Posts
768
Joined
12/6/2010
Location
Aarhus
DK
Edited Date/Time
5/8/2024 12:06am
I recently had a sparkplug failure that ruined the cylinder head on my YZ 250 from 22. I’m able to get a used head from a 21 pretty cheap. Are they the same? The 22 head says OG1, the 21 OG2.
Same part. You're just the 2nd OG now instead of the #1 OG.
When you say spark plug failure, do you mean the electrode fell off and marked the cylinder head?
If so it’s likely due to detonation, meaning there may be other issues that need addressing, e.g. fuel quality, too lean, timing, too tight squish clearance etc.
As @40acres said they are the same part, identical part numbers 5MW-11111-02-00.
As @CPR said, why did it fail, if you replace the head, without fixing the cause, you will have another failure.
I’ve noticed on a lot of Facebook pages there has been a recent problem with NGK plugs. The electrode tip breaks off. Some plugs within just a few hours
The Shop
Check around the outside edges of the combustion chamber for pitting on your old head.
If a YZ250 is detonating, the first place you'll see signs is at the outer edge of the squish band.
Exact same part since 2011 I believe...
Could be Chinese counterfeit plugs. There are lots of them out there.
That's what I was thinking. Ran into some knockoff automotive NGK plugs.
Where did you see these? I actually don't purchase them online, I usually purchase plugs from my local dealer or have found O'Reilly to have a very nice selection of NGK at good prices.
This was several years ago. A relative bought them online when they couldn't source them locally. Some of the printing on the box looked a bit "off" and after doing some detective work they were also missing some telltale characteristics on the plugs themselves. Decided it wasn't worth the risk and replaced them. I also use my local O'Reilly for the same reasons you stated.
Had a similar experience replacing an AF sensor. Got what was supposed to be OE replacement and the car accelerated with a noticeably "stagey" feel - like the butterfly would open in distinct increments instead of a smooth, linear response. Replaced that sensor with one bought locally and the problem went away. Swapped them once more to verify the condition was related to the part and got the same results.
Sadly, it's hard to know what's genuine and what's not nowadays.
https://www.ngkntk.com/newsroom/blog/emea/fake-or-not/
R7376 ngk is your friend here. Resists deto tip failure much better.
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