MP3 500 possible piston ring blow by
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MP3 500 HPE
Joined: 24 Feb 2021
Posts: 3
Location: Oahu, Hawaii
Wed Feb 24, 2021 7:52 am quote
Noticed that my 2017 MP3 500 was reading way lower on fuel economy, usually around 50-55 mpg, and was getting around 4-16 on acceleration.

Checked oil and the case was past full! Smells heavily of gasoline as well. Oil color is still good, just changed it about a month ago.

Google search yields lots of different possibilities, mostly centered around piston rings not sealed.

Anyone ever change these out, or have a similar issue?
Hooked
2015 MP3 500 ie Business
Joined: 29 Oct 2019
Posts: 365
Location: Belgium
Wed Feb 24, 2021 11:38 am quote
The Master engine on your bike is known for sometimes cracking a piston ring, BUT that is usually caused by abuse (excessive/extensive high revving) or using the wrong fuel grade. The bike is designed run on premium fuel, at least if you are in the US. That means 91 or 93 (R + M)/2 in the US or 95RON minimum elsewhere.

If it does need a ring job, it is a sign of a very badly/poorly maintained bike and probably has issues outside the motor as well.

Just FYI, I do a oil+filter every 3.25Kmi/5K km on the trot even though Piaggio states double that. Oil is cheap, engines are not. Also it requires a motorcycle rated (MA/MA2) oil in a 5W-40 weight. I use the factory spec'd Eni/Agip stuff, but Liqui Moly also makes a Piaggio approved version.

Using the wrong oil can cause excessive engine wear.

Also be sure the CCV (crankcase ventilation) works perfectly.
Hooked
Piaggio MP3 500
Joined: 21 Nov 2017
Posts: 303
Location: Austin, TX
Thu Feb 25, 2021 1:05 pm quote
I've changed the piston and rings in mine. It was a big job, but I kinda doubt that's your problem. You have gas in the oil- and that can come only through the fuel injector.

There was a problem with the 460cc Master engine where the thermostat would never let the engine get up to temperature, and when owner's driving habits were short trips, the engine would never get to temperature and the oil would hold onto the excess gas that the fuel system would pour into the cylinder, the ECU thinking the engine was cold and needed a richer mixture. It wasn't much of a problem until the plastic oil pump gear would get degraded by the gas in the oil and the engine would explode from lack of oil when the gear failed. So, if you tend to take short trips, I would check the thermostat for proper operation. Or just replace it, it's cheap.

Other than that, maybe you have a fuel injector leak or overpressure on the fuel pump dumping too much gas into the engine. But I would look at the fuel system next, before assuming it's rings.

If you really think the rings are the problem, check the airbox for oil- that's the classic symptom of needing rings or a piston- the airbox will be chock full of oil (and the dipstick will be low).
Lurker
MP3 500 HPE
Joined: 24 Feb 2021
Posts: 3
Location: Oahu, Hawaii
Tue Mar 02, 2021 10:16 am quote
Awesome, thanks for the feedback! I do fill her up with 92 octane only and just had the oil changed about 200 miles ago.

Checked the air box (they have a small tell-tale bubble now) and it was gummed up pretty hard from too much filter oil and had a lot of road boogers in it. Good soaking in K&N solution and light coating of red oil.

I also changed the oil again and checked the pre-engine filter sleeve. No evidence of material.

She’s running cleaner now and will check the fuel supply and injector.
Hooked
Piaggio MP3 500
Joined: 21 Nov 2017
Posts: 303
Location: Austin, TX
Wed Mar 03, 2021 7:53 am quote
OK, maybe a gummed-up air filter would do it too, now that I think about it. Good catch. Might be a good idea to run some seafoam through it, and clean the throttle body too, as long as it's open. May not need any parts, just a bit of cleaning. What's the mileage say now?
Lurker
MP3 500 HPE
Joined: 24 Feb 2021
Posts: 3
Location: Oahu, Hawaii
Mon Mar 08, 2021 11:22 am quote
Thanks so much for all the feedback! Had me scared when I started reading about the cracked pistons. Reading about these issues is like WebMD, when you have the sniffles and it sounds like the plague.

Mileage is still really low, almost at 3,500 miles. Still running clean and no issues with oil smell or level increase in the sump. Will do another tear down soon and post some pics.

Mahalo guys!!
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