No more resistor spark plugs for me.

alchemysa · 11-22-2013, 07:47 AM

I've been using resistor plugs in my bikes and boat as recommended but I've had it with them. I'm convinced they don't last and they perform badly.

Heres the latest couple of examples that finally settled the issue for me.

I have a Suzuki 2 cylinder 40p outboard motor with electronic ignition. Late last season I fitted brand new NGK resistor plugs. These were labelled on the packaging as recommended for my specific engine. As soon as I fitted them I was disappointed with the performance but I only ran the boat once then stored it. This year I launched the boat again and on its first run it felt like it was running on one cylinder. On the second run it felt like it was on half a cylinder. Fortunately I still had the old 'non resistor' plugs so I put them back in, first one plug, then the other, with a run inbetween. The progressive improvement as each plug was added was profound. The engine is now running beautifully again.

Example 2. Today I went to start my chinese Skyteam dirt bike but it wouldn't fire. The resistor plug was virtually brand new but it had no spark. With an old non resistor plug fitted it started and ran perfectly.

I've come to the conclusion that resistor plugs are like other anti-pollution crap on an engine; good for the environment perhaps, but lousy for performance, reliability and fuel efficiency.

As far as I can tell resistor plugs are good for reducing radio interference only. That's not something I'm concerned about on a dirt bike or on a boat that has no sophisticated engine management.

I've Googled this topic a bit and the fear that non resistor plugs may damage electronic ignition doesn't really seem to have much reliable evidence to support it.

Any thoughts?

Weldangrind · 11-22-2013, 10:31 AM

A resistor of some type is wise for the CDI, but most plug wires already have an internal resistor. On a typical China bike, you can peel back the boot where the coil meets the coil wire, and unscrew the wire from the coil. Once you have, you can measure the resistance between the exposed wire and the plug cap. If there isn't any, run a resistor plug.

festivagt · 12-11-2013, 12:55 PM

I find most issues with spark plugs are due to HEAT RANGE and not plug type. Resistor plugs are basically required for the ignition system to maintain longevity and not fry themselves. I cooked a VERY nice and expensive MSD ignition system on my car by not using resistor plugs and carbon cored wires. Most engines - especially 2 stroke outboards - are very tempermental with plugs. Running too cool a heat range with a little too much oil mix in the gas and you will get fouled plugs or bad burn. Just by stepping up the heat range two you fix that problem and the motor runs good. Check the numbers on your old plugs in the outboard and see what they are. Probably not the stock heat range. Chinese bikes/motors in general are a hit or miss as to the repeatability of using the same heat range of plug and same jets in their carburators motor to motor. They get em close tho. I haven't found anything new out of the box from china that didn't need the carb rejetted. Your older plugs were probably the correct heat range for your motor. Alternatively - You can get bad plugs right out of the box especially if they have been dropped. It doesn't take much to crack the porcelain.

11-22-2013, 07:47 AM	#1
alchemysa Join Date: Aug 2013 Location: South Australia Posts: 45	No more resistor spark plugs for me. I've been using resistor plugs in my bikes and boat as recommended but I've had it with them. I'm convinced they don't last and they perform badly. Heres the latest couple of examples that finally settled the issue for me. I have a Suzuki 2 cylinder 40p outboard motor with electronic ignition. Late last season I fitted brand new NGK resistor plugs. These were labelled on the packaging as recommended for my specific engine. As soon as I fitted them I was disappointed with the performance but I only ran the boat once then stored it. This year I launched the boat again and on its first run it felt like it was running on one cylinder. On the second run it felt like it was on half a cylinder. Fortunately I still had the old 'non resistor' plugs so I put them back in, first one plug, then the other, with a run inbetween. The progressive improvement as each plug was added was profound. The engine is now running beautifully again. Example 2. Today I went to start my chinese Skyteam dirt bike but it wouldn't fire. The resistor plug was virtually brand new but it had no spark. With an old non resistor plug fitted it started and ran perfectly. I've come to the conclusion that resistor plugs are like other anti-pollution crap on an engine; good for the environment perhaps, but lousy for performance, reliability and fuel efficiency. As far as I can tell resistor plugs are good for reducing radio interference only. That's not something I'm concerned about on a dirt bike or on a boat that has no sophisticated engine management. I've Googled this topic a bit and the fear that non resistor plugs may damage electronic ignition doesn't really seem to have much reliable evidence to support it. Any thoughts? __________________ TIME IS RUTHLESS. Skyteam GT200. Honda '84 CT125 Ag bike.
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11-22-2013, 10:31 AM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	A resistor of some type is wise for the CDI, but most plug wires already have an internal resistor. On a typical China bike, you can peel back the boot where the coil meets the coil wire, and unscrew the wire from the coil. Once you have, you can measure the resistance between the exposed wire and the plug cap. If there isn't any, run a resistor plug. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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12-11-2013, 12:55 PM	#3
festivagt Join Date: Dec 2013 Posts: 3	... I find most issues with spark plugs are due to HEAT RANGE and not plug type. Resistor plugs are basically required for the ignition system to maintain longevity and not fry themselves. I cooked a VERY nice and expensive MSD ignition system on my car by not using resistor plugs and carbon cored wires. Most engines - especially 2 stroke outboards - are very tempermental with plugs. Running too cool a heat range with a little too much oil mix in the gas and you will get fouled plugs or bad burn. Just by stepping up the heat range two you fix that problem and the motor runs good. Check the numbers on your old plugs in the outboard and see what they are. Probably not the stock heat range. Chinese bikes/motors in general are a hit or miss as to the repeatability of using the same heat range of plug and same jets in their carburators motor to motor. They get em close tho. I haven't found anything new out of the box from china that didn't need the carb rejetted. Your older plugs were probably the correct heat range for your motor. Alternatively - You can get bad plugs right out of the box especially if they have been dropped. It doesn't take much to crack the porcelain.
	0