If it's threaded the same and is not longer than your other plug where it could possibly hit the piston just run it.

There are many other brands of plugs than NGK. And most dealers are the worst place for accurate info.

I have an 05 CRF250R. Get the plug from Oreilly Auto Parts. They will have to order it but you should have it in a day. The 05 CRF250R went from a coil on the frame and a plug wire to a coil on plug setup. I only replace the plug in mine twice a year. Oreilly's will use the NGK stock #7791 to order it. I think it was about $24. I believe the newer CRF450R's also use this plug, but I'm not sure.

NGK Spark Plugs use the Letters and Numbers to identify the size and heat range of their plugs.
STANDARD TYPE FOR MOST MOTORCYCLES

NGK B8ES

A B C D J etc is the diameter of the hole such as 14mm or 12mm ALL Spark Plugs are metric threads.

2 - 11 The Number is the heat range, ability for the plug to extract heat away from the combustion chamber.

Lower the number with NGK the hotter, higher the colder.

Third Letter if used, indicates the length of the threads. If none is standard based on diameter.

Last number in the standard NGK is the type of electrode.

http://www.ngksparkplugs.com/docs/tech/partnumberkey.pdf
NGK SPARK PLUG CHART

When I started riding motorcycles in 1964 a spark plug cost 25 cents. I can't imagine any spark plug being worth more than a $1.50. And brand new bikes up to the 1973 Kawasaki 750 never cost more than $900 cash. But that is another story.

I am told that some will last longer in mileage, but I would think that would be for automotive use where it has become very difficult to reach the spark plugs to change them. A siingle cylinder motorcycle typically has ease of access to the spark plug.

I run standard B8ES NGK plugs with the black print in my 4 cylinder truck. Cost around $1.25 each at OReilly Auto Parts.

Never thought I would live to see the day when gasoline is $4.00 a gallon and a spark plug is $32.95!

When I started gasoline was 16 cents per gallon.

Of course when I was a kid I could buy 48 bottles of Coca Cola for the same price as one bottle of Coca Cola today.

Working at minimum wage when I was 14 I only had to work two days to buy 15,000 miles in gas for my Honda 90 and Four Weeks at minimum wage to buy 15,000 miles in gas for a 15 miles per gallon car. Today one would need to work 20 weeks to earn enough to purchase 15,000 miles at the current minimum wage.

Then minimum wage at $1.25 and a spark plug was 25 cents, gallon of gas 16 cents.
Now minimum wage at $6.25 and a spark plug at $32.95 gallon of gas $3.80

Something is way wrong in this country today.

I don't even recall there being a minimum wage back when I was a kid (60s/70s) in several of my first part time jobs / summer jobs ... and no one had ever heard of child labor laws with minimum age requirements... at least not in the small town I was raised.

I started working when I was around 10 around 1961 for my family. Got paid $1.15 per hour then, I remember my time clock cards and my pay check stubs. I would un-package merchandise and use a lable gun to place price tags on items that were sold in stores we sold wholesale merchandise to. We provided the merchandise on consignment in exchange for shelf space in the merchants stores. We also owned two large discount department stores and were partners with three others in two states.

In the summer of 1964, when I was 13, the minimum wage was $1.25 per hour, and you took home $40 for a 40 hour work week. There was no Workers Compensation Insurance then, it only was required after 1978. During summer break from schook, I collected shopping carts off the parking lot of my families discount department store. Kept the soda machines stocked up at the two entrances, swept the floors in the front and monitored the two restrooms and kept the trash cans and cig butt cans emptied, and also played the pre-recorded specials over the PA system. I earned $40 playing drums in my rock-n-roll band, we all got a big tip one night when we played for our friend who's dad owned a big oil company in town. It was $100! That was major money then.

http://www.easternct.edu/personal/faculty/pocock/minwage.htm

My friend that has worked in Kuwait for 15 years informs me that gasoline in Iran is around 6 cents per gallon today. That is because the wages there are very low and not too many people have jobs that pay much. Therefore the gasoline prices have remained low so they don't have to face the inflation that would cost them more for labor, housing and food as it has done here. Gasoline in Kuwait is still under a $1.00 per gallon today according to my friend who lives there. I read where diesel is $2.30 just across the Texas border in Mexico.

Wonder what an NGK spark plug sells for in Mexico?

Guess because we are now a credit card / debt conditioned society the global market has defined us as being able to afford $5.00 diesel, just ask for an increase on your limit on your gas credit card.