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Message started by stewmills on 07/09/14 at 10:49:09

Title: Sparky Plug
Post by stewmills on 07/09/14 at 10:49:09

So I reviewed the tech section and see the brands of plugs noted as valid for our bikes but I'm not seeing exact numbers, etc. leading me to the specific size (e.g. hotness :o) plug.

I have a stock 2008 that was jetted one size up along with the white spacer mod just to fix the sluggish factory settings. When I did a previous oil change the tech at the dealership selling me some stuff gave me a plug that he said would 'run a little hotter' which at that time I thought meant make the bike run hot though now I understand it meant that it would help with the performance.

Long story short, I don't remember what the plug size is that he gave me without taking the tank off and I am wondering with my oil change this weekend if I should put in a new plug and whether I should go with the 'hotter' plug that's in there now or factory recommended plug.

For the spark plug novices (me), what is the best performing plug(s) for our bikes that are pretty much stock aside from the rejet and spacer mod? Flavor and part#/model# if possible please.

Thanks as always. This forum is always spot on with tips and tricks for novices such as myself.

Title: Re: Sparky Plug
Post by oldNslow on 07/09/14 at 11:15:23

standard heat range -NGK DP8EA-9 or ND X24EP-U9

hotter - NGK DP7EA-9 or ND X22EP -U9

The only reason for a hotter plug is so the plug will keep itself clean if the bike is jetted a little rich. There is no performance benefit. If the center insulator on the standerd heat range plug is a light tan color it's fine.

Suzuki recommends changing the plug every 7500 miles. If your bike is running OK there is no reason to replace it oftener than that. I'm pretty sure that a lot of folks run them longer than that.

Title: Re: Sparky Plug
Post by Dave on 07/09/14 at 12:27:53

About the only reason that could justify changing the heat range of the stock spark plug....is a worn out engine that is buring oil and fouling the spark plug. Or maybe.....if you are a Shriner and riding the bike in a lot of parades at 2 mph!

If your jetting is affecting your plug....your jetting is wrong.

Title: Re: Sparky Plug
Post by stewmills on 07/09/14 at 12:34:56

Thanks oldNslow and Dave. I'll take a gander at it while I am in there working on things alongside the oil change (gotta take the tank off to do the speedo rattle mod using the fuel line...and maybe the front seat raise mod) and make sure nothing looks questionable.

Overall the bike runs good and I have no suspicion that the jetting affected anything, just making sure to 'splain the status of my bike to get the appropriate suggestions.

Thanks! :D

Title: Re: Sparky Plug
Post by stewmills on 07/09/14 at 19:32:29

Just as a follow-up, I pulled the plug and it's an NGK, DPR7EA-9. For whatever reason, mine as an "R" in the number...?

Here's a pic of what it looks like after about 2 years and 2000 miles.

Title: Re: Sparky Plug
Post by Kris01 on 07/09/14 at 20:34:43

Looks fairly new. I wouldn't replace it yet.

Title: Re: Sparky Plug
Post by oldNslow on 07/10/14 at 04:49:30

Like Kris01 said, that plug looks fine. When you do replace it I'd just put in the DP8EA-9 though. I don't think you really need the hotter plug. The "R" in the # just means that it is a resistor plug. The resistor is supposed to keep the plug from interfering with electronic devices - ECUs, ABS computers, stuff like that. Not really necessary on an S40 but it won't hurt anything.

Title: Re: Sparky Plug
Post by stewmills on 07/10/14 at 06:42:44

Thanks folks! Much appreciated and glad to see/hear that it seems to be right where it needs to be.

I cleaned it off for good measure and put it back in. Will check it again at the next oil change.

Title: Re: Sparky Plug
Post by DavidOfMA on 07/10/14 at 21:28:22

FWIW, I changed the plug in my 2007 S40 at around 8,000 miles and it still looked almost new. Standard, except for the white spacer mod and the TEV spring mod.