Any colder plug then IFR9H11

I'm looking to get a colder plug for my X for summer riding here in BHC AZ. I went riding this afternoon it was 121 deg and after 30 minutes the engine started to tea kettle a bit and I had to let it cool down, not to mention I had to hide behind a hill in the shade. Anyone know of a cooler range plug? If not I will have to consult NGK, they really helped me to get my RM100 to stop killing OEM race plugs on the trail as the OEM race plugs were way too cold. But this is the opposite situation.

OK I found it NGK IFR9H11 IRIDIUM. Boy that was a short post.

I really dont think thats going to help.

Actually heat range changes in plugs are a very overlooked, misunderstood, and underestimated way of controlling cylinder head heat. This of course is only used during extreme changes in riding style and ambient temperature differences. But it wouldn't be the first time Iv been told that consulting the engineers at NGK is wrong. But they have sure solved this type of problem for me before.

Ahhh plug shmug.......

Dosent the temp. range of a plug refer to the temp. required for self cleaning??

Dosent the temp. range of a plug refer to the temp. required for self cleaning??

If your plug is burning too hot you can tell by looking at it....Then you can try a cooler burn....The opposite is also true.


A spark plug's heat range has no relationship to the actual voltage transferred through the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors: the length of the ceramic center insulator nose and its ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.

The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat or a race car, the spark plug tip temperature must remain between 450°C-850°C. If the tip temperature is lower than 450°C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C, the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing temperature is increased by 10° to 20°C.

The firing end appearance also depends ont he spark plug tip temperature. There are three basic diagnostic criteria for spark plugs: good, fouled, and overheated. The borderline between the fouling and optimum operating regions (450°C) is called the spark plug self-cleaning temperature. The temperature at this point is where the accumulated carbon and combustion deposits are burned off.

Bearing in mind that the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water journals. This means the plug has a higher internal temperature, and is said to be a hot plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity.

Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range can be necessary when the engine is modified for performance, subjected to heavy loads, or is run at high rpms for a significant period of time. The colder type removes heat more quickly, and will reduce the chance of pre-ignition/detonation and burn-out of the firing end. (Engine temperature can affect the spark plug's operating temperature, but not the spark plug's heat range).

**quoted from NGK***

Yup.....That's verbatim from the link I posted above. Good job, Krannie

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