This handy filter uses a 35 mm intake.

2-3/4″ x 3-3/4″ foam filter & hose clamp included.
Our 35 mm foam air filter with an angled fitting for 50cc, 70cc, 90cc, 110cc ATVs and dirt bikes does a superlative job of keeping the dust & crud from getting sucked into your engine. This filter is lightweight, affordable, and easy to replace, and it features a 2-3/4″ x 3-3/4″ foam filter and hose clamp.
This universal dirt bike air filter (air cleaner) fits most sizes of mini ATVs & dirt bikes. This dirt bike part is compatible with engine sizes of 49cc, 50cc, 70cc, 90cc, 110cc, & 125cc/150cc. The key dimension is 35mm, which is the inside diameter of the rubber fitting that you place on your carburetor. If your dirt bike carburetor has a 35 mm air inlet, which most 50cc-150cc carburetors do, this air filter will fit your dirt bike. Just pop it on, tighten the hose clamp and your engine is breathing clean again.