 Ensure
the motor is cold.- Remove the fuel tank, fuel line, seat and side covers.
- Remove the four large valve inspection bolts with a socket the same
size as the rear axle nut.
- Remove the spark plug, place a screwdriver through the hole and rest
it on the top of the piston.
- Remove the timing inspection bolt on the LHS engine case.
- You want to adjust the valve clearance on the compression stroke,
that is when the intake valve has opened and air has been sucked in,
then the piston rises up compressing the air. Rotate the motor with
the kick starter so that the exhaust valve has just open, and then shut
and the intake valve is just about to open. You will feel with the screw
driver that the piston is at TDC and the ‘T’ mark will show through
the LHS inspection hole. This is not the correct TDC. Rotate the motor
a little further and you will notice the intake valve open up. Keep
rotating slowly and you will feel the piston rise again to another TDC.
This is the correct TDC to adjust the valve clearance from. If you look
through the LHS inspection hole now, you should see the letter ‘T’,
but it might not be perfectly lined up the groove in the case cause
the kick-starter spring won’t let it sit perfectly. I used a length
of string to hold the kick-starter at the perfect angle to line up the
two marks. There should be play in all the valve arms at this point.
There are several marks, so be sure you have the ‘T’ mark.. The key
things to remember are the T mark must be lined up, and there should
be some play in all 4 of the rocker arms.
- With your feeler gauge, (intake is 0.10mm and exhaust is 0.12mm or
0.003" and 0.004"), use a smaller feeler gauge just to see
how the clearances are at the moment on the intake valve. If you can’t
get it in between the bottom of the adjusting screw and the sub rocker
arm, the clearances are to tight and need adjusting. If the smaller
feeler gauge fits in and is quite loose, try the 0.10mm. If you can
get it in without struggling and there is just a light grab on the finger
it is perfect so don’t adjust it. If it to tight or loose, adjust it.
Check the exhaust clearance using the relevant gauge fingers.
- ADJUSTING THE VALVE CLEARANCE: using a 12mm ring spanner, loosen the
locking nut. Using a flat head screwdriver, screw the adjustment screw
out just enough for you to slide in the correct gauge finger. Screw
the adjustment screw back in so it is just applying a small amount of
pressure to the gauge finger. You should be able to still slide the
gauge finger around, but it should feel like it is grabbing a little.
Screw the locking nut down to secure the adjustment screw. When the
locking nut is tightened, it appears to raise the adjustment screw slightly
and reduce the amount of grabbing on the gauge finger, so experiment
and get it all tight but with the slight grab.
- Continue this for the remaining three valve clearances.
- Adjust the decompression system if required so it is not affecting
the rocker arm action and only touches the rocker arm when you pull
the decompression lever. The decompression system cable mount on the
cylinder head may cop a few hits and could be bent, so check this, as
it will affect the way the decompression system works. Then recheck
the clearances for peace of mind
- Replace the four large valve inspection bolts and the timing inspection
bolt on the LHS.
- Replace the tank, fuel line, side covers and the seat.
- Fire her up.
Credits: Article written and submitted by Craig Cullen and edited by 4Strokes.com.
Update 5-6-08: Clearance values changed from .010mm to 0.10mm, .012mm to 0.12mm, .005 to 0.05mm by David Closs and IVG. |
