The small chambers produce high compression ratios, but
they require a different piston than conventional 64cc or 72cc chamber
heads as a result of a combination of machining changes that reduce the
chamber volume.
The valves are closer to the deck in 49cc Iron
Eagle heads and their location relative to the cylinder bore centerline
is different than 64cc/72cc heads. Consequently the valve pockets in
many pistons are not in the right locations. However, Mahle has found
that its 21 degree flat top piston is a good fit for 49cc Dart heads –
the pocket locations and depth work very well for those using this
cylinder head.
Pistons from other manufacturers that offer 21
degree flat top styles should also work in this application, but it is
best to always check piston-to-valve clearance before final assembly.
–Courtesy of Dart Machinery
