Replace Spark Plug Cap???
 

Over on ADVriders there is a post recommending replacement of the stock spark plug cap with an NGK cap to improve connection with the spark plug. This is a cheap swap, and having replaced spark plug caps on other bikes, I went ahead and did it.

I now think this is not such a good idea.

The stock RX3 spark plug cap is crimped onto the spark plug wire. You cannot simply unscrew it and replace it with a generic NGK replacement. You need to cut the wire. (It appears on the CSC parts diagram that the cap and wire come as a single unit.) Also, the OEM cap uses a simple direct metal connector between the wire and the plug. Unlike NGK caps, it is not a resistor design. Finally, the wire itself is not a copper core wire. It is more difficult to set the screw in the NGK cap. So while the NGK cap may offer a better connection with the spark plug, I think you end up with a weaker connection between the cap and the wire, and more resistance in the circuit that the OEM design.

If you decide to go this replacement route, I found NGK VB05F (NGK stock number 8032) was a duplicate for the size and angle of the OEM cap.

But if I had it to do over again, I would not go this route. If I suspected the OEM cap was loosing contact with the plug, I'd consider getting a new OEM cap and wire.

Hi NoVa,

I made the change to the 90 degree NGK...had no problem, rode 100 miles today.

Like you I was curious about the stock wire.....what kind of core is it? Kept looking for metal strands but could find none.

Do you know if the wire detaches from the coil or is molded on?

http://i42.photobucket.com/albums/e3...psuwsswcnr.jpg

Might have preferred the 45 degree cap, but this seems to be working OK.

jb

JB, it's quite possible the coil wire is a graphite embedded fabric conductor as is commonly used in the auto industry. It's used for suppression of EMF.

CSC shows the cable/wire separate from the coil. http://www.cscmotorcycles.com/RX3-El...ents-s/150.htm

Thanks Jay,

Think I will replace the wire as well.

jb

I see where you can now choose USPS shipping:yay: much cheaper than the ups.

I just checked the stock spark plug wire with my cheapo ohm meter. I get about 4000 ohms resistance in the wire. Which means if you just put an NGK resister spark plug cap on the end of the stock wire, you have roughly doubled the resistance in the circuit. Does this matter? I really don't know. jbfla and others report making the swap with no problems. FYI the wire fits into the coil using a simple screw post along with the rubber boot. Correction on June 6: The OEM wire has a crimped fitting that goes over the post in the coil; not sure how well this post would work as a "screw" into a bare spark plug wire.

Guess we will find out....;)

I don't know about Jay's guess of a graphite embedded thread for the ignition wire.

Should I be able to see the graphite?

I looks to me like just a piece of string with a thin wire coiled around it.

http://i42.photobucket.com/albums/e3...ps8cl26hi5.jpg


I purchased some real low tech ignition wire....stranded steel:

http://i42.photobucket.com/albums/e3...psxjiw586q.jpg

http://i42.photobucket.com/albums/e3...ps9xor28jy.jpg


After I removed the stock wire from the coil, I twisted the new wire on until it bottomed out....it seems like a solid connection.

Then did the same with the new NGK spark plug cap.

I've been riding for two days on and off pavement. There seems to be no difference in operation of the bike.

We will see how long it lasts.

jb

FYI, Here's a pic of a dissected older 1974 plug cap off a Honda MT125 that I just replaced. It ran fine when cold, then after riding and shutting off , trying to restart wasn't easy. It would start and run a few seconds , then die like the ignition switch was turned off. The screw on the LH side is what the coil wire screwed onto. Then there is a resister thingy that ohmed out at 5000 1kw so that part was good. Then the little spring brought the spark around the bend and touched the brass insert that went over the S'Plug. I believe the problem was the spring end wore on the brass piece so it wasn't making as good a contact as when new. You can see a crater worn where the spring contacted the brass insert for the S'Plug .Replaced it with a $5 NGK one and it works great with no more problems, "so now you know the rest of the story". rj


http://i248.photobucket.com/albums/g...pspykrfuox.jpg