Modern Vespa

Hello

Took the P200E out today and I noticed once I get to a certain RPM, it would falter or stutter.. As if it was governed by something.. Seems to happen no matter the gear.. It would also almost backfire.. I could hear something being blown out the exhaust.

I recorded a video: https://youtube.com/shorts/uQj1BoiFu3U?feature=share I have it almost full throttle here.

When riding, I would give it near full gas and it would lurch forward then stutter/falter then lurch.. I'd up a gear and it was better until it reached about the same RPM and same thing..

It did not do this at the start of the ride, only after about 1hr or so.. I'll wait for it to cool down and try again and see if it isn't heat related.


Any ideas ?

cdi ?

Clean out jets, filter and carb. Get a new plug, cap and wire. What plug are you running?? Grab a new CDi. They're not too expensive.

Hi

Some more updates.

This Vepsa was completely restored from scratch.. All plugs, wires, electronics are new. It has less then 100 miles on it.

I let it cool for about an hour, got on it, and let it rip. No issues at all ! I think maybe it's the plug..


I took the plug out and it looks like this..

Looks like it's been running pretty rich for 100 miles, I'd say.

Yeah your plug shouldn't look like that after just 100 miles...

Which could mean the plug isn't new but more likely you've got a different issue. You're not premixing 2t oil at 2% AND running autolube are you?

For the first tank of gas, we used the autolube and added some more 2T oil. But after that, it was just straight gas.

The plug is new.

Is there any relationship between how this plug looks and the symptoms I was seeing ? That is, after running for an hour or so, it starts to stutter, surge and slightly backfire ? Then when the engine is off for an hour, all those symptoms go away ?

My money is on the cdi theory, then, since it's heat/run-time related. I've had several cdis over the years that acted up when "hot". One new one failed/ was bad. Is yours a true Ducati cdi or a knockoff? If you can, try a new genuine Ducati and see if the one you got is bad.

Plugs are a consumable item and need replacement regularly. Looks like its running rich all over and maybe too much oil. Get a new plug for sure. Most likely the reason its running like dirt.

Sounds ignition related, so either CDI or Pick-up is my guess....

Thanks everyone for the replies. I really appreciate it.

I've ordered new plugs and leaned out the carb a little (so much better off the line now) and I ordered a new Piaggo CDI https://www.sip-scootershop.com/en/product/electronic-unit-piaggio_85000000 from SIP.

Also, could it be the flywheel ? I think I remember reading that magnets lose their magnetism when they get hot..

I had a chat with the mechanic who restored my P200E. He has to see it to understand what it's doing.

But, he did say the CDI is a Ducati and is new. The flywheel is also new.

I'll pop in a new plug tomorrow and lean it out a little more. I tried to reproduce the issue today but the closest I could get is, in 2nd gear, at the higher end of the RPM range, it would stutter and falter.. But in 1st, I couldn't quite reproduce this... Wasn't on a stretch of road that would permit me to test in 3rd.

It almost feels as if it has a rev limiter in 2nd..

Looks like gear oil.

Any chance of a bit more history on this, when you bought it etc.

You say it was restored less than a hundred miles ago so are you seeing teething issues with the work done, and do you need to take it back to whoever did the work and get them to sort it.

The more you change stuff trying to diagnose, the more this becomes your problem.

Which plug are you running? Just throwing another question at you.

Found this LINK on the forum. Different choices for different riding.

+1
And the more you ride it while high rpm backfiring, with what could be a seal leak, the more damage will be done.

1) what jets are you running
2) what are you doing to lean it out?

If it's the mixture screw, that won't fix your problem. It really has an almost unmeasurable effect past 1/4 throttle. And leaning it out from stock (1.5-2.5 turns out) is just asking to seize when closing the throttle after you top a hill.

If it's the main jet, also stop leaning it out. Unless you are larger than stock, there is no reason you should be leaning it out.

It doesn't appear to be running rich to me. That plug is almost surely just fouled from oil. It has only been run 100 miles. Chances are it looks that way because you had too much premix with the autolube still active. No biggie. Imo the plug color is probably a red herring in your case. Put the jetting stock and just replace the plug (don't forget to gap it).

Then re-test with the clean plug. If you still have the problem, THEN swap the CDI and try again. Change only one variable at a time

I put in a NGK-BR6ES (4922) and tested it out for 30 minutes or so.. No issues.

But, truth is, this issue doesn't always happen. I haven't been able to figure out how to reproduce it.. I'll go for a 1hr ride, no problem.. Take it out for 30 minutes, it will sputter, bog for a little bit then be OK again..

I spoke with the mechanic, he says to bring it in.. But if I can't always reproduce it, might be wasting my time.

Let's see how it goes with the new plug. If it does it again, I'll bring it in.

The carb is stock as are the jets for a 1982 P200E

Thanks everyone for the responses.

I recently had to replace my sparkplug wire and cap. It turns out that the wire was strecching too much from riding two people. The combination of a softer/older suspension was making the wire to stretch just enough to cut power by slightly separating the cap from the sparkplug.

I changed the wire and put a longer wire and replaced the cap with one that allows the sparkplug to retain the screwy little aluminum cylinder at the top. Now the engine runs more solid compared to before because I was getting intermitten spark.

with black plugs dont forget about the weak spot of all vespa lf engines: the gearbox oil sucking
many engines suffer from that

Had this happen with a BGM siliconized case gasket on an older PX. Maybe made a mistake by greasing it, but it looks like there's too little meat at the weak spot to get a solid seal with that silicone bead.

Ran ok a few days, then like crap. Plug looked like that pic. Cylinder had gear oil in it. Doesn't take much to foul a plug.

Opened it up and found a little oil trail there.

Probably too early to say for sure. I'll report back if things change. But, have ridden for another 3-4hrs total on the new plug and no issues. I will return the air/fuel mixture screw back to where it was as it does seem to take a little longer to return to idle..

I am waiting on some rivets from SIP. The rubber trim around the side panels is SUCH A PITA to keep on. I used a little bit of grease which helps.. But without the rivets holding the ends in place, it's a constant game of whack-a-mole trying to get those side panels back on without losing the rubber trim.

Funny, totally different beast, but I have a similar problem with my 4T Stella.

It's been running fine, but this past weekend my wife and I were out riding. Cruising along at about 55 all of a sudden I started losing power. It just quit. I cruised to a stop in a parking lot and it started right back up.

I can ride hundreds of miles with no issues and then just once in a while it will quit. Never leaves me stranded, but it's annoying.

I haven't nailed it down yet, but it's a Stella, so I might never.

I've seen this before with other motorcycles. Generally speaking, its a grounded wire- I would check the kill switch first.

Hello

I am fairly certain the issue fouled plugs..

This is the 3rd plug I have gone through since I got the bike in May. I have done about 400km's so far..

It started to stutter/faulter again today. It only seems to do this when I am half way or more on the throttle. If I putter along, no issues.

Anyhow, pulled out the plug. This plug has maybe 200km's on it. I know that if I change plugs, it runs great for a while.

The mechanic who rebuilt this, had added 2 stroke oil to the first tank plus whatever the pump puts in. That's definitely cleared out. He also obviously greased all bearing etc. So maybe that is still burning off.

Now, with that said, this plug is the least fouled looking of the three.. So maybe things are starting to finally clear out.

The only other thing I can think of is gear oil is leaking in.. Any way to test for this ?

What say you ?

I had the exact same symptoms and it turned out to be incorrectly set timing. Eventually, it wouldn't start and would foul the plug and spit back fuel if I kept kicking it.

Even after figuring that out, it was hard to start sometimes until I took it for a couple rides and got it good and hot.

I have replaced the CDI.. Let's see if that does the trick.

When you have the stutter, try to gap the plug to 0,5mm.

I also had the ignition timing too retarded and all kind of weird behaviour with a new plug. It helped when I gapped the plug to 0,5mm but really cleared up by adding ignition advance to the spec.

My two pennies worth. Sure it's not something as simple as a float needle? Too much fuel and flooding when your throttle opened up? Check the float / needle ? Blacked plug to me is either ignition issue or carb issue. Backfire in exhaust, normally timing but can be rich mixture, if floats not closing off you are flooding engine and it's going boom. Had all this nonsense a week ago with mine, new cdi didn't sort but the spring loaded float needle had sticky plunger at floats end. Soaked it with carb cleaner and blew out. All my hot starting and running issues including small back fire spits have gone away . Put in new plug too as once fouled that bad I throw away.

At least now I have a good idea what is causing the stuttering / faltering: fouled plugs.

I will take it back to the mechanic who sold it to me and ask him why I am fouling so many plugs. I'll suggest timing and maybe carb float needle.

It's got a 1yr warranty.

I wasn't crazy about going before as it was hard to reproduce the issue.. But now I am certain the issue is fouled plugs. He just has to figure out why.

I'll report back when I get some news.

Thanks again everyone!

Why haven't you taken it back sooner, you've said in a different thread that it won't pull 4th gear so there is obviously something amiss.

A warranty should give you the assurance that you can take it back and get it fixed.

Simply because it was very difficult to reproduce. He would have had to ride it for over an hour and only maybe would have the issue come about. I wanted to be able to point to something specific ie "fix this" before going in. Otherwise, it would have been a game of "works great for me"..

But now that I can say "three plugs in < 500km, there's an issue here", it's a lot easier for him to diagnose.

Hi everyone

Finally brought it in to the mechanic.

My P200E is a 1982 model for the Canadian market, but for some reason has a 20/20 Carb. He leaned out the main jet, took it for a good spin and it seems much better.

Let's see if I foul another plug. He did suggest that this winter we install a 24/24.. But on the ride home, she sang great.

Now, I do have one other issue that we didn't fix which is that my idle screw is nearly bottomed out and while it idles fine, my understanding is it should be idling a lot faster.

One thing I did read from: https://modernvespa.com/forum/post881990#881990 is that maybe it's getting it's idle from the main jet ?

The later P200's in the US market (and likely Canada) used 20.20 carbs. My P200 came with it. Honestly, there is no discernible performance difference I can tell, as I ran it both ways.

Right thanks.

I was going from this: http://vespamaintenance.com/specs.html where it states that "older models".. maybe he meant "later models" ?

older is relative. for us in the US, there were only a few years of P series before Piaggio gave up on the US market. But the rest of the world kept getting PX bikes for decades. Thus our "late" is still early for the P overall.