Technical data

Section 04 ENGINE

Sub-Section 02 (TOP END)

040-02-14

Torque cylinder head screws to 12 N•m (9 lbf•ft)

as per following illustrated sequence. Repeat the

procedure, retightening all screws to 24 N•m (17

lbf•ft).

SQUISH AREA

Rotax rotary valve engines incorporate a combus-

tion chamber which feature a squish area. This

area is basically a “ledge” projecting beyond com-

bustion chamber area. In operation, as the piston

ascends and approaches the ledge, a rapid

squeezing action is applied to the air / fuel mixture

contained in the area immediately between the

piston dome and the ledge. This squishing action

forces the entrapped mixture rapidly into the com-

bustion chamber area, creating a greater mixture

turbulence. Additionally, the small volume and

large surface area of the squish band allow a bet-

ter cooling of the end gases to help prevent deto-

nation.

CAUTION : When reassembling an en-

gine, always measure squish gap to make

sure it is within the specified tolerance.

1. Squish gap

If the squish gap is increased, a loss in power will

occur, while too small a squish gap will lead to

detonation.

Squish Gap Measurement

The squish gap can be measured by inserting a

piece of resin core solder into the combustion

chamber.

– Insert solder in combustion chamber.

– Rotate the engine through Top Dead Center ;

remove the solder and measure the thickness

of the compressed solder.

NOTE : The solder should be inserted above

and in line with the wrist pin.

1. Solder

F01D46A

10 8 2 4 6 12

113 1 59 7

F01D5WA

F01D74A