BRP-Rotax
REPAIR MANUAL
Instructions
See
Figure: Squish gap measurement.
1.
Rotate crankshaft by hand until the piston is approx. 5 mm below TDC.
2.
Right thickness of solder
2.0 mm (for 125 Mini, Junior and Senior MAX)
3.0 mm (for 125 Micro MAX only)
bend as shown in the Figure: “Squish gap measurement” and insert through the spark plug
thread into the combustion chamber until the solder is in contact with the cylinder wall.
The squeeze edge must always be measured in the direction of the axis of the piston pin. Di-
vergent measurements will show a wrong result!
3.
Rotate the starter gear assembly by hand over the TDC position.
NOTE
This will squeeze the solder between the piston and the combustion chamber
insert.
4.
Remove the solder from the combustion chamber and measure the thickness at the very
end (= “squish gap”) of the crushed end of the solder with a vernier calliper. Repeat this proc-
ess on the other side of the cylinder wall.
NOTE
A vernier calliper with an accuracy of min. 1/100 mm is required for this
measurement.
ATTENTION
Calculate the average of the sum of both measurements (on both cylinder wall sides).
The squish gap must be within the specified tolerance.
You find the latest valid regulations on:
http://www.rotax-kart.com/de/Max-Challenge/MAX-Challenge/Regulations.
NOTE
The squish gap can be adjusted using cylinder base gaskets. Cylinder base gas-
kets are available 0.2 mm (0.008 in.), 0.3 mm (0.01 in.), 0.4 mm (0.015 in.), 0.5
mm (0.02 in.) and 0.8 mm (0.03 in.) thick.
Engine model:
125 MAX –
EXAMPLE
A cylinder base gasket 0.5 mm thick has been installed. With this cylinder base gasket a
squish gap of 0.8 mm was measured. A cylinder base gasket 0.8 mm thick is required to
set the required value, e.g. 1.1 mm.
Of course a 0.5 mm and a 0.3 mm seal can be installed.
If it is necessary to install a cylinder base gasket with a different thickness, the cylinder
can be completely removed by unscrewing the four studs. Follow the instructions in sec-
tion “Installation of the cylinder”.
Keep in mind that the gasket will settle and reduce the squish over time.
Page 32
November 01 2021
Effectivity: 125 MAX evo, Junior MAX
evo, Mini MAX evo, Micro MAX evo
