Modern Vespa

They don't last forever, but they sure lasted long enough!

MP3 500 uses two plugs in one cylinder.
Recommended change interval - 6,000 miles.

I don't recall the thread, but it was recently brought to my attention that I had not changed plugs in my MP3 in, well, a few years. Four years and three months, actually. And just shy of 30,000 miles.

Just changed them today. Came out smooth, no problems there. Little bit of brown/black soot, but not much buildup. I was a tad surprised at the wear of the ground, but hey, I certainly got my money's worth out of these little buggers!

My understanding is that you need to wash your scooter with every other plug change.....

Ah, good to know I have another year or so to go on that one.

By the way, the plugs are NGK CR8EIB-10, aka NGK 4948. I add this because I have found that the plugs with the screw-off nut at the HT lead end can wear out, resulting in a cap that pops off at the worst times. Photo below is of such wear; don't let this happen to you!

Those sure look worn out and well overdue for replacement. Not good for your cdi units or engine efficiency. But you know that.

Yeah. Oops.

My father had a Vanden Plas R, with a Rolls Royce engine. Bought it from a friend and had it for years. It started running a bit rough, for a Rolls Royce, so we took it to a local mini tuner for a look see.

Six plugs all without the ground electrode!

These scooter sure are hard on plugs. I had a set in my truck for 50K miles and they hardly looked worn.

Tierney, has you truck got 'long life' spark plugs? These are specified by some manufacturers as they can go for very long periods without renewal. Quite often the life span of those plugs can be 40-50,000 miles on cars but slightly longer on trucks. The look of the plug is no real indication of how worn a plug is. So even if the electrodes look ok, the plug can be worn out.

On bikes the number of miles the spark plugs cover before replacement tends to be less as our engines rev anywhere between 3-5 times as much as car engines for most of their lives. So my car uses similar plugs to my bike. My car spark plugs only need changing every 40,000 miles. But my bike needs them changing every 12,400 miles. It's purely down to how many times the plug fires per mile covered. By 12,400 miles my bike spark plug has fired as much as the plugs in my car at 40,000 miles.

Unfortunately, if you go over the recommended miles before replacing the plugs, the resistance inside the plug increases so much that the plug can require 2 or even 3 times as much voltage to fire the plug. Of course, your bike cannot supply 2-3 times as much voltage so the result is you get a smaller spark initially, which equals less power, less mpg...etc. Then you start to get misfires which ruins catalytic converters. It also puts a huge strain on the cdi or coils of the bike making them run very hot leading to possible, or probable earlier failure.

I know you know all that as you are a top poster with good knowledge. Only saying this to help newbies and anyone who isn't sure about what happens when you run spark plugs for too long. Yeah, I know. It's another long post!

Good points Stromrider.
Basically means the spark plugs went effectively more like 120,000 miles if they had been in my old Focus.
I felt no driveability issue, but then, my butt dyno hasn't (ever) been calibrated.

Proof of how strong modern ignition systems are.

And another good point SCTLVR. Ignition systems have come a long way.

Are you saying you need someone to fiddle with your butt!!

I guess so....

Your truck isn't going down the road at 6,000-7,000 RPM

Spark plugs and oil are the cheapest ,and easiest things you can do to keep your engine running smoothly.

so... irid plugs are good for ~30K mi on the scooters. got it, thanks OP.

Or was that not the point of the post?

Or higher. Have a few miles under 60,000 on my MP3 500 and can't find any documentation on when they were changed last. So might be close to 45,000 or 50,000 miles. Put the iridium plugs in and don't think I have ever changed them. I was always told on cars if it is running smooth and getting good gas mileage, don't worry about the plugs.

Yes but with dual plugs you have to wash it twice.

Just one data point is all.

Posts need to have a point?

I read an interesting piece on my Autoweek daily messages about knock off plugs flooding the market.

They were advertised on Amazon at about half the retail rate. They look very close to the real plugs , but there are differences starting with the packaging.
You need a sharp eye to see the difference.

The buyer went to a reputable auto parts store and bought a set , they had the same bar codes on the packaging. But he was curious about how they could be half price. via Amazon.

The guy that bought them contacted the manufacturer and they went as far as looking at the lot number. They determined that they were knock off's .

Simple things like the crush washer being loose on the plugs , the box being slightly larger etc.

Be careful , the dirt bags are out to get your money.

Guess I will be going to the auto parts store to order plugs from now on.

The problem is that the most modern scooters have control units that read many values ​​from the whole engine, spark plug (in Italian it is called "candle") included; in normal conditions it may seem "visually" good but it is its conductivity that influences the operation of the engine. Some time ago there was a Bosch scale in which there was the "heat degree" of the candle, it was cold or hot; if the grade was 225 it indicated that it needed 225 seconds to dispose of the heat generated by combustion.
Now ... the thermal stresses in thousands of miles from the materials that make up the spark plug (excuse me, candle comes out ) decrease its efficiency. Ouch! When i write in technical English i get ridiculous terms and combinations, sorry.
Among other things, the first to suffer from this is fuel consumption, not much on a unitary level but overall it affects; then ... if the flame front inside the cylinder is not homogeneous, the engine cools badly and the lubrication is also more affected, heating it down and degrading the oil more quickly.

I learned a whole lot about spark plugs back in the day as a club level / AMA racer.

There was a guy from Champion spark plugs who attended many of the bigger races ( Daytona 200 ) , you could pull your plugs after practice and he would look at them through something like a jewelers loop. He would say things like too rich/lean, go up a notch on the carb needles etc:

We were mostly running two stroke motors at the time so plugs and jetting were very important . He would hold a small group talk with us in the garage ,or in our case the dirt lot . His knowledge was very valuable information.

One thing he said time and again , fresh spark plugs and motor oil are the cheapest things you can do to help prevent motor failures and improve performance.

Believe me when I say it pays off in the long run, my experience seizing a piston on my TZ250 on the high banks at Daytona once was a very expensive lesson, and it hurt a lot too.

what is factory gap? I order new pugs based on the pictures of how big those used plug gaps look. and the gap look huge. then i get the new plugs and the gap also look huge.

had a nice running 1972 triumph gt6 many moons ago. one day it stop running while driving it. stopped like it ran out of gas. no misfires or nothing. just a smooth stop. early learning experience

the plug gaps had burned the gap so big the plugs could no longer fire
used gap .070
new gap .028

this thread is missing factory gap specs.

Most interesting 15 minutes I've ever spent learning about spark plugs.

"https://youtu.be/smIqDKTm2hE"

so I got a pleasant surprise today. my bike didnt have good quality plugs in it. had crappy plain copper plugs. and worn too. must have been put in in the first 6000 mile service.

I used to have to hold the brake lever at stops to quell the vibration in the bars. now there is hardly any difference pulling the lever. Its like four times smoother. no more shakey mirror. small dash rattle gone. it runs smoother everywhere in the power band. I cant believe how smooth it actually got. It feels faster and pretty sure it actually is. I have a whole new appreciation for this power plant. I feel like I just traded my ten year old bike for a new and improved model. just tickled pink here. wow.

look at the insulator difference. both heat range 8 plugs.

Hey Juan Orea, is that spark plug video available on You Tube ?

It won't open on my computer and I'd like to watch it and learn more.

Very interesting. Thanks!

Using Chrome?

Try a different browser....

As mentioned previously, given the different browsers used not all videos show up for us to click and watch. Please copy the link in the body of your post so we have the option to cut and paste. Thank you.

Sorry, post edited to include link in text. And here.

"https://youtu.be/smIqDKTm2hE"

From what I have been told plugs are set when they are manufactured and you do not change gap any more. Some plugs the side electrode will break off if you try adjusting them.
Learned that when I was turning wrenches for GM dealership around 2002.

Tip: You can pick up iridium plugs at a regional NAPA auto parts store off the shelf for a reasonable price. Buy at least two while you are there.

OOOF. These NGKs are ~$10 from Napa/Oreilly... Is there plat versions that's half as much? I don't think I'll ever hit 30K mi on this scooter.

edit, from NGK: https://www.ngk.com/product.aspx?zpid=9674 :
Longevity: 100k Miles

lolol. is there a mp3/bv3 even remotely near 100K mi?

funny when this thread popped up I went shopping around for plugs. that led me to reading feedback on the iridiums on amazon. there where quite a few claiming their vespa 300 were faster after plug change. at the time I was thinking cool but placebo.

now I am a firm believer and writing them. sparks plugs indeed wear out faster in small higher rpm engines. now I think the rpm think is exponential. so after changing the plugs on the 500 and picking up ridiculous smoothness and power (like two bike lengths to 60mph), I changed the plug on my 300. used the same cr8eix. bike also did not have an iridium in it. the difference it made was equally exciting. so much smoother running.

I already knew from tuning cars the value of iridium plugs. the 4g63 turbo engines I play with when tuned to high HP wont do a clean pull with regular plugs. miss fire bad through half the pull. screw in a set of iridiums and it pull clean to any rpm. I also found if you were tuned with 8 range plugs it can cause detonation going back to 7 range. the plug itself would get too hot during hard pull. unfortunately there is no such thing as a dual heat range plug. and that is what turbo engines need. with 8/1 compression the engine run great with heat range 6. under 30 psi boost it need 10. I tried running 9 but they foul out after 200 miles. the coldest I can run is the 8 range. its just the best compromise.

but yeah. drop some iridiums in your scooter.

NGK 4218 - CR8EIX IX - Nickel ground electrode with threaded stud. .8mm gap. Longevity: 50k Miles

NGK 4948 - CR8EIB-10 - Platinum ground electrode and solid stud. 1.0mm gap. Longevity: 100k Miles.

NGK 5258 - CR8EIB-9 - Platinum ground electrode and solid stud. .9mm gap. Longevity: 100k Miles.

This is my thinking as they are easy to change in a scooter and less likely to be knock offs.

At 100k miles lifespan why don't they just build them into the head?