The older low compression 90cc heads have more of a dome/cone shape in the combustion chamber and the High compression head is more of a flat shape
You want the spark plug to fit to slightly protrude into the chamber not be up inside the threads of the head or out too far past the threaded area.
These parts may also fit the following racing mini quads 2 stroke 50cc Apex 50cc Artic Cat Polaris 50cc Eton 50cc Kasea 50cc ATV Can Am 2 stroke 50cc ATV, Kymco 50cc atvs, Standard Motors and Borosa plus most minarelli Horizontal scooter engines. The parts can also be used to upgrade Racing Scooters for the following Yamaha scooters as the Yamaha jog, Yamaha Zuma , Kymco scooters only 2 stroke two Eton two-stroke scooters, Kasea scooters and standard motor 50cc scooters. You must check fitment before ordering to ensure the parts will work on your 50cc scooter or ATV.
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Vendor: DRR USA