The Honda PCX / Forza / ADV150 / SH Forums

Hi everyone,

Curious if anyone has upgraded their spark plug from the stock one? I recently installed an NGK Iridium in my 50cc Metro with 11k miles and immediately noticed a difference in smoother idle and better acceleration. Wondering if I swapped out on my PCX from the NGK CPR7EA-9 to the CPR7EAIX-9 Iridium, would there be an improvement? Mostly looking for mileage, but power is always nice too! What have you all found? Only $9, but always like the group input.

Wouldn't make a blind bit of difference unless the original plug was needing replaced anyway.

gn2 wrote:Wouldn't make a blind bit of difference unless the original plug was needing replaced anyway.

True

I just used the appropriate sized NGK plug at the 5000 mile interval that I got form powersportsplus.com. My PCX would run the same, nothing more, nothing less.

i agree with previous posters. the difference you saw in your old scoot was due to needing a new plug or even just a plug cleaning. i just buy the cheaper normal plugs and clean or replace them as needed.

I've heard that orientation of the spark plug can make a slight (1-2mpg) difference in fuel economy, because of the way the spark ignites and the subsequent combustion occurs in the cylinder.

From what I understand, Iridium plugs last longer than stock copper ones, but they also don't provide quite as strong a spark. That would indicate to me less combustion, which might explain why your Metro felt smoother. I'm by no means a mechanical engineer though, so take that as you will.

I installed the iridium plug for the PCX. I bought the last 2 off amazon last year. Good luck finding one. I did not notice anything different. I do plan on runing it 2-4 times longer than stock.

There wont really be any difference. Id like to run a brisk racing plug, but they dont make one that cross references to it.

Thanks all. Appreciate the discussion. On my Metro, the plug was cleaned and gapped recently, but I was still getting a rough idle at cold start and not terribly smooth acceleration. Perhaps my older plug was just worn down?

Either way, I may get one of them and see if anything changes on my PCX. For $10, how bad could it be? I'll let you know what I see.

Cool, I look forward to hearing back about it. $10 is less than the cost of lunch here, so if it makes even a minor difference, it's probably worth it for my next plug.

Iridium spark plugs make a huge difference,they did in my car

gn2 wrote:Wouldn't make a blind bit of difference unless the original plug was needing replaced anyway.

They only make a difference in a PCX if the original is due for replacement.
In comparison with a brand new standard plug there is absolutely no discernible difference.

ericpcx wrote:Iridium spark plugs make a huge difference,they did in my car

gn2 wrote:Wouldn't make a blind bit of difference unless the original plug was needing replaced anyway.

It'll have been more that they were new plugs than that they were "iridium"

Just looking into what kind of plug my Forza has...and came across this thread.
Always interesting to hear guys talk oils (synth. or dino?), gas (reg. or prem.) and lately, spark plugs (reg, copper, iridium)
Here's my experience on my 163cc Kymco, A/C, EFI.
The new scoot had a new NGK stock plug. After 400 miles I changed it for the proper NGK Iridium plug (after an email from NGK to confirm) and:
1) my idle speed increased slightly (noticeable on the center stand and when rolling off the throttle approaching a stop)
2) but more importantly, the scooter idled more smoothly at stop lights...with none of that passing stumble you don't want to hear when sitting in heavy traffic at a light.

These things last a zillion miles - but who cares since it costs $7.50 and are easy to find at auto parts stores.
They are purported to have a hotter, smaller spark off their tiny tip.
Whatever, was the best $7.50 improvement to my scoot.

Denso makes one, too. But I did not like the color of the Denso after 500 miles and went back to the NGK Iridium.
(did I test with a newly purchased, stock OEM NGK 1000's of miles down the road? Yep, the idle was better and more reassuring with the Iridium, so I put it back in, and closed my book on spark plug trials)
Fish

I think I know the answer to this but here goes. When I had my Burgman I purchased a new spark plug for future use. Then I traded in my Burgman and forgot about the spark plug. Today I found it by accident and wondered if it would work in my pcx. I am betting that it won't. It is a NGK CR7E. The book says to use a NGK CPR7EA-9. I have no idea what the difference is. Whatever it is I am betting that I will be giving the spark plug away to a new home.

The spark plugs are different. One has a protruding electrode and the other doesn't.
For the price of the plug I would get the correct one.

I think the biggest issue, if you drive near beaches or salt/corrosion areas, is to switch out the plug every year or two, so it doesn't gall or seize in the head. Believe it or not -- if you over-torque or leave it in there too long the threads will sieze on the plug, leaving metal shavings inside the cylinder or coming out with the plug -- neither scenario is good. budget $100 for a new head or remove and tap/h-coil spark plug hole to fix is a time and $ consuming task. The labor to swap the head is going to be well into the 3 digit range. I put a small amount of anti-seize on my plug (tip to base) so I'm not playing this game ever again. It happened when buying a used scooter 3 years old at only about 2200 miles, it was never changed.... and the guy had it on the gulf of mexico a few months a year and he towed it open, behind his RV. I imagine a ton of rain with a bit of salt was constantly on that head. It was fixed, but what a pain. that's why I bought new on this round, and I'm doing the maintenance so I know it's actually done. Just changed mine last night on the PCX. at 1300 miles the factory oem one was not so crisp looking. Consider that salt air goes up the tailpipe into the cylinder or packs the air filter and passes into the engine a bit -- if it's not shiny then it's probably not working at 100% efficiency from carbon or slight corrosion. OEM NGK plug is only $3.19 at the new rielly-O auto parts store today (june 2017).

BTW - I saw on one OEM honda parts website the OEM o2 sensor is only $25. that also should be cleaned and/or changed. On my truck I removed my old ones at 110K and sprayed them out really good with electronic parts cleaner a few times and reinstalled. They were as good as new and really helped the truck as much as replacing them with new. A side topic -- Here is another oddity -- working on my sons VW passat with GDI high pressure fuel injection (direct into the head) -- now they build up MAJOR carbon on the intake side of the head (like 1/8" thick) because the injector cleaner no longer sprays onto the valves -- is only directly sprayed in the cylinder. I'll bet we scrapped 2 cups of carbon out of those intake ports at 92K miles. Lesson for scooters: always also use good fuel injector cleaner in the gas -- gas is crap quality anymore and you don't want carbon build up. This might also be the other side of VW reduced carbon emission program -- it stays trapped in your intake manifold now.

Good tips there, cold surfer; thanks!

When I worked for mechanical contractors, we had to watch steam fittings, and used a lot of never seize to protect threads on steam pipes for many years.

There are some manufacturers that recommend not using it, but I personally always paint clean threads on spark plugs (and many other things) with at least a trace of it. Don't overdo it. I have never in the past fifty years seen a problem with galling or seizing.