Correct spark plugs

[Ronk]

My son has an XB & I have an MT5 - both have CPI exhausts & High Flow Air Cleaners - we are running NGKR CR7HS Plugs - plugs are burning light brown but motors were stalling at idle last time to pits - both motors are making good power - are these the correct plugs ??

 

[csp1971]

Have you adjusted the idle screw at all?

I've been using NGK CMR7H (3066).

Here is a good spark plug chart that gives you the meaning of the numbers (in case you care, I was interested, so I looked it up )

http://www.ngksparkplugs.com/docs/tech/partnumberkey.pdf

Looks like the only differences between what you are using and what I've been using are the M and S. Compact (M) probably doesn't matter. I'm not certain what the differences are in a standard electrode.

C: 10mm thread diameter

R: Resistor Type

7: Heat rating number (2 Hot ---- 11 cold)

H: 12.7mm thread reach

S: Standard 2.5mm center electrode

C: 10mm thread diameter

M: Compact Type

R: Resistor Type

7: Heat rating number (2 Hot ---- 11 cold)

H: 12.7mm thread reach

 

[Deluge]

From NGK:

Q: When should I use a resistor spark plug?

A: NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.

NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.

They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.

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Anyway, if you need a spark plug and you have a Lowes nearby, stop by and look around their outdoor power equipment section. The last time I was there they had Champion RZ7C's for about 5 bucks.

 

[Ronk]

Thanks for the spark plug info -I never knew what the numbers actually meant - very interesting - my son has adjusted his idle screw but I have not Thanks !!!!

 

[foxys]

I've found cmr7h's at both Checker (or Shucks, depending on where you live) and O'Reillys, as well as Autozone. Most places are 3 or 4 bucks a plug.

 

[Keith81]

I run the NGK CMR7H in my 26cc and 30cc engines (XT and MT)

 

[REVOlutionary Rampage]

NGK CMR7H are the way to go