Yamaha WR250FM Decompression system, Timing chain tensioner, Assembly and Installation Camshaft

CAMSHAFTS

ENG

Decompression system

1.Check:

• Decompression system

Checking steps:

•Check that the decompression mecha- nism cam 1 moves smoothly.

•Check that the decompression mechanism cam lever pin 2 projects from the camshaft.

Timing chain tensioner

1.Check:

•While pressing the tensioner rod lightly with fingers, use a thin screwdriver 1 and wind the tensioner rod up fully clock- wise.

•When releasing the screwdriver by press- ing lightly with fingers, make sure that the tensioner rod will come out smoothly.

•If not, replace the tensioner assembly.

ASSEMBLY AND INSTALLATION Camshaft

1.Install:

•Exhaust camshaft 1

•Intake camshaft 2

Installation steps:

•Turn the crankshaft counterclockwise with a wrench.

NOTE:

•Apply the molybdenum disulfide oil on the camshafts.

•Apply the engine oil on the decompression system.

•Squeezing the decompression lever allows the crankshaft to be turned easily.

•Align the T.D.C. mark a on the rotor with the align mark b on the crankcase cover when piston is at T.D.C. on compression stroke.

4 - 27