this guide in full
you may have read anywhere JAWA and CZ motorcycle engines do
not require any form of gasket sealant on the cylinder head gaskets.
your head gasket is leaking you will see signs of oil/petrol weeping from
the joint. Sometimes you can simply tighten down the head but it is usually
better to remove the head and fit a new gasket. Always examine the old
gasket to see if it shows signs of “blowing”. This could be a burnt
area, a damaged gasket or just a dark streak of oiliness.
road bikes there have been two types of gasket. Older bikes had a fibre
asbestos type gasket and later models have aluminium gaskets. Neither gasket
type is reusable. Twin cylinder models have one gasket per cylinder and use
the same type gasket. The availability of asbestos gaskets is virtually nil
but it is safe to use the later aluminium gaskets as replacements.
gaskets form a seal by being crushed between the head and the cylinder. A
common problem is that riders say there is no gasket fitted. They are
normally wrong having failed to see the crushed gasket in the head.
is essential that all old gaskets are removed before new gaskets are used.
Even if you dig out one gasket just check there is no old gasket beneath it.
is always worth checking that both the cylinder head and the barrel top is
flat and this can be done simply by using a steel rule across the surfaces
or if you have a thick sheet of glass you can use that with great care.
Engineers use a flat steel plate to check trueness but the home mechanic is
seldom so lucky. If the barrel or head is only slightly warped you may be
able to true it up (make flat) by placing a sheet of emery paper on the
glass surface and rubbing the head in a circular motion on the emery on top
of the glass (to ensure it is flat). Major distortion requires either a new
head or the old head to be skimmed by a competent engineer. Generally it is
the head and not the barrel that distorts.
CZ recommend the use of a smear of grease simply to hold the new gasket in
place in the groove of the head prior to fitting.
models have 3 cylinder head nuts – one reason for head distortion - as it
is easy to tighten down the head unevenly.
CZ recommend that the piston is at top dead centre when you fit the head.
the head (with gasket in place) then tighten the head nuts evenly and gently
making sure the pressure remain equal by tightening opposites.
Final tightening really
requires a Torque wrench to achieve the required pressure. This is often 22
foot pounds (or metric equivalent 2.8 Kg's) but you should check the workshop
manual for your model for the actual specification and the settings on
your torque wrench. Again work round the nuts and try to tighten opposites
rather than doing one side and then the other.
tightened the heads do not usually require further attention but you may
wish to recheck the torque settings once the engine has run for a short
you have no torque wrench you are guessing so spend about £10.00 and do the
job right. Problems arise when under tightening the nuts as the gasket will
By Pete Edwards
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