paragliding training center
by Had Robinson
Removing the cylinder head is straightforward. First remove the cooling shroud. Unfortunately, it has never been easy because the shroud sweeps around the cylinder exhaust port studs and you risk cracking the shroud if you try to force it over the studs. Why not remove the studs? That's not easy because, if the engine was assembled correctly, the studs were installed with red threadlock which means they won't come out without heat (a torch). To get around this annoying factory problem, take a pair of sharp wire cutters or shears and cut the wings of the shroud off just enough so that the shroud clears the studs. The effect on the cooling system in negligible.
Most paramotors use an "O" ring to seal the joint between the cylinder and the cylinder head. Whenever the cylinder head is removed, the "O" ring must be replaced.
DO NOT REUSE CYLINDER HEAD "O" RINGS!
This O ring is subjected to very high pressures (over 1,000 psi) and the slightest leak will affect engine performance and possibly warp the head. It is difficult to tell if the "O" ring is leaking because the hot gases that escape do not leave any traces. Glopping RTV on a used "O" ring looks like it will seal the joint but will not. This is because a used "O" ring has microscopic deformities caused by slight differences in the sealing surfaces. It is impossible to put the "O" ring back in the exact same position it had originally. RTV does not have the ability, by itself, to seal against 1,000+ psi pressures. Why suffer a loss of engine performance for a few $'s?
RTV is not needed when replacing a new "O" ring nor is it used by the factory.