dusty or sandy conditions the metering diaphragm can become contaminated
with dirt. The dirt can enter through the breather hole at the rear of
the carburettor. The hole allows the diaphragm to function properly
during carb activity and the resultant ambient pressure changes.
If the hole was to become blocked, or the diaphragm heavily contaminated
with dirt, the carb's performance would be affected.
Solution: The filter
is designed to keep the diaphragm free of dirt and reduce the need of
cleaning or replacement by protecting that opening - in a similar
fashion as the air filter protects the engine. The filter does not
require the carb to be removed for the install. This mod is based on an
original concept and part developed by Team Chase.
consists of cutting and grinding an aluminium channel, 15 x 10 x 1.5 or
1mm thick (1) to form the filter housing. A suitable
channel can be found in most good hardware stores. The 10mm width will
fit perfectly to meet the main body of the carb immediately below the
Cut a section of channel the same width of the carb body.
Depending on whether one is readily available, a spare carb, can be
useful in serving as a template, rather than having to remove an already
Remove the metal bulb holder (3) by removing the 4
small cross head screws and use as a template to ensure the required two
screw holes and curved section in the new filter housing are accurately
aligned. A 22mm diameter circle template may be useful to mark the
Drill the holes and grind down the curve as necessary
with your preferred tools.
Reduce one side of the channel (one of
the15mm sides) to meet the main body of the carb. Cut out a section of
the channel base to align with the cap headed manifold bolt which may
otherwise clash (4)
Using a HPI outer foam filter element or
similar, cut a small section that will fit neatly and squarely into the
newly made housing (6). Ensure the foam filter is not too compressed. If
desired, oil the filter in a similar manner to that used for oiling the