Cylinder: Cylinder head/foot gaskets - at SIP Scootershop

Thicker base and head gaskets, or spacers, are required for higher-set cylinders and cylinders with extended stroke.

Longer stroke

When using a long-stroke shaft, half the length of the extra stroke must be compensated by a head and/or foot gasket. If the stroke is compensated by a foot seal, the exhaust times will be longer and the overflow times will be significantly longer. If the outlet is also raised slightly by milling, the engine is optimised for higher speeds. Compensation by a head gasket extends the exhaust and overflow times only slightly, whereby the overflow time changes more than the exhaust time (=less advance). This is an optimisation for more torque at medium engine speeds.

Longer connecting rod

With a longer connecting rod, the stroke does not change, but the cylinder must still be raised by the difference in connecting rod lengths.

The base gaskets are available in thicknesses of 0.5-10.0 mm, the head gaskets are available in thicknesses of 0.5-2.0 mm. They are usually made of aluminium.

ConclusionLong-stroke shaft tuning with different spacer combinations is one of the performance enhancements of recent years. This is where the wheat is separated from the chaff.

SIP tip

Don't forget the right long-stroke shaft! Longer stud bolts are often needed with thick spacers.

Customers ask - SIP answers

"What is the point of setting cylinders higher or lower?"

By "raising" and "lowering" cylinders, you can specifically influence the overflow and exhaust timing of an engine - the special focus here is on the overflow timing. The usual way is to raise the cylinder by means of a metal foot gasket in order to lengthen the timing and make the engine more rev-happy and powerful. However, the foot gasket also changes the position of the top of the cylinder as well as the compression of the engine, which usually requires further work on the cylinder and/or cylinder head. Reworking the exhaust is also almost always necessary or desirable.