything.

The oil injection bypasses the bowl on the carb completely so shouldn't have any effect on fuel delivery issues you are having. If you want to confirm the injection is working you can introduce a tiny air bubble into the line and watch it move or manually push the arm that controls the oil delivery forward and see if your exhaust gets more smoky (thanks Voodoo and MJRally for those tips!)

Sounds like you have a flooding issue. Common sources could be a bad float or leaky needle valve. The carb tophat screw is easy to strip so take care when rebuilding . Also over tighting the two main carb bolts will warp the carb body and create more problems (use a torque wrench) - you can check to see if the carb is warped by putting it on a flat piece of glass.

White smoke is a concern. You're describing symptoms of a crankcase leak. Needing wide open to run and burning gear oil.
Re do the crankcase pressure test to be sure but seems likely it's leaking.

The Yamaha 2S isn't your problem (unless you added it to the gas tank by mistake).

The hard start and white smoke are classic symptoms of an oil leak. When you kick, kick, kick repeatedly you load up the cylinder with oil. The white smoke is all the excess oil burning off.

Drain your gear oil and see if it has gas in it, or smells gassy.

I'm a third vote for a bad clutch side seal (leaking between the crankcase and the gearbox).

Unfortunately, that's a case split and pulling the crank, too. Assume you'll need new gaskets to go with the new clutch side seal.

Don't worry about asking simple-seeming questions--I think you know we're more than happy to answer them and/or point to appropriate resources, so long as you listen and learn.

None of us were born knowing how to work on two stroke motors (other than Jack, whom I think was born clutching a handful of jets and needles).

Post up some pictures of what you've got and then you can watch the Hive Mind *really* go to work.

I appreciate the replies gentlemen.

I've ordered a seal & bearing kit from Scooter Mercato just in case. I have extra gaskets for the motor already laying around as well as a new Spaco I bought when I ordered the carb rebuild kit. Can never have too many parts.

I suppose my first step will be to reattach my two-stroke oil line and refill the tank with Motul. Next I'll drain the gear oil and check for gasoline as suggested. If it's clear of gas and there's no odor, I'll pull the rebuilt OG carb and throw the Spaco 24/24 on. I'm confident it's not the carb causing the issue at this point since I just rebuilt the original with a new float, needle, jets, choke, the whole 9. Perhaps a new carb will alleviate the problem, but that's hoping against hope.

If that doesn't work I guess I'll have to split the cases or keep troubleshooting at the very least. I will have access to a borescope this weekend to check things out without having to fully open the motor.

Any idea on why a crank seal would fail so soon after a full tear down engine rebuild? I'm assuming operator error, but insights and shared experience are always welcome and appreciated. Thanks again MV gurus.

Here's a picture of my Vespa from the morning of the rally. Let the flaming commence!!

No flaming. Other than the whitewalls (which just aren't my thing), I like it.

Looks coastal.
Which "way out west" is this?

Nice! I particularly like the flyscreen!

Which rally did you go to?

Very very porn star-esque! Love it!!!

No flaming from me, it's your ride, do what you want with it. It's a clean looking P - better looking than anything I ever owned, for sure.

More bad news. I drained the gear oil and replaced it, hooked up the two stroke oil line, filled it back up and started the bike. Picture is of the bike running about 3/4, billowing more white smoke than the Vatican when they select a new Pope.

I just noticed that my muffler was loose while running it, imagine my shock... I have no idea how long it was like this, but the pipe was bouncing where it meets the motor. I fear there's a chance I let entirely too much air into the cylinder ans a result of it being loose, causing the motor to overheat. I'd bet that I fried the seals, or possibly cracked the piston rings, or worse at this point. I'm afraid the only way to assess the damage is to pull the cases and rebuild the motor. A costly rookie mistake… I think that would explain the compression being somewhat low at 100ish PSI and the scooter only being able to run at full throttle.

We put a borescope into the cylinder and the top of the piston is caked. There's also some scoring in the cylinder wall. I'll post some pictures of that shortly. More bad signs.

I'm thinking at the very least a new muffler, I'm thinking Malossi Power Classic. This one is an old Sito Plus that was sitting in a field with the scooter for years before we tore the bike down. I'm also thinking a new cylinder kit, and a full rebuild kit for gaskets and seals, cush drive, etc. This could be a $500 mistake so please friends, don't be like me.

Any other input would be appreciated. More pictures soon.

Borescope picture, as promised. My theory right now is that it's way too hot in the cylinder due to the loose muffler/blown seal to the point that it's baking the oil onto the piston, further worsening the lubrication situation. I learned in shop class many years ago that the #1 cause of engine failure is overheating…

If anyone has a better idea, please tell me. I'm crestfallen.

The clutch side seal (definitely looking like your issue) can be tested in place.
Start by removing the clutch breather, get the motor running and put your finger over the hole. If there's pressure there then your seal is leaking.

It's easy to think the worst when you don't have much experience to go on. Assuming it's running way too hot, without a temperature figure, doesn't help. Get yourself a TTO cylinder head temp gauge and you'll know for sure.
A blown seal or loose exhaust won't have a drastic effect on temps in my experience. Running way too hot will give you a very light-coloured piston and plug.

I doubt that high cylinder temps would affect the crank seals.The case is a pretty big heat sink and the crank is constantly bathed by fresh, cool fuel. Extreme heat would also seize the piston.

Heat didn't effect the seals. They'll last long past the point that the top end seizes up.

Nice rally! Both of my hobbies in one.

Did the clutch breather test. Removed the clutch breather and put a finger over the hole. When kicking the scooter over, the clutch breather port wants to blow air out, you can feel it. When the scooter starts is running, the port wants to suck air in.

We added some glass cleaner to watch for air leaks to confirm our findings after this test, and it wanted to suck the glass cleaner in while running.

What does everyone think?

https://youtube.com/shorts/em7920f4Rrs?si=9sw4hhrEY-HEMCzf

Uploaded a YouTube video of the phenomenon.

Going to try to swap carbs with my new Spaco but I'm preparing myself to pull cases.

Pulling in the glass cleaner, is pretty much the same a pulling in the oil from the same compartment. Which suggests an air leak.

I think your clutch side seal is toast and you're going to need to split the cases and pull the crank to replace the seal.

I appreciate all the replies and insights, thank you all. I'll post again when the engine is open.

Incorrect seal, like a metal seal when there is a groove for a rubber seal. Less contact surface and it slips out.

Rubber seal with no groove for it to expand into to hold it, especially if installed with grease.

Installed too deep. Rides against the inner race of the bearing and melts.

You were correct, my crank seal failed. You could actually see it rotate with the crank while the motor was on the stand. It was a blue crank seal that was incorrect for the application. I should've taken a video.

Attached is a picture of the cylinder. It's not as bad as I thought it was, but I went and got a new stock cylinder anyway. The crud on the piston tells me it was running a little rich. The cylinder looks glazed to me, but there's no major scoring.

Hopefully all the parts will be here by tomorrow so I can replace the seals and gaskets, install the new cylinder & piston (chamfering ports, setting ring gap, etc), and button it all back up. While everything is open we're also going replace the kickstart quadrant, rebuild the clutch, replace the neutral switch and install a new Malossi box exhaust.

I've never chamfered a cylinder before, much less ported one, so I'm a tad hesitant… but I think it will be worth it to have a fresh new cylinder while the cases are split. Should run like a top.

Again, thank you all for your insights. Perhaps I will start a build thread.

That cylinder looks pretty good to me! I don't think you effed anything up to bad. If you soft-seized it would be all scuffed up. And even then you could ride with it unless it was really bad.

Ah such an innocent and dangerous statement, before too long you will be like some more of us on here... more scooters and parts than you have space for and a reluctance to part with any

So the chronicles continue…

Today was the first start-up after replacing the crank seal and putting the motor back together with fresh gaskets, rebuilt clutch (new plates, springs, etc), new stock top end (cylinder jug and piston) and a new muffler.

https://youtube.com/shorts/AnNCF4qKOrQ?feature=share

This is a video of it running on its first start-up. There's this whirring sound and I'm unsure what it could be. It sounds like it's coming from the carb. Any insight would be helpful.

Are you installing the clutch side seal in the correct orientation?? To me it sounds like the seal is rubbing on the crank…

I'm not even sure it is possible to mount it the other way round, would the case close ?

Spiritof1993 did you check the clearance between the seal and the bearing ?

The only one I have ever seen been installed the wrong way round was tje full rubber seal. That one is possible.. I've never seen the metal shield installed tbe wrong way round

Maybe he installed the rubber one the wrong way ?

This noise is really strange ! Never heard something like this before

Pic is only for reference, the rubber seal can be mounted the other way around but I've also seen the same with the metal one. How they managed to do it though, I don't know…

They probably used a hammer to close the engine

It sounds like it's coming from the carb/air box to my ears. Do you have the fiber/spacer washer mounted underneath the airbox?

Pull the carb and airbox. Make sure all is kosher and then torque the carb back into spec.