Yamaha YF200 R1 Owner's Manual - page 21
YAMAHA YF200 R1
Page 22
Cylinder Head Prep & Assembly
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Cylinder Head Prep:
Match and blend intake and exhaust ports with the valve
bowls. Pay special attention to the intake
runner where it enters the bowl as it is
offset to promote swirl and needs to retain
the offset in order to maintain the swirl
characteristics. Next mount the intake
manifold to the head and blend the
junction. The outlet of the manifold has
been purposely left a little undersize so
that it can be increased to match the
head.
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Note:
the valve seats are finished at
the factory so care must be taken not to damage or nick them during the porting
operation. (You can mask them with duct tape) (Go to www.goodson.com or
www.ruffstuff.com for porting tools.)
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Valve Lapping and Seating:
The valves and seats are ground from the factory
and can be run as is without any problems or they can be lightly lapped with a fine
lapping compound. Either way is acceptable.
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Cylinder Head Assembly:
Thoroughly
clean the head to remove grinding dust
and lapping compound (if used). Be-
fore installing the rocker arm studs run
them down onto their threaded holes to
make sure they seat correctly against
the hex. If they do not seat on the hex
it will be necessary to run a 6X1.0 mm
tap into the hole to clean up the thread.
After this has been performed lay the
push rod guide plate on the head with
the guide tangs facing the combustion
chamber. Place a small amount of (blue) Loctite on the coarse threads and screw in
the rocker studs torque to 85 in/lbs. Install the appropriate 6mm studs on the intake
and exhaust flanges. Use (blue) Loctite and run the stud down until it lightly bottoms
and tighten it a ¼ turn more. Next, press the intake valve seal in place and install the
valve using the blue spring. Install the exhaust valve using the red spring. Be sure to
use a high-grade assembly lube on the valve stems. Now the head is ready for fitting