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Discussion Starter #1
CBR250R uses NGK SIMR8A9 plug. Which is equivalent with Denso IU24.

Now, what if CBR250R is being use on tropical country, hot day, congested traffic. Should the bike use colder plug (i.e IU27/IU31) ? So the plug wouldn't release heat quite easily.

Any feedback ?
 

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I would say no - use the stock heat range.

The engine temp is controlled by the cooling system in that situation, so as long as it's not running overly hot you are fine. Use a good oil (synthetic if possible) and watch the level - that's important because it doesn't hold much.

Running a colder plug is typically required when the engine is running at high RPMs for an extended amount of time (racing) or is heavily modified.
 

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Discussion Starter #3
Running a colder plug is typically required when the engine is running at high RPMs for an extended amount of time (racing) or is heavily modified.
What if the owner likes to do wide open throttle very often ? Especially on hot sunny day.
 

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What if the owner likes to do wide open throttle very often ? Especially on hot sunny day.
Not a problem. Does your gauge show that you are running hot? A stock engine can run wide open for quite a while before it becomes an issue if everything is working properly.

Coolant mix, thermostat operation, and engine oil quality and level are more important to keep an engine safe in hot temps. Synthetic engine oils can run way into the red without breaking down, and are a cheap insurance policy if you are concerned.

You can pull the plug and "read" it to tell you if the heat range is correct. There are articles out there describing how. Basically you are looking at the markings on the ground electrode I believe.
 

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What if the owner likes to do wide open throttle very often ? Especially on hot sunny day.
Just this summer I was at a track day with 95f heat. Bike never have a problem. This is such a small engine with more than enough cooling. Maybe if you were turbo charged then you would be concerned.
 

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Thanks for the link. It is very useful.
 
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