500 ownership driving tip to avoid cracked pistons
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Veni, Vidi, Posti
MP3 500, GTS 250 (both 2008 MY), 2012 Honda NC700 DCT
Joined: 02 Mar 2013
Posts: 5453
Location: Madison, Wisconsin
Tue Oct 08, 2019 9:22 am quote
Hey Stromrider, I dare you to offer to calibrate his dyno!

Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni
Joined: 13 Oct 2012
Posts: 7494
Location: Ashburn, Va. Home to the Internet
Tue Oct 08, 2019 10:12 am quote
jerryd wrote:
since you insist to throw insults:

not only is RPM an important function of a "motorcycle engine oil"
but the fact motorcycles engine oil shares a sump for oil that is lubricating transmission gear sets as well. so yeah, my point is pretty embarrassing for you know it alls. the 500 engine on my scooter is perfectly happy running oils made for cars and trucks that I found to work well in my high performance cars that make triple the output the dealer give us.

when can we stop talking about oil and continue the conversation about low rpm, high load detonation on my 500 mini car engine??? cause the way this thread reads I can picture a newbie coming into this thread because he hears the same detonation I hear. then after reading comments by web-tech and stormrider and go out and purchase oil made for motorcycles. hoping that will solve his problem.
Where did anybody state oil will prevent detonation? Your reading stuff not typed.
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5605
Location: South Carolina
Tue Oct 08, 2019 12:25 pm quote
Madison Sully wrote:
Certainly some data points will be outside the normal (I'm used to that).

It's just that, I have used Shell Rotella T6 5W40 (that diesel stuff), and commuted ~135 miles per day, for about 46,000 miles now.

I *ALWAYS* use high octane fuel (called premium around here, not sure why). And probably 95% of the time ethanol free, not that I think that has anything to do with it.
I got to thinking about this issue again, and it seems like there might be a geographic component to this problem. Most of the complaints I can remember were on MP3s located in the southern parts of the US. It reminds me a little bit about how well Harley Davidson v-Twins ran in WW2, until they got to North Africa. In the southern US, temperatures are higher, and most manufacturers recommend a higher viscosity oil for warmer weather operation. I'm not sure this explains everything, but it might be part of the equation.
Hooked
Piaggio MP3 500
Joined: 21 Nov 2017
Posts: 211
Location: Austin, TX
Tue Oct 08, 2019 2:33 pm quote
Well, after slogging through the translation of the German MP3 500 site, there was some speculation there that low-viscosity oil provided insufficient cooling to the piston skirts, which caused premature wear on the cylinder. Which caused the oil-in-the-airbox problem, from excessive blow-by. I didn't see that it was causing the piston ring lands to crack, really the only citation for piston ring lands cracking that I saw was the one cited earlier in this thread, from detonation. And a cracked piston land will surely cause excessive blow-by.

But there may be a heat component to the problem, whether it's related to the oil changing characteristics or to a hotter cylinder causing more detonation. That's a good observation about we sutherners having more problems with this.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2215
Location: Starfleet Command, South Eastern UK HQ
Tue Oct 08, 2019 11:07 pm quote
Yes, an interesting point raised by Motovista. No doubt this will have some bearing on it. In the UK our climate is still moderate. This may explain why we don't see many piston issues.

Many engines over the years have suffered from cracked piston ring lands. A main cause has been shown to be piston flutter. Another is poor oil quality, and there are other causes too. Suzuki briefly suffered this issue on its mk2 400 Burgman engine but had few cracked piston ring lands. Just higher oil consumption and rattling/pinging noise. It was cured using a new piston using a wider top compression ring which stabilised the flutter curing the condition. Flutter causes uneven combustion & stress accentuating detonation. The flutter also causes exponential piston skirt wear leading to high cylinder and ring wear, higher oil use etc etc.

In the main, the higher the quality of the oil (an m/c oil with good oil film strength & cling) the better the engine is protected from these types of issues, whether it's cause is high heat from geographical or high stress running, or other running issues.

I'm sure Jerry will cure his issues however he does it. He's not afraid to get in there and get his hands dirty and without wishing to sound patronising, he does have some good knowledge on many things. I suspect putting his bike back to standard will go a long way to fixing stuff and should make it easier to fix.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2215
Location: Starfleet Command, South Eastern UK HQ
Tue Oct 08, 2019 11:17 pm quote
Squeazel wrote:
Well, after slogging through the translation of the German MP3 500 site, there was some speculation there that low-viscosity oil provided insufficient cooling to the piston skirts, which caused premature wear on the cylinder. Which caused the oil-in-the-airbox problem, from excessive blow-by. I didn't see that it was causing the piston ring lands to crack, really the only citation for piston ring lands cracking that I saw was the one cited earlier in this thread, from detonation. And a cracked piston land will surely cause excessive blow-by.

But there may be a heat component to the problem, whether it's related to the oil changing characteristics or to a hotter cylinder causing more detonation. That's a good observation about we sutherners having more problems with this.
That's interesting. Usually low viscosity oil gives better flow rate which in turn gives better cooling. But it must be a low viscosity MOTORCYCLE oil. M/C oil is guaranteed to have a very high strength oil film preventing metal to metal contact. Car oil of virtually any spec is inferior, as is Diesel oil. Diesel oil has some of the poorest oil film strength compared to even most normal car oils. Also it can't cope with packaging up the harsh petrol engine carbon which is gritty and hard compared to diesel engine carbon which is soft. That increases engine wear at a much higher rate.

Contrary to popular belief, diesel engines are very easy on there oils inspite of being a high compression engine. Overall they run cooler and rev very very low. As mentioned the carbon produced by these engines is also very soft and as long as the oil dissolves that carbon, it does no harm. That's why diesel oil has lots and lot of detergent in it. Unfortunately that detergent doesn't work well on petrol engine Carbon and it reduces oil film strength.
Hooked
2010 gts 300 super. 09 MP3 500 lite
Joined: 02 Apr 2013
Posts: 441
Location: tampa
Wed Oct 09, 2019 4:57 am quote
there is a second component to detonation that needs to be shared. have you ever wondered why combustion temperatures at 2000f doesnt melt your pistons? cause they melt at 1220f.

have you ever driven your car at 70 mph in the rain? did you notice water drops slowly creeping up your windshield at like 10mph ? why are they not also moving up the windshield at 70mph? the answer holds the key why your pistons dont melt from combustion temps.

the reason I bring this up is because during detonation the natural air barrier created that allows engines to run without melting pistons, is shattered and suspended. vast heat is now entering your piston.

lack of oil quality is not causing detonation. detonation is causing the oil to appear to fail and not do its job.

hope someone gained some knowledge today.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2215
Location: Starfleet Command, South Eastern UK HQ
Wed Oct 09, 2019 7:02 am quote
Yes, that's interesting jerry, and quite right regarding the barrier above the piston. We use that barrier in engine design to allow us to extract more power from the engine without, as you say, melting the piston crown.
Hooked
Piaggio MP3 500
Joined: 21 Nov 2017
Posts: 211
Location: Austin, TX
Wed Oct 09, 2019 7:18 am quote
Interesting point about piston flutter. When I had my engine apart, the piston was the stubbiest thing I'd ever seen. Like 4 inches across the crown but only about 2 inches tall at the skirt. I understand that in general a short shirt makes it slide up and down easier (that sounds nasty), but I think it would contribute to flutter if it's not precisely fitted to the bore. I know I had to get the correct piston size to match my cylinder specs, which came in .001 inch increments between piston types "a", "b", "c" and "d".
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2215
Location: Starfleet Command, South Eastern UK HQ
Wed Oct 09, 2019 10:21 am quote
Squeazel yes, modern pistons are very short skirt mainly to reduce friction and give the clearance needed for conrods & flywheel webs on modern short stroke engines. As you elude to, it can lead to piston flutter, especially as the engine wears it's piston & barrel. This is potentially another cause of detonation in older engines.

The main issue as you will no doubt know is the the piston and bore wear oval in shape. The piston skirt wears too. To help reduce the chances of flutter the skirt of the piston is always reduced in length in the cross plain to the wrist pin (gudgeon pin to us UK types). But as the oval wear increases, the side thrust to the piston and barrel also grows. This increases wear further to the piston and rings and eventually introduces a degree of flutter. This happens eventually on nearly all engines that become worn. It's worse on some designs than others. Over time this can lead to broken rings, pistons etc. And at the risk of sounding like a broken record, the use of the correct oil for the engine, and a good quality one, will extend the life of the engine exponentially by reducing that type of engine wear.

In our testing we showed using a quality m/c oil over diesel engine oil gave an average extra engine life expectancy, across several m/c engine types, of between 35-40%. The difference is huge. That's why I bang on about using the right oil. Even car spec oil reduced engine life expectancy by between 25-30% on many engine types. Big difference. I won't go into all the technical reasons for this as it's lengthy & it's Jerry thread after all. All very interesting.
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5605
Location: South Carolina
Thu Oct 10, 2019 10:02 pm quote
Squeazel wrote:
Well, after slogging through the translation of the German MP3 500 site, there was some speculation there that low-viscosity oil provided insufficient cooling to the piston skirts, which caused premature wear on the cylinder. Which caused the oil-in-the-airbox problem, from excessive blow-by. I didn't see that it was causing the piston ring lands to crack, really the only citation for piston ring lands cracking that I saw was the one cited earlier in this thread, from detonation. And a cracked piston land will surely cause excessive blow-by.

But there may be a heat component to the problem, whether it's related to the oil changing characteristics or to a hotter cylinder causing more detonation. That's a good observation about we sutherners having more problems with this.
And here's something else you can add to the mix:

There are a lot of people who modify the MP3 500 air filter box to let more air in.
The Piaggio ECU takes in information from the Lambda sensor and regulates the air/fuel mixture.
Over 6000 rpms, the Piaggio ecu stops taking in information from the lambda sensor and runs on it's internal program. So at higher rpms, it isn't making any changes for higher air flow.
So at higher rpms, you would likely be running the engine a bit leaner than the manufacturer intended.
How many people who have cracked pistons modified the airbox, and live in a hot place where they are going to be running the bike for long stretches at high rpms?
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5605
Location: South Carolina
Thu Oct 10, 2019 10:18 pm quote
I think collecting this information from riders with more than 15000 miles on their bike would give a better insight into what really causes cracked pistons in the MP3, and whether or not you are likely to have the problem down the road.

Total Miles

Cracked Piston Y or N

Hot Climate?

Rotella 5-40?

6000 mile oil change intervals?

Modified Air Box?

Long High Speed Stretches? (5+ miles at 70+ mph)

Lighter than stock roller weights/sliders?
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2215
Location: Starfleet Command, South Eastern UK HQ
Fri Oct 11, 2019 1:16 pm quote
Nice one Motovista....cool!
Veni, Vidi, Posti
MP3 500, GTS 250 (both 2008 MY), 2012 Honda NC700 DCT
Joined: 02 Mar 2013
Posts: 5453
Location: Madison, Wisconsin
Fri Oct 11, 2019 3:53 pm quote
Answers in quote
Motovista wrote:
I think collecting this information from riders with more than 15000 miles on their bike would give a better insight into what really causes cracked pistons in the MP3, and whether or not you are likely to have the problem down the road.

Total Miles
46,000
Cracked Piston Y or N
No
Hot Climate?
Wisconsin. Southern Wisconsin.
Rotella 5-40?
Yes, since new I think, without exception.
6000 mile oil change intervals?
Couple at 6000, couple at 5000, rest at or after 4000.
Modified Air Box?
Yes.
Long High Speed Stretches? (5+ miles at 70+ mph)
My commute is 65 miles each way, interstate highway 57 miles of it. So, yes.
Lighter than stock roller weights/sliders?
Stock everything in the transmission.
Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni
Joined: 13 Oct 2012
Posts: 7494
Location: Ashburn, Va. Home to the Internet
Sat Oct 12, 2019 5:57 pm quote
Total Miles 59,975

Cracked Piston Y or N No

Hot Climate? Mid Atlantic/Virginia. Hot humid summers

Rotella 5-40? Agip Scooter City 10w-40

6000 mile oil change intervals? 5,000 average

Modified Air Box? No

Long High Speed Stretches? (5+ miles at 70+ mph) No 70+ MPH for long periods.

Lighter than stock roller weights/sliders? 16 gram Dr Pulley Sliders. Average 6,000 RPM down the road.
Hooked
Piaggio MP3 500
Joined: 21 Nov 2017
Posts: 211
Location: Austin, TX
Tue Oct 15, 2019 7:46 am quote
Total Miles 45,000

Cracked Piston Y or N Yes, was cracked when I did the top end.

Hot Climate? Austin, Tx, so yes.

Not sure about oil- Was BubbaJon's scooter. I use Valvolene 20w50 synthetic

6000 mile oil change intervals? 5000

Modified Air Box? Yes

Long High Speed Stretches? (5+ miles at 70+ mph) Some 20 minute 70+ stretches, BubbaJon would know more about early history.

Lighter than stock roller weights/sliders? 19 gram Dr Pulley Sliders and a Fuzzy washer.
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