Modern Vespa

no issues with mine.

You can not hone out the cylinder to fit a new piston it has to be bored out at a machine shop.
You need to find out what your bore is now and order the piston accordingly, machine shop can help out with this. But they will need Piaggios Cylinder specs to know what the tolerances are.

I wouldn't discount the possibility that someone was a little to aggressive installing the rings on the piston or installing the pistons in the cylinder. The ring shelf is meant to be evenly loaded. You place too much force on one area and what you see is what you'll get.

Maybe Guido was a little hung over that Monday morning....

Sorry, but in all my years of working on engines I have yet to see a land broken from rough handling. Rings yes, lands no.

Yea, I know. You'd have to try to hammer it in the cylinder to break the landing. I'm thinking it only fractured it and fatique took over from there. When I first saw the photo I thought it was a broken ring...not too uncommon like you say.

Just trying to figure out why there's a problem with so many pistons in the same part of the piston. The failure looks to be on the wrist pin axis, that's typically not even the most stressed part of the piston. It also isn't on the exhaust valve side, judging by the scorching on the piston, so that's not a clue.

Bizarre.

I had a racing MINI Cooper that developed play in the bearings. It vibrated the piston (aluminum alloy machined to minimal weight - i.e. "fragile") to the point they shattered. As tough as pistons have to be, they don't respond well to unexpected loading.

Not sure if you've ever seen a motor being build at a factory, but they make it pretty idiot proof to break something.

We had a racing mini too back in the 70's. Had a rare Cosworth engineering head, Racer Brown cam and headers. Sure miss that little rascal.
I would assume that they use the sleeves to insert the pistons tho granted I've had my fair share slip out and hang. Anyway - these are broken bottom lands - you couldn't do that hammering them in.

Unless the ring compressor tool didn't...compress that is. Then the ring would hang up on its way into the cylinder during initial assembly. Normally if you try to force it in its bad news for the ring, but if the landing happened to be machined too thin and it's loaded only in one small region?? I could see them getting damaged. Never heard of it, but I've never dealt with Piaggio pistons before either!

Not sure if you've ever seen a motor being build at a factory, but they make it pretty idiot proof to break something.

No. but I've owned Fiats and Alfas all my life. Nothing is done like you think it is!

Especially those danged Fiats. I was once offered a painting to rebuild a famous painter's Fiat. I turned him down. While i regret the decision, I'm still not convinced it was a bad decision. The artist was Max Shertz BTW - when I lived in Marin County, CA

Far as I know all the MP3 motors have Nigusil cylinders that are very hard and if you hone them the rings won't seal. It may be the cylinders are OK even after this ring fiasco.

Last edited by norCal Randy on Fri, 31 May 2013 21:55:20 +0000; edited 1 time

They don't use a shop type ring compressor. Factory's use a tapered ring compressor in most cases not a band type compressor.
You lube the piston up and push the piston in and the rings are compressed as they are pushed in the ring compressor and right into the cylinder.

Shops use a band type because it fits multiple piston sizes and they can damage the rings or piston if not used right.
Factory is installing one size piston so they use the better tapered design.

Nah piaggio sprays a little grease in and put them in by hand its easy done it lots of times its easy no need for special tools just press on the rings and slide it in

These failures do seem consistent with excessive load on the top ring at high rpm. The problem with running in a high performance automatic scooter is that the only way to get to maximum rpm is at maximum speed. Some people will never do this and others will not want to do it during running in. With a manual gearbox the engine can be progressively revved at relatively light load which is ideal for running in.

It does seem very possible that a ridged cylinder will cause high load on the rings at maximum rpm, particularly when the bottom end loosens a bit and the oil is hot. Is there a measurable or detectable ridge in the failed engines?

Hi All, I see this is an old thread but as it came up in my search and I think my feedback may be of interest!?

I have a Gilera Fuoco 500, same motor as the MP3 and today I'm on my 3rd cracked piston now, at 24,500km
First one was on 17,000km then 20,000 and now again!!

I've never seen the piston land fracture on a 4T motor before, but have seen plenty on a 2T. From my experience the land normally breaks under extreme load caused by Detonation.
On the 2nd rebuild I had the ECU software updated and thought this may solve the issue of possible detonation, but clearly not!

I'm awaiting a reply from Piaggio as to what can be done to resolve this issue?! If I get any reliable feedback I'll share it here.

Have any of you replaced your pistons with a Malossi? I'm thinking this may be my next route to take, your opinions?

3 cracked pistons!? Holy cow. Yes some of us including me have experienced similar but not 3. I am thinking you might have something else going on.

Here is what happened to mine. Got the engine dropped today. Head off. NOW GOOD NEWS!

Also, can you post the manufacture date. On US models it is on the plaque on the right legshield. See 500 owner's input wanted

Welcome to Modern Vespa BTW.

Thanks for the welcome! Apologies for the non-introduction, I'm new to Piaggio brands and this forum, obviously! I'm on several other bike forums and only post relevant posts as I'm too busy to spend all day on forum chit chat!

My Fuoco is listed as 2007-2013, mines a 2012

I see your piston looked like my first one!
The 2nd time round I pulled it apart when it wouldn't accelerate and spluttered. On inspection, my air filter was so filled with oil that it couldn't breath!
After stripping it was cracked like in the picture. So I caught it before it could disintegrate again. This time round I noticed massive amounts of oil leaking out the airbox again. The bike was riding fine with no signs of power loss, but I know it's blown again!
Motor is out and will pull the head off tomorrow and post a picture.

I would just like to get to the bottom of the issue as it's getting flipping expensive now!!

Seeing you are from S Africa I have to ask, are you using a 100% synthetic oil that meets Piaggio specs?

Yes, the bike is serviced regularly at the dealer and they use 100% Synthetic Agip oils.
We not that far behind in tech, We a 3rd world nation with 1st world products!

Just know some places it's not possible to find the correct fluids.

I hear you. Something is amiss there. I hope that the replacement I have coming holds up. Others here have had good luck.

Ok, so the motor is stripped and as I suspected, the top ring land is cracked vertically again, as well as separated from the piston longitudinal. Almost in the Identical spot to the last one?! *Sigh!

Now I wait...


Cracked Again, same spot!

Arrow to Exh side.
Star is where crack is.

The bore and ring condition is what needs investigation. My theory would be that excessive load ( in the direction of the bore axis) is being placed on the piston ring, most likely at the very top of the stroke. The bore may be ridged or distorted or just tight. Also worth checking the piston ring gap at the highest point in the bore.

The excessive load is definitely what's causing the fracture, but Why?!
Normally Detonation causes this, I've seen it on Motocross 2T motors, but the bike is completely stock so why does this keep happening every 4,000 odd Km's?!
The cylinder, piston, rings and gaskets where all replaced with new. The Cyl head is stock, no skimming done. Ignition is stock and the ECU mapping is of the latest update.

If I don't get a positive solution from Piaggio then I'm going to run a thicker base gasket to drop the compression and change from unleaded fuel to lead replacement. Maybe this will solve it?!

I sure hope the New MP3/500's coming to the US don't have this Defect. I can't imaging this being caused by User Error?

Keith,
Marietta, GA

If the cylinder has been replaced then it becomes hard to explain. How about incorrect torque on the cylinder head bolts? If these are overtightened bore distortion could occur. Assuming piston ring gaps were OK then method of assembly could play a part. No undue force should be needed in fitting cylinder to piston and the ring compressor should be tight enough to compress rings without gripping the piston.

I would have thought that any fuel related issue (detonation) would show on the piston crown and also with a single cylinder engine misfiring (pre-ignition or pinking) is immediately noticeable as a loss of power.

It's definitely a puzzling issue!

The rebuild was done every time by the Dealer with genuine parts. I have all the old parts.
If I remember the head torque is 7nm then 10nm then 90deg and another 90deg.

Hope to get some sort of solution from the factory on this, hopefully on Monday!?

Are you getting new old stock as replacements or new Mfg. Parts you may want to check that out if you haven't already done that.

The manual I have says 7Nm in crosswise fashion, then 90 degrees twice, in crosswise fashion.

I really have no idea?!
I'm actually thinking of fitting an aftermarket piston kit but I haven't found one yet?! I was hoping Malossi would have, but no luck, they only have performance camshaft and drive parts.

Ok my guess was close!

Sounds like mine - I use mine daily so have not been able to rip it apart. I've had the oil issue for 17,000 miles now. I made an oil trap system that seems to mostly work but I know I need to get to the bottom of it. Right now I'm able to cruise at 80 mph no issues. I put a pressure gauge on the breather and have seen in excess of 20 psi in that tube - shazam!
Welcome to the forum! If I'd had 3 of these I'd have Piaggio president on speed dial.

Just sharing my experience with cracked ringlands.

On a direct injection engine, we have had ringland failures due to a commbination of:

1. Fuel wash-down of cylinder wall stripping oil film.
2. Unbalanced intake air flow aft of intake manifold, causing one cylinder to run leaner than others when overall tune is leaned out.
3. Improper use of methanol/water injection.
4. Not using fully qualified oil [ironically, my direct injection turbo car also uses T6 as the best oil to battle fuel dilution].
5. General overheating, which exasperates all of the above.
6. Not running proper fuel.
7. Overly aggressive tuning.

In our scoot, I believe it's mainly a heat management issue. But I also wonder if it could be a combination of small tank not being able to "get" enough higher octane fuel through a shared hose...adding high compression...and it gets hot and detonates.

There is a 3 - 4 month period through 7 years of production of the Master engine that are showing this issue, not sure where you are coming up with this as a heat issue
It has been stated there was a bad batch of pistons and the failure pattern seems to verify that.

And don't have a clue what you're talking about octane not getting through a single pipe

Isn't there someone with a 2012 experiencing this issue repeatedly in the UK?

Don't have a clue about shared hose?

I have a 2008...how do you check for the piston manufacture date?

You go by the manufacturing date on the VIN plate in the US.
Check this threat out.

And the guy with a 2012, it's not the same issue, he has had multiple failures. I bet his issue is in the lower end of the engine that is causing an issue with the top end.

Check out this thread, 500 owner's input wanted

Sorry for the late feedback on the Fuoco...

Without any concrete help or information from Piaggio, we went ahead with assembling a new piston and cylinder kit, but we ran 2 of the 0.8mm base gaskets to drop the compression ratio.
0.8mm is the thickest and was the only thickness available in the dealers stock. So it's on maximum thickness base gaskets.

The motor was immediately much smoother and no noticeable change in performance. Scoot still runs sweetly!

I'm please to say that the bikes now run for 5600km without any further issue! Yes we ride A LOT!!
Had an oil change 1,000km after the new topend and again now, and all good sofar!

Ok - that's officially enough of the BS from Piaggio. They have to know something is going on and to expect the owners to suck up the costs is just unconscionable. I wonder how you go about initiating a class action suit - first the steering bearings, now pistons.

Bad cast, Monday morning start up ? I found my oil usage was to much oil soaked into air filter. OEM 50/50 gas and oil works best for me. Back to piston crack replies.

Solution would be a forged piston:

http://www.protoxide.eu/it/categorie-prodotti/1040-pistone-nexus-beverly-500cc--94mm.html

Little pricy though

That one won't fit on a mp3 its for the older 460cc bored out with a 69 stroke

The nexus is never produced with a 492cc twinspark only with a 459cc