his is a Carburetor Main Jet (M4 x .7, length 7.2mm) for the GY6 50cc, 4-Stroke engine. These come in various sizes depending on your application. #74 is standard replacement with stock air box. , #80, and the #84 require a Performance Air Filter system and the #86 requires the Performance Air Filter and Performance Exhaust System to get top performance. Installing a Performance Air Filter and Performance Exhaust System will give you the edge you're looking for.

Mechanics Note: If you increase the size of your stock carb jet you will want to improve your air flow both in and out of the engine. For smaller upgrades replace the stock air filter with a Performance Air Filter for this engine. If you upgrade beyond small adjustments you will want to install a Performance Exhaust System to handle the increased combustion and minimize back flow issues.

Altitude can play an issue in scooter performance. When you are dealing with elevation you will want to rejet to prevent your engine from siezing and requiring a rebuild. You will loose about 3% in power for every 1000' in elevation. At 4000' feet you will have lost about 12% of your power output. You will want to go down one (1) jet size for every 1750' to 2000' you go up in elevation. When the air is colder it requires bigger jets because cold air is more dense. If it is 50 degrees colder you would increase your jet size at least one step up. If you don't, your engine may sieze on you.