Beta RR 4T - 250, Workshop Manual

Page: 101 / 196

Checking the piston
– Replace the piston if oil consumption is excessive or if the pi-
ston skirt is scored.
– If the piston is to be reused:
1.Check the wear of the piston sliding surface.
2.Check that the piston rings can move freely in their grooves.
Clean the grooves with an old piston ring or with emery paper
(400 grain).
3.Check the piston ring wear and gaps (see below).
4.When installed, the piston pin should float in its hole. Replace
the piston pin if it shows signs of colour alteration or sliding.
Checking the piston rings and their gaps
– Insert the piston ring in the cylinder and align it with the piston
(approx. 10 mm under the upper edge of the cylinder).
– Using a thickness gauge, measure ring gap A .
Compression ring: max. 0.80 mm
Scraper ring: max. 1.00 mm
If the measurements exceeds the above values, check the wear
of the cylinder and piston. If wear is within the allowable limits,
replace the piston ring.
Checking the oil pumps for wear
– Insert the inner and outer rotors into the crankcase so that the
marks are positioned next to each other.
– Using thickness gauge B , perform the following wear measu-
rements:
Outer rotor – oil pump casing: max. 0.20 mm
Outer rotor – inner rotor: max. 0.20 mm
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6 - Motore
Release 01 Date 09/2007
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