Carb rebuild kit - what is this part?

[Brianc]

First post! What is this small disc for? This is from Scrambler’s rebuild kit of a 1980 xs.

[bikerphil]

It's a cap for the tower the idle mixture screw sits down in. They came capped from the factory to discourage any tampering (EPA) with the mixture screws.

[DiverRay]

You can use a dremel tool to cut a slice in the carb so without the cap you don't have water, oil, etc. collecting on top of the adjustment screw.

[Brianc]

Thank you both.

[Tim]

The earlier XVS13 (4 cyl yam cruisers) had plugs about that size you had to tap out and back in to replace the float needle seat like 1996 I'm thinking