Top End Engine Rebuild Kit - 300cc - Sherco 2011 to 2022 (+ Scorpa 2015 to 2022)

Part Number
RKTS2011300
Grouped product items
Product Name Price Qty
S3 300 Piston Kit - GasGas Pro / Sherco / TRS / Beta / Scorpa - Size A
3 in stock
£158.95
S3 300 Piston Kit - GasGas Pro / Sherco / TRS / Beta / Scorpa - Size C
1 in stock
£158.95
S3 300 Piston Kit - GasGas Pro / Sherco / TRS / Beta / Scorpa - Size B
4 in stock
£158.95
Cylinder Gasket 250/290/300 - 0.5mm - Sherco 2011>2022, Scorpa 2015>2022
9 in stock
£9.43
Sherco Cylinder Gasket 250/290/300 Shim - 0.4mm
5 in stock
£8.80
Sherco Cylinder Gasket 250/290/300 Shim - 0.3mm
20 in stock
£4.08
Sherco Cylinder Gasket 250/290/300 Shim - 0.2mm
2 in stock
£3.12
Sherco Inner Cylinder Head O-Ring Large
96 in stock
£4.77
Sherco Outer Cylinder Head O-Ring Large
112 in stock
£4.98
31x2.5 Viton Cylinder Head Insert O-ring
45 in stock
£2.00
Cylinder Head Copper Washer - M6x12x1.5
750 in stock
£0.45
Cylinder Exhaust Gasket - Sherco 1999 On, Scorpa 2010 On
12 in stock
£4.55
Exhaust O-ring - Sherco 2014>2022, Scorpa 2015>2022
78 in stock
£3.30
Athena 18x22x22 Little End Bearing
9 in stock
£7.20
Aluminium Flat Seal Crush Washer - M5x9x1
261 in stock
£0.30

Top end rebuild kit including the piston, gaskets and O-rings

For the Sherco ST300 trials bikes from 2011 to 2022.
Plus the Scorpa Twenty SC300 from 2015 to 2022.

Please note the later bikes came with the 2 piece Oxia insert style head fitted these use the 31x2.5 Viton Cylinder Head Insert O-ring, if you have an earlier bike with the cast head this is not required, there is also a M5 sealing washer used on the bleed screw, again you can remove 1 of these if you have a cast head. 

Please select the piston letter size and base gasket size required to suit your bike, each bike is different, the base gasket do come stacked up to 3 high from the Factory.

Piston Sizes

LetterSizePart number
A 78.95mm 3218
B 78.96mm 3339
C 78.97mm


The factory recommended piston to cylinder tolerance for the 300 is 0.05mm, if you are considering putting the next size up piston in please be aware that your original piston will have worn down and any wear in the cylinder is unlikely to be uniform down the bore so please check the bore size all the way down the cylinder and from left to right as well as front to back, the factory measure the piston and cylinders at 24 degrees C. The piston is measured front to back and 19mm up from the bottom of the skirt, be aware that the pistons are manufacture tapered (larger at the bottom) and oval (larger front to back) to allow for unequal expansion of the piston in use.


18mm Gudgeon Pin by 56mm long
Centre of the gudgeon pin to the top edge of the piston 28.8mm
Overall height 66mm
Weight including rings, gudgeon pin and C-clips 280 grams

The base gaskets are available in different thicknesses to allow the correct squish clearance to be achieved. The standard gasket is 0.5mm thick and is commonly used with one of the thinner shim gasket, some bikes even come from the factory with 3 gaskets.

We recommend you set your squish (the gap between the top edge of the piston and the cylinder head) to around 1.30mm.

More Information
Manufacturer Sherco
Year 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022
Model 300
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