Modern Vespa

I've been working on replacing the cylinder head gasket on my 2018 GTS 300. I removed the old gasket today. As a complete novice, I have all sorts of questions…

1. How "smooth" should the surfaces on the various top end parts be on a scooter with 2500 miles? Should they be totally smooth? Like a beer can? Mine are not… They are coarse in some places. The scooter has never been run low on oil or over heated. Do those parts just have a bit of galling as part of normal operating?

2. Oddly, I didn't see anything wrong, specifically, with the old head gasket. There is rust around it for some reason. See pics (sorry about the weird pic orientation). Thoughts? Should the rust be removed before I fit the new gasket? If so, how does one remove rust? How should I clean up these surfaces/parts anyway? Parts cleaner? Brake cleaner?

3. The base gasket has some rust around the exterior of the gasket, too. See pics… I was hoping to leave the base gasket undisturbed, as I'm already in over my head, and piston rings sound scary… With the rust and all, is leaving the base gasket in there a bad idea?

Thanks again…

1) they should be clean/shiny. They don't have to be perfect, you just need a clean, flat and reasonably smooth surface that is devoid of old gasket material, carbon or oil.

2) don't freak out about the rust on the edges. If desired you can knock it down with a scotchbrite pad or 400 grit sandpaper. Follow up with brake cleaner and a LINT FREE rag.

3) the rust doesn't matter with respect to the base gasket and you'll get differing opinions, but I am in the camp that believes you should replace it because you have removed the clamping load and effectively disturbed the original seal. If you are careful you do not have to disturb the rings and can remove the piston and cylinder as an assembly. You want to gently rotate the crank and lift the cylinder up from the engine case until you just barely expose the piston pin. Then you can remove one clip and the pin, and remove the cylinder and piston together. See my attached photo from my BV350 top end rebuild.

Good luck and don't worry, you're doing fine!

Yes, yes and more yes. Yes times yes squared to the power of yes. Unless you want it to be the next reason your top end fails. It's a cheap piece of paper with some stuff on it. One reason there seem to be more failures on the 300 than the previous bikes is that Piaggio took out as much metal as they thought they safely could when they enlarged the bore. Maybe they got carried away, who knows. There's not a lot there anymore to put a gasket on and seal.

Thanks again everyone. I'm going to attempt to remove the piston and rings together, though I'm not too sure of the process. Engines are well understood by most of you, but to me, they operate using magic spells. I view this whole experience as learning to cast another Vespa magic spell…The mechanical and physical aspects are all lost on me. I understand that some sort of gasoline vapor explosion takes place in the engine, but where that occurs, and what happens, and how the engine harnesses that power… IDK… Magic. Anyway, thanks again and another question…. Do I need to "clean up" the front of the piston if I'm removing the piston and rings together? How would I do so? Why's it so dirty?

No answers from me, but I am watching this with complete interest. I'm just about to get started on mine. I wish I could find a step by step of all and only the head gasket change. I've been putting it off, but I just need to twist up my courage and get started.

Seconding his question, what do you use to clean everything up? Simple green? Brake cleaner?

There is no magic. Google "how a
4 stroke engine works" and watch a couple of videos.

The "dirty" you refer to is carbon. It is a by-product of burning fossil fuels. If you aren't removing the piston from the cylinder, don't worry about cleaning it.

I Googled "how a 4 stroke engine works", and all the results were "magic"… You must be Dr. Strange or Houdini if you understand all this…

Jk… Actually, I understand it a little more now that I've taken the engine apart. The explosion occurs somewhere, it must push that piston down which turns that thing it's attached to, which must be connected to stuff that makes the wheel turn… like I said, magic.

You're braver than I am Kim. So far, my GTS doesn't need that sort of engine work. And even though I have rebuilt a number of VW, Corvair, and Ford engines back in the early 1970s, the thought of replacing a head gasket or rebuilding the GTS engine is something I have squarely put into the "time for a new scooter" realm.

A trip to a NAPA dealer with an inquiry like "what do you have that I can use to clean the carbon deposits off my piston" should provide some avenues to explore!

Good luck with your wrenching adventures.

If you really want to clean the piston get a can of carb cleaner and a scotchbrite pad.

Vespafsw3 - if you've rebuilt ford engines a head gasket replacement on a Vespa is a walk in the park. With a little of determination and the proper tools you could start the job when you got up and have it running around lunch time.

Don't be intimidated by this. I just completed an entire top end rebuild on my 2013 GTV 300. If you have not done so already, you should watch the vespa Malossi Cylider kit installation from Robot at Scooterwest. Be prepared when moving the Barrel with the Piston, it will stick really hard, because of the Small "O" rings on the studs. These studs are supposed to be one time use, but I have heard people using them again.

To do the base gasket you will need to purchase the 4 "O" rings. I am not sure if they are a special heat treated rubber, but they should come with the rebuild kit.

Take your time and make notes. I took lots of photos, and it came out nice. Except I was horrible at adjusting the valves. Make sure to tighten and not over tighten them.

The other thing is check and recheck TDC. when tightening things parts move. Its annoying .. When you are done you will be proud of yourself.


Resetting the Rings on the Barrel. Take your time and remember the Rings need to be staggered. GTS300 Compression problem, White smoke, Engine sputtering Here is a post which shows it.

If you have a plastic pry tool used on Laptops or PC's. I would recommend using it or very carefully with a blunt flat head screwdriver to gently push the rings in the groove as you are sliding the Barrel on. Don't rush this step and add a little oil to the sides of the wall. to give you some lubrication.

You keep saying that. Seems like you are getting in your own way. Stop and consider it for a minute. That explosion is gasoline vapor ignited by the spark plug. Where does the gasoline vapor enter the cylinder? Where does the plug spark? That is where the explosion is. When does it happen? When the piston is at the top of its compression stroke so that the explosion forces the piston downward. Like all other mechanical devices, a gasoline engine is basically logical in how it works.

What he said. You've already got things apart. Spend a few more dollars and do the rebuild right. Replace the base gasket. Clean up the piston. Replace the o-rings.

For me, the hardest thing was getting the barrel back over the piston. The rings are quite sharp and fiddly. I ended up breaking a ring trying to reassemble things without a ring compressor. Mechanically educational. Never thought about popping the piston pin out. Would have saved me some grief.

Yep, works great. Even if you have already removed the cylinder from the engine and left the piston attached, depending on the ring compressor used it can sometimes be easier to pull the piston pin, put the piston in the cylinder on a bench, then install the assembly to the rod and case together.

I used 409, followed by 91% alcohol, followed by acetone. It will dry almost immediately. I use lots of nitrile gloves. At this stage, cleanliness counts.

And to the OP: You can get the piston/rings out with the cylinder if you are very careful. At somepoint in this process, you will PROBABLY slip and the rings will slip out. Dont worry... they are not difficult to get back into the cyclinder. Make sure you put a paper towel or something in front of the hole in the engine when you try to remove the wrist pin... you don't want it flying into the engine.

Having done it a couple of times now....
Even if the ring compressor is your fingers, it is easier to go ahead and insert the piston/rings into the cylinder THEN slide the whole thing on (base gasket first!) and attach the wrist pin/retainer ring. Remember to put a power towel in the engine opening to prevent the retainer ring from dropping into the engine, and remember to REMOVE the paper towel before closing the whole thing up! Use rubber gloves and keep everything clean and dry and oil/contaminant free (remember to lightly oil the cylinder so that it is not dry at first startup!).

rdhood - Were the engines you did this on done optionally (e.g. adding a big bore) or, like mine, out of necessity. I've grown weary of Vespa repairs… The ECU/throttle body and water pump needed replacement in my 2015 GTS300 by 15,000 miles and now gaskets are needed in the 2018 GTS300 with 2500 miles? Ridiculous, IMO.

My 2006 Toyota Sienna has 170,000 miles on it…. It has needed regular maintenance and wear items - oil, brakes, tires, timing belt and then shocks/wheel bearings at 165,000 miles. The one major unexpected repair was a coolant leak from the knockout panel at 150,000 miles… That's it.

Who makes the "Toyota of Scooters"?

Thank you everyone for the advice… I may tackle this tomorrow since it's gonna rain, and I need to mow the lawn now before the rain. I'll report back.

Honda and Yamaha.

You have the Fiat of scooters.

You left out Suzuki....

Lol. There was an old saying here in the States that Fiat was an acronym for "Fix It Again Tony".

Not sure, but I have a good idea who makes the "Honda of Scooters"

Yamaha has done a lot of work for Toyota, and Porsche, and Ford, and... etc, and Suzuki also makes some very good scooters. Yamaha tend to be a little more modern, mechanically speaking, and Suzuki is somewhere between the two.

I agree it's ridiculous. Thankfully there are many, many reliable examples out there. That doesn't help your situation unfortunately, so I'll tell you once you've done a head gasket on one of these things you'll find the following:

1) it's not that difficult - a little more complex than your lawnmower, but not much.

2) you can do just about anything to one of these scooters in your own garage. It's always good to know how to work on your bike, no matter who manufactured it.

I did it a couple of times because the FIRST time I assembled everything, one of the re-used engine bolts holding it all together twisted and snapped while I was torqueing it all down. I had to get 4 new bolts, new base/head gasket and grommets, and do it again..

By the second time around, I had the "install cylinder & piston together" down pat.


BTW, I did a complete top end... cylinder/piston/rings, purchased a used (10k miles) head, also replaced cam shaft and exhaust port valve rocker. I did a waterpump, too, while the engine was out. The original description was "one could smell coolant in the exhaust". Since the bike had 20,000 miles, I decided to just rebuild the top end and waterpump. While it all sounds really complex, this was for a cosmetically okay 2016 GTS that was $1400 so I have a good bit of financial room to work with to make this run.


I assembled it all last weekend and started the engine. It started up and idled the first time!

As an American who has owned several MGs and Triumphs (incredibly unreliable), a Renault Le Car(incredibly weird), Chevy Vega and Corvair, and almost every domestically available brand of car, motorcycle, and scooter since 1972, I can say that owning a fiddly vehicle is something I do because I WANT to interact with its mechanicals. Re-timing an MGB with a continuity light during a rainstorm, or freeing its stuck starter shaft on a hot engine during a date night, or figuring out what the French designers were thinking when they put the radio in sideways and decided 3 lug nuts was okay, is character building. The Vespa's front suspension? Historically interesting, but terrible. Character building.
Japanese (and more recently, Taiwanese) scooters are basically refrigerators-they run reliably in the background with little owner input for years. Ignore them, they run. Abuse them, they run. They have their own style, but mostly are for people who need dead reliable transportation and lots of storage. I've owned a Silverwing, big Burgman, Helix, and several Majesties, and they were basically bulletproof, but I keep coming back to Italian products for their style and quirkiness, and because they force me to stay involved to keep them alive. Weird, I know.

Purposely. We only get the Burgman here and it generally is competing in a different market.

Oops, I wasn't trying to besmirch Vespa like that, lol. I just didn't want to say it was the Ferrari of scooters, cause that's definitely not right!

Being that I have owned an 81 Fiat spider electronic fuel injection, and a bevy of Alfa Romeos in my 52 years. I would consider the Vespa the Alfa Romeo of scooters. It is beautiful and with little effort will get you from Point A to Point B with unique flair.

I am Italian, so I am a little biast, but the looks you get on a Vespa, are the exact Looks I get while driving my 73 Spider through town. It brings people back in time to when they were young and grounded, to a 5 speed manual transmission.

OK enough Nostalgia for now. MG, Vespa, Fiat, Alfa, Lambretta,Lancia for all their mechanical quirks stand out in a crowd of Brands.

Thanks again for all the feedback. Frankly, I love the Vespa's style and the riding experience. I'm big at 6'2" and 220 lbs, and it fits me quite well. It looks amazing and is available in a rainbow of colors. It's fast (compared to my Yamaha Vino 125, at least) and can keep up with highway traffic. The ABS and ASR make it relatively safe. And my hero, Justin Bieber, loves them too. Okay - maybe not the last one…

But, honestly, I like to ride my Vespa, and I'm having to wrench out of necessity. When Justin Bieber's Vespa needs a head gasket, do the Vespa dealers tell him, "Um, yeah, maybe we can get to it after riding season," or "We aren't too familiar with doing a head gasket." ?

I can dig it.

Oh yeah - more questions:

1. If I'm going to (hopefully) leave the piston in the cylinder, can/should I clean the piston face while it's in the cylinder before removing the entire unit? Or will carbon, scouring pad remnants, and brake/parts cleaner somehow leak behind it and muck things up?

2. See pic below - sorry about the orientation - I have to hurry off to work and can't play around with the pic to rotate it. Is a piston face typically this dirty after 2500 miles - i.e. Is this "level" of dirty piston at 2500 miles an indicator of something wrong or just normal accumulation?

Looks very normal to me. Keep the piston at TDC, and add a smear of grease around the edge to stop dirt getting into the gap. Then scrape with a copper 'knife'. A bit of 3/8 copper tube hammered flat will do - just sharpen one end with a file and scrape away. Clean up with brake cleaner.

You also want to cover the oil and water tunnels. Don't let any of the dirt or debris fall in to them.

You do not have to clean it. It will look that way again in short order. But if you really want to, as others have said - piston at TDC, before you remove the cylinder. Grease around the gap between the piston and cylinder wall to keep any abrasives out of the ring area. I would use a scotchbrite pad and carb cleaner rather than a copper knife. When you are done, and after you have removed the piston and cylinder as an assembly, you can gently push up on the piston to push out the grease and expose the sides above the first ring land. Spray it liberally with carb cleaner, dry with compressed air (if you have it) and re-oil with motor oil. Push the piston down into the reinstallation position at the bottom of the bore and continue your work.

Removing the base cylinder with the piston remaining in it was unsuccessful. Can I just leave the piston in its present location (see pic), replace the one pin clip I removed, and somehow fit the base cylinder over the piston once the base gasket is in place? Or do the piston pin and then the piston actually need to come out?

That depends on what you are or aren't using for a ring compressor.

My ring compressor would not fit in the space between all of the studs, so I had to pull the wrist pin and install the piston into the cylinder, then install the assembly onto the cylinder studs, line up the piston to the rod, and re-insert the wrist pin and clip.

A what now? I am going to try using a tongue depressor because it rhymes with "ring compressor", and it's also something I've heard of before.

Anyone want to come to CT and take this thing, in its present state, away from me for a reasonable price? I really want to ride, and being a mechanic just isn't for me.

A piston ring compressor is a thin band of metal that surrounds your piston rings and presses them into their grooves, allowing you to slide the piston into the barrel (or the barrel over the piston). The one for a Vespa looks like a metal strap wrench and is narrow to allow you to squeeze the rings while sliding the barrel over the piston in the space available.

Google vespa piston ring compressor to see what it looks like and how it works.

Some folks can keep the rings squeezed together with their fingers while they slide the barrel down, but I never could. Or, you might be able to use a wide hose clamp. I broke the oil ring trying to do it with my fingers, and ended up getting the ring compressor.

4-cycle operation in simple terms:

Suck, squeeze, bang and blow.

You're doing fine. Don't lose confidence now!

As has been mentioned, some people can squeeze each ring with their fingers and *gently* work the cylinder over each ring. I can't. If that doesn't work for you either, you can try using the flat side of a small flat blade screwdriver to *gently* compress the ring as you work the cylinder over the piston. It's not that hard, it just takes a bit of patience.

It is probably easier to remove the piston from the rod and do this on a bench, but you can try it either way.

I Googled Vespa piston ring compressor, but nothing specific (to the Vespa) came up…. Does anyone have a suggestion in terms of what I should buy as a ring compressor to allow me to try without (and then with) the piston ring in its current state??