Vespa PX Cosa GTR TS Sprint BGM Pro 177/187cc Piston Kit 63mm - A

Vespa PX Cosa GTR TS Sprint BGM Pro 177/187cc Piston Kit 63mm - A

The pistons of the BGM177 cylinder are manufactured by the renowned Italian piston manufacturer METEOR. The piston has a high silicon content. Therefore it has a lower thermal expansion, is more wear resistant and thermally very stable.

PISTON RINGS
Two 1mm thick piston rings, also made in Italy, minimize friction and thus increase power and speed stability. They are also identical in construction to the piston rings used by Parmakit and Polini.

CATEGORY
The pistons are available in categories A-D. The categories mean an increase in piston diameter of 1/100mm per ascending letter.
The category letter can be read on the piston crown. The cylinder also has a marking with a letter on its underside. Both should have the same category letter. If the cylinder already has a high mileage, a piston of the next higher category can also be used if necessary (e.g. B-piston in A-cylinder).

INPUT COATING
The pistons have a running-in coating of molybdenum disulphide. This coating is removed relatively quickly during operation. It only serves to perfectly align the piston with the cylinder bore. Please note that the coating itself is approx. 2/100mm is applied by the coating itself:

PISTON RUNNING PLAY
The piston running clearance should be between 5-6/100mm. This value refers to a piston without coating. The cylinder (with coated piston) therefore has a narrower running clearance (approx. 3-4/100mm) at the beginning of the delivery (with coated piston).