Modern Vespa

Last year, when the dealership in Richmond found the crack in my just-over 6,000 mile MP3 500, I promised pictures. I dropped my BV 350 off last week to have the damaged front shield replaced and they had my old 500 piston on the shelf waiting for me. The crack likely occurred at around 4,000 miles, but I didn't drill down to the problem until after the warranty had expired. Piaggio, of course, doesn't see this as a problem they need to fix. (BTW...Scoot Richmond did another MP3 500 with a cracked piston before mine.)

Following are photos of the piston crack:


The crack is just to the right of the red mark, under the compression ring. Doesn't look like much...

...so you use a screwdriver blade to deflect that part of the piston up and this is what you get. (Ice cream stick used as a wedge.)

Then deflecting it down. The red mark to the right indicates the point at which deflection was no longer easy, though it is logical to assume the crack extends a little farther.

The top of the piston. The visible crack is shown by the little yellow mark between 12 and 1 o'clock. The last point of deflection is anti-clockwise to near the 10 o'clock location.


Last edited by LJClark on Mon, 20 May 2013 10:10:50 +0000; edited 1 time

So what were the symptoms of this cracked piston?

My cracked showed up about that same time between 6,000- 8,000 miles. BTW these cracks have only appeared on the 500. Mine was also a 2009 MP3 - 500

The loss of power was minimal at first. But you can't avoid noticing the oil gushing out of your air cleaner. On an 18 mile trip to work, I filled up 1/3 of a water bottle with oil.

So you mention power loss - any way to give a relative measure? I know it's been awhile...

You should know how your scoot feels when you hit the throttle, well when the power loss started to show, I was at full throttle and barely keeping up with traffic.

Reason I ask is because I am getting the oil issue (fixed by a homebrew solution) but I have no power loss, no smoking - absolutely nothing to indicate a mechanical problem. I still zip right along at 80 mph all day long.
Quite a mystery but when I get another bike I plan on tearing it apart to figure out why. But for now it's my daily transportation.

Look back at that loss of oil thread, and the facts will be much more descriptive. Since the fix, the scoot throws no oil and feels great.

Maybe the up/down high rpm of the piston exacerbates the oil leaking, loss of power. But still it seems strange the piston would only crack there.

Waitadamminnite. It just impinged on my brain what you were showing - that friggin land MOVED when you pried on it. WFT?? That means that for a large part of the circumference it has no support. Most pistons are designed to where there are small slots undercutting the land but nothing I've ever seen would allow the broken land to deflect. What a POS design... I'd bet the new ones aren't made like that.

What happens first, the crack or the separating of that part of the piston from the rest of the piston?

My local shop never showed me my piston, but it was cracked ;(

I would say the later. Then the separation happened from the constant flexing at one spot ultimately leading to metal fatigue.

My money is on a bad batch of pistons - a bad set of forgings with pre-stress cracks already present, and we're just exacerbating it with high RPM/power runs.

Mine is throwing oil but like Bubba's - it still accelerates plenty fast (as confirmed by riding partners), mileage is about the same, and I get no smoke during operation. So for now, I'll run with my oil separator.

When it starts to go, I'll get it rebuilt - and I bet the newer forgings are a lot more robust (based upon the results of those who've done the rebuild and not had any problems since then).

[quote="Shanghai Dan"] My money is on a bad batch of pistons - a bad set of forgings with pre-stress cracks already present, and we're just exacerbating it with high RPM/power runs.



If this is true Piaggio should back this fix whether it happens under warranty or not. It would be nice to know how many piston issues like this have occurred. Unless these incidents are reported to the NHTSA nothing will happen for the customers.

Last edited by norCal Randy on Tue, 21 May 2013 02:00:07 +0000; edited 1 time

Mine looked worse than that when the dealer took it apart last year. OAD may remember. I'll see if I can find the pictures and post them. Luckily for me it was just under warranty and Piaggio covered it.

Bubbajon...When you look closely at the area behind the deflected land, you can see the "grain" of the casting. I might see if one of the photos will blow up enough to show that clearly.

And as I noted under the photo of the piston top, the yellow lines mark where I was able to put in a screwdriver blade and get some obvious deflection of the land. I'd bet that if I grabbed the free end of the land with some pliers and pulled straight away from the piston side, I'd reveal almost 90 degrees of cracking.

I'm not sure this falls within NHTSA reporting parameters.

I'd also be willing to go out on a limb that Piaggio has decided that this is a stonewallable issue. Nothing but expense to be incurred if they volunteer to make good on some or all of the resolution. Very difficult to calculate monetary value of "good will" for such a little issue as a batch of cracked pistons, even though it cost individual customers $thousands.

About 5 years ago Moto Guzzi(part of Piaggio now) came out with a new MC with hydraulic valves instead of what we have(screw/nut). Later a # of these sold models had hydraulic valve issues. In the end all bikes with that design were rebuilt with improved parts whether the bikes were still under warranty or not. Who contacted NHTSA I don't know. Like MP3s there weren't a lot of this model sold in the USA. MG(Italy) only makes about 7K different models of bikes a year sold world wide. Some other new MGs had so many defects new that some owners used the 'lemon law' to get a replacement of X bad model as a compromise. Aprilia was the owner of MG then and I'm sure they didn't want to cooperate with the US Fed. Govt., but they did whether they wanted to or not. A mfg. doesn't make these kind of recalls, the NHTSA does and the mfg. has to comply. Go to NHTSA website and see for yourself. Squeaky wheel get's the grease.

Last edited by norCal Randy on Tue, 21 May 2013 03:33:27 +0000; edited 3 times

The best I could do with a low res jpeg and 800 x 800 limit.

Sorry...I couldn't find an NHTSA recall related to Moto Guzzi valves -- Just a manufacturers recall. I did find an NHTSA recall for forks in the same year range.

NHTSA: "Generally, a safety defect is defined as a problem that exists in a motor vehicle or item of motor vehicle equipment that:
-- poses an risk to motor vehicle safety, and
-- may exist in a group of vehicles of the same design or manufacture, or items of equipment of the same type and manufacture."

Also: "Examples of defects NOT considered safety-related:
<snip>
-- Excessive oil consumption."

I suppose that if several MP3 500 piston failures resulted in drive train lockup or something similar, that might prompt a safety investigation.

The other option would be a complaint to EPA based on emissions...But I wouldn't hold my breath (pun intended).

You should have waited 35 minutes...

These are the same photos, with a 1400 x 400 pixel crop, then down-sampled 50% (700 x 200) with PhotoShop's "save for web".


Closeup of the area behind the separated piston land.

Yeah. that's a defective casting, probably too much phosphorus in the steel when cast. Makes it brittle and subject to cracking. Ick.

On the other hand, replacement piston sets (piston, pin, rings) are around $60, so other than the labor to rebuild it's not too expensive. HOWEVER, there are four different pistons! Which size to get? Do they go up in size from 8738110001 to 8738110004? If so, I'll just order the largest one, and hone out my sleeve to fit if needed, when I eventually get it rebuilt...

Aluminum.

And it was certainly the labor that brought up the repair cost. Since I was selling it on consignment, that just lightened up the final check.

[quote="LJClark"] Sorry...I couldn't find an NHTSA recall related to Moto Guzzi valves -- Just a manufacturers recall. I did find an NHTSA recall for forks in the same year range.



Of course you didn't with that question. It's probably listed as a MG model, not whether as a valve issue. I'm not making this stuff up. If you want ask a long time MG dealer about it, like MPH in Houston, Texas.

Nope...I started with the NHTSA online database and looked at every Moto Guzzi recall, model by model, from 1991 through 2010. I could not find any NHTSA recall related to valves. Headlights, oil hoses, cracked forks, connecting rod bolts, top case mounts, etc. -- sure. Other online sources point to the valve issue being a manufacturer's recall.

Given that level of grain - looks almost like pot metal - I'd say that was a crappy casting. I've seen that sort of thing way too many times in stressed VW engines and heads. What typically happens if the alloy is too cool is the "thin" parts cool faster than the denser parts leading to a form of stratification.

Just because there is a recall doesn't mean that the Feds are involved. Usually the Feds are only involved if there is a immediate "safety" concern. There are a lot of manufacturer "recalls" that are not mandated by the Feds. They do this as a means of customer support and "honor" if you will. You can learn a lot about a company by looking at their voluntary "recalls" or ccampaigns. There are some well known motorcycle companies out there that have major safety issues that don't offer and relief or recalls federally backed or not. While others with the same issues have issued voluntary campaign. A HUGE difference between corporate policies.

This thread scares the hell out of me. I bought my scoot used and tried to avoid the 2009 model year. Of course, what year do I end up buying? 2009.

I called a few Piaggio service centers in my area (Chicago) and none thought this was a widespread problem. Maybe they were wrong.

There are thousands of Master 500 engines out there running just fine, there just not in the MP3, the BV500 uses this engine too and don't see high failure rate on them either. One bad batch of pistons doesn't condemn the whole lot.

exactly.

But there IS a problem with some of these pistons - from the photos I thought it was failed steel because (like Bubba) the graining looked like what you get in bad steel. If that's aluminum, it's a really bad batch of aluminum.

That said, I've been monitoring my oil blowby (thanks to my Jegs oil separator), and I'm seeing about 1 fluid ounce per 100 miles at 5000+ RPM. So it means I'll blow a quart of oil every 3000 miles or so. Given that I capture the oil, and it's pretty darn clean, and I can just dump it back in the engine, I'm not that worried, yet. But if the rate increases dramatically I'll look for a rebuild.

However, if Piaggio batched the production of MP3 500s, and directed a run (or a partial run) of Master 500 engines towards any of those MP3 500 batches, then the bad batch of pistons could be concentrated in the MP3 500s. Or not.

So there is really no satisfactory answer/conclusion. Several variables could line up to focus the problem, or they could line up to scatter the evil seed of bad pistons across the globe.

But, how many cracked pistons have we seen, maybe a 1 or 2 dozen? This is out of thousands of motors.

For this reason alone I would contact the NHTSA about my piston loss.

That's just here. I saw a reference on some German site that they also have noted more than a few cases of this crap.

the cracked pistons are few there are more with broken piston rings i've posted earlier in the oil thread that the problem of loosing oil is or the Piston or the Piston rings


somebody posted that the Bev uses the same engine that's not correct the Beverly 500 uses a 460cc and later in 2009 Piaggio fitted the 492cc twinspark for modelyear 2010

the new mp3 500 (400 Bodystyle) doesn't have any problems with the piston this one is sold the most in Europe some have broken piston rings due not driving it warm enough before going full throttle

Thanks Maksor!

That said, which piston is recommended? Should I just for the biggest (I believe the one ending in 4) and hone out the cylinder to fit?

you most buy the set Piston and Cylinder if you don't know your current Cat for the Piston other wise it won't fit a 10th of a mm to big or to small


the Cat 1 to 5 is a number for the size could be hight differents or wide

Hmmmm..............I wonder if those that recommend you should "ride it like you stole it" when breaking it in have anything to do with this.