2010 Stella Spark Plug inconsistencies - What the heck!

[Eel]

Just bought a used Stella and am working thru the maintenance. So I looked thru my owners manual and it gives an option of a champion RG4HC plug.

I finally get it in the mail today (this was near impossible to find in any local store in my area). I pulled out the old plug and the first thing that hit me is that though the sparkplugs are the same length the threads from the stock plug and my new champion are different lengths. The RG4HC sticks further into the motor as the thread portion is longer.

what the heck is going on here. Every where I go, (scooter west, scooter works, the stock plug I pull from the motor. Everyone has their own opinion on the replacement plug model number. On top of that NGK USA doesn't even show a compatible plug via their part finder.

Can anyone guide me in the right direction. Is the RG4HC going to fit or do I need to shim it to match the existing plug I have.

Also the RG4HC spark plug cap is different. My existing has a threaded screw and the new plug has a smooth cap. Any concerns here?

[stASH]

Don't know about the rest of your inquiry, but I think you can usually unscrew that smooth cap from the threaded post, so that end of the plug will be the same as what you have.

[Eel]

Don't know about the rest of your inquiry, but I think you can usually unscrew that smooth cap from the threaded post, so that end of the plug will be the same as what you have.

Cant on the RG4HC apparently its a Solid Stud. Kinda stupid that LML specs out something that doesn't work with the existing spark plug cap. I've ordered a CR8EHIX-9 as a replacement but its not ideal.

I did a LOT of research over the weekend and came up with a lot of minute concerns.

1) All the plugs specified in the manual are non resistor plugs. If you want an iridium plug (From NGK) from what I know it only comes with a resistor. So I'm stuck with a C8EH-9 (standard nickel electrode tip) or a resistor based iridium tip. I'm going to call NGK direct to see if they have another application in the factory specified heat range of 8

2) The added resistance of the iridium plug lowers the spark intensity but iridium has a better conductor than nickel. I'm not sure if its a wash or not. Again NGK can confirm this

3) The specified plugs sit much deeper than the stock bosch-mico that I pulled from the motor. Spun the motor around manually using the kickstarter and it didnt look like the deeper sparkplug hit the cylinder so might be ok. Still need to look into it after I've torqued it down.

4) I found a video on youtube that shows how to remove the connector terminal to get to the resistor (at least in champion plugs). I'm not sure if the NGK plugs have a resistor cap or a physical resistor inside. If no alternate spark plug options are provided by NGK, I may have to remove the terminal connector to remove the resistor (still only a theory) and replace with a solid copper core. This would allow for a zero or near zero resistance plug with the benefits of iridium longevity and spark performance.

We'll see what comes out of this. The ghetto solution is to buy a C8EH-9 and pop it in.

[Eel]

Well after having a conversation with NGK, they indicate that there are no plugs that substitute for an iridium style without a resistor. So essentially for this product a C8EH-9 is the only non resistor style that will be compatible with the unit.

I already have an order placed for the CR8EHIX-9 model so I will be tweaking it to see if I can dissssemble and convert it to a non resistor plug. Probably wont work per NGK.

[BuddyRaton]

I'm really trying to be nice but if you don't know to unscrew the cap so the ignition wire will fit I think you are in a bit over your head. I don't have a clue why you're worried about iridium or resistor plugs.


It's a freaking Stella with static timing and no radio. You're making this way more complicated than it needs to be.

[Eel]

I'm really trying to be nice but if you don't know to unscrew the cap so the ignition wire will fit I think you are in a bit over your head. I don't have a clue why you're worried about iridium or resistor plugs.


It's a freaking Stella with static timing and no radio. You're making this way more complicated than it needs to be.

Are you talking about the spark plug cap? If so I already mentioned that you can't unscrew it. It's a solid stud on the manual specified rg4hc. If there is something to unscrew on the wire. I probably missed that.

Oddly enough I'll admit that I'm having more trouble with this archaic tech as all my other vehicles have more modern ignition systems.

That said, it's hard to believe that only one type of plug is readily available in the USA for this model.

Can you list any others other than a C8eh-9? I can't find a bosch Mico if my life depended on it.

[fisher1]

I'm really trying to be nice but if you don't know to unscrew the cap so the ignition wire will fit I think you are in a bit over your head. I don't have a clue why you're worried about iridium or resistor plugs.


It's a freaking Stella with static timing and no radio. You're making this way more complicated than it needs to be.

Yep, +1 on that ...... here's a pic of the RG4HC plug with the cap unscrewed.... it's a European link, but clearly shows threads....

http://www.2wheelparts.de/Zuendkerze-RG4HC-Champion

If you can't unscrew the cap with a pair of pliers, just get a basic alternative plug that you can, no need for an expensive one.

[Eel]

I'm really trying to be nice but if you don't know to unscrew the cap so the ignition wire will fit I think you are in a bit over your head. I don't have a clue why you're worried about iridium or resistor plugs.


It's a freaking Stella with static timing and no radio. You're making this way more complicated than it needs to be.

Yep, +1 on that ...... here's a pic of the RG4HC plug with the cap unscrewed.... it's a European link, but clearly shows threads....

http://www.2wheelparts.de/Zuendkerze-RG4HC-Champion

If you can't unscrew the cap with a pair of pliers, just get a basic alternative plug that you can, no need for an expensive one.

You're making the same mistake i did. I blindly accepted that the owner's manual knew what it was talking about and ordered a plug. You're accepting a picture from a random site and accepting it as truth. Notice that it doesnt say RG4HC anywhere on the plug.

This is the real RG4HC:

http://houstonsuperbikes.com/i-8681209- ... -plug.html

You'll also notice the solid terminal at the top and in the spec

[BuddyRaton]

Take a pair of pliers, grab the "smooth" cap and unscrew it.

Champ RG4HC = NGK CR9EB

It's a scooter from India...not a Bugatti Veyron

There are no electronics on a Stella so forget about resistor.
It's a Stella...forget about iridium

I use resistor iridium in only one of my vehicles...06 Chevy SSR, 6 speed manual with a 6.0 L vette LS2, ported and polished throttle body with custom tune to 450 hp. It makes sense to use that kind of plug in that vehicle...not in a Stella

I'm close to calling Shenanigans!

[Robbie]

Well, not a four stroke answer but the plug discussion sort of applies.

I run a Iridium plug in my 2T Stella.
It is industry #9804......this is a RN8WY9B3 Champion.
The plug comes with the screw on terminal cinched on at four places that seem to be done with a punch press, locking the terminal on.
I took a small grinder to the pin marks and knocked them down to the point the thread was visible but not damaged.
Then, it unscrewed off with little resistance.

So, for the plug in question, you need to be able to look down on the terminal......there are two types.
If the top is closed, the terminal is part of the core pressed into the porcelan...that cannot be removed.
If the terminal has a hole in the top, it is a thread on.....it'll either be locked on as I described or just tightly screwed on.....and removeable.

Good luck,
Rob

[Eel]

Take a pair of pliers, grab the "smooth" cap and unscrew it.

Champ RG4HC = NGK CR9EB

I'm close to calling Shenanigans!

Fine, not a Bugatti Veryron I get it. But just to make it clear, the owner's manual is incorrect. See my pictures of a completely stripped RG4HC. I took it apart by heating the loctite using a 3 second burst of MAPP gas on the ceramic. Its useless to me anyways since there is no threaded top cap. I'll repeat that for the last time. Proof is in the pictures.

I've already ordered a replacement cheapo C8EH9 (which has a threaded stud cap).

The iridiums have a better spark efficiency and longer life. If I can modify a CR8EHIX-9 to work as a non resistor, its a cheap 1-2 dollars extra for an upgrade. I consider that a good return on investment.

Making a reliable , consistent spark is just as important as jetting other expensive mods like exhaust, etc

[Robbie]

Nuts!

I guess I didn't hit the Send button soon enouph.

Rob

[BuddyRaton]

Ok I'll admit I was wrong about the screw top. I've never seen one like that before. I will say that I prefer NGK. I'm more concerned with the plug heat.

If you want to use that plug just change the wire cap to a terminal clip.

[fisher1]

If the top is closed, the terminal is part of the core pressed into the porcelan...that cannot be removed.

Sheeezzz, what's the world coming to ??

[az_slynch]

NGK makes screw-on plug caps for either type of spark plug. Usually available from your local cycle supply for around five bucks.

http://www.ngksparkplugs.com/products/p ... p?mode=nml

[Eel]

NGK makes screw-on plug caps for either type of spark plug. Usually available from your local cycle supply for around five bucks.

http://www.ngksparkplugs.com/products/p ... p?mode=nml

Its definitely a way to get a plug installed but its definitely not cost effective. I did some digging and figured a few things out. Oddly enough I wouldn't have realized any of this if the Genuine stella owner's manual and service manual incorrectly specified the RG4HC Spark plug. Got me to start questioning things.

My goal was to find the best plug and the best bang for the buck all the while hoping that would be an iridium. Turns out the iridium is not a good choice unless you make significant changes to the resistance of the wire from the secondary coil to the spark plug .

Bottom line is a follows:

1) RG4HC - Champion - The wrong plug for the Stella 4T (I cant speak for anything but the USA model) and is incorrectly specified by the manufacturer unless you're willing to modify your plug cap to fit. Even if you did modify and install a new screw on plug cap as mentioned, the performance would still be below par compared to the NGK C8EH9. I measured a resistance across the RG4HC I dismantled (in picture above). The ceramic insulator by itself was 3000 Ohms. I didnt put it back together but I assume its the default 5000 Ohms.

2) UHR3CC - Bosch Mico - Specified in the manual and was actually the existing plug in my scooter. It will work but its not but the best option. I used a multimeter to measure the resistance between the plug cap and the electrode tip. Total resistance was 5000 Ohms. No difference than iridium models like the CR8EHIX9 but not better than the C8EH9.

3) C8EH9 - NGK- A standard plug but with almost no resistance between the spark cap and the electrode tip (approximately 1 ohm). Since the Stella is an old fashioned Magneto/CDI Ignition system, a lower resistance plug will result in a lesser load on the scooters ignition at worst and better performance at best.

Either way there's no reason to go with any other resistor style plug.

That said, the 5k resistor is already built into the spark suppressor cap. The service manual clearly states this on page 37 (at the bottom). So technically adding another 5k via the spark plug itself is redundant and inefficient.

Base resistance if you utilize a non-resistor plug is a little over 10000 ohm from the secondary coil to the spark plug electrode tip. By adding the 5000 ohm resistance to the system via a standard resistor plug you are decreasing the efficiency of your ignition system by between 30 - 33 percent. This value is based on the operational range of 25-32 KV as noted in the service manual. Simple Ohms law calculation.

Heat Ranges:

C8EH9 - Best Plug for Default Heat Range as noted in service manual

One step "Colder" - Technically it would be a C9EH9 but they seem to be hard to get. Most readily available option is the Denso Equivalent (also non resistor) U27FE9. Though I cant confirm whether this has a threaded cap. Someone might want to confirm before buying.

One step hotter would be a C7EH9 but again very limited availability. I couldn;t seem to find them online. Other option would be U22FE9 but again availability is very limited from what I can see.

So the only way I can get the equivalent performance out of an iridium is somehow reducing the resistance between the secondary coil output and the suppressor cap. Way too expensive for a scooter. Better to just spend 7 bucks and buy a C8EH9 spark plug.

[BuddyRaton]

WHY RED IS RED!

[chewy86b]

I've been trying to de-winterize my Stella (2013 4T), including replacing the spark plug. The NGK part finder says I should use NGK spark plug BR6ES, which had a .025 gap. However, my Stella owner's manual says to use NGK spark plug C8EH9 and that the gap should be 0.7-0.8mm. Also, I can't find C8EH9 at Canadian Tire.

Well I contacted NGK Canada, here is their response:

The recommended plug part number BR6ES (or stock # 7410) with a gap of 0.025”. BR6ES is a plug with a resistor whereas C8EH9 is not. C8EH9 is not a plug that we still carry. Lastly resistor plugs reduce ignition noise generated during sparking and is suggested for any vehicle that uses on-board computer systems. In this case you do not have complex on-board monitoring systems.

Regards,

Jason Williams

Technical Support

NGK Spark Plugs Canada Limited

Govern yourselves accordingly.

[Eel]

I've been trying to de-winterize my Stella (2013 4T), including replacing the spark plug. The NGK part finder says I should use NGK spark plug BR6ES, which had a .025 gap. However, my Stella owner's manual says to use NGK spark plug C8EH9 and that the gap should be 0.7-0.8mm. Also, I can't find C8EH9 at Canadian Tire.

Well I contacted NGK Canada, here is their response:

The recommended plug part number BR6ES (or stock # 7410) with a gap of 0.025”. BR6ES is a plug with a resistor whereas C8EH9 is not. C8EH9 is not a plug that we still carry. Lastly resistor plugs reduce ignition noise generated during sparking and is suggested for any vehicle that uses on-board computer systems. In this case you do not have complex on-board monitoring systems.

Regards,

Jason Williams

Technical Support

NGK Spark Plugs Canada Limited

Govern yourselves accordingly.

There is a fix for this. Based on my resistance measurements on the spark plug wire, the 5k resistance is built into the factory spark plug cap on the stella. You should be able to replace the resistor cap with an NGK "LZFH" style cap which has no built in resistor. If you do this, you could switch to an iridium CR8EHIX-9 and have the benefits of an iridium plug (long life, slightly better spark) and is readily available because its a standard plug for a lot of motorcycles.

I'll warn that the LZFH cap looks like it would fit based on the dimensions but I dont have one in my hand. YMMV

I was planning on doing this when my currently new C8EH9 needs future replacement.

[jamisfoes]

I am sorry for this elementary question and hijacking this thread. But, do you guys find the spark plug cap very loose on your stella? I have a 4T stella and the spark plug cap is so loose that sometimes it bouces off the spark plug and kills the engine. How should I remedy this? I have attached a picture of this (not an actual picture of what the Stella spark plug and cap...just for illustration). What can I do to make sure the spark plug cap is firmly attached to the spark plug "nipple"?

[Eel]

Actually, quite the opposite. I have trouble taking off the cap because its so tight.

Its attached with some sort of platic tab close to the plug. That seems to keep it pretty secure. Do you have this?

[chewy86b]

There is a fix for this. Based on my resistance measurements on the spark plug wire, the 5k resistance is built into the factory spark plug cap on the stella. You should be able to replace the resistor cap with an NGK "LZFH" style cap which has no built in resistor. If you do this, you could switch to an iridium CR8EHIX-9 and have the benefits of an iridium plug (long life, slightly better spark) and is readily available because its a standard plug for a lot of motorcycles.

I'll warn that the LZFH cap looks like it would fit based on the dimensions but I dont have one in my hand. YMMV

I was planning on doing this when my currently new C8EH9 needs future replacement.

Maybe I'll try this. I'm hoping a better/hotter spark plug might serve me better - mostly short rides, often in cooler weather.