Dear Mr. Know-It-All,
I just purchased an S3 head for my 2020 KTM 300XC and have a problem. I opened the kit, and I see the included head O-rings and crush washers, but I have one extra O-ring; it’s a smaller size. Where on earth does this O-ring go? I don’t want to install the head and have to take it back off.
Storm Zenobio
via [email protected]

Good call on not installing the head and leaving out the random O-ring. Since there are no instructions inside the kit, I can’t blame you for not knowing where it goes. Your inner dome separates from the outer shell, and you can press the two pieces apart with some force just using your hands. Once the inner dome and outer shell are split, you will see a groove around the spark-plug hole. This is where your pesky O-ring will end up going. Now you can snap the dome back into the outer shell and install the head leak-free.

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