and Adjust Valves on a Honda CRF250
all know how important valve maintenance is on the
water-cooled Honda CRF's. Proper valve maintenance
includes checking clearance and adjusting the valves
as necessary. As frequently as this needs to be done,
paying a mechanic to do this for you can get expensive
fast. This "How-To" written by CRF's Only
member "Heckler" will show you step-by-step
how to check and adjust (shim) your valves on a Honda
CRF250X. This process is very similar to other CRF
1. First remove the seat by removing the two
bolts on the rear sides of the seat and slide it back.
2. Next remove the rubber strap holding the rear of
the tank down.
Using an 8mm socket remove the bolt holding the top
of the tank to the frame.
4. Remove the fuel line from the petcock. (Don’t
forget to turn the gas off...)
Remove the bolt holding the petcock.
6. Next remove the two lower shroud bolts on both
sides, leave the top ones in place.
Remove the tank and shrouds as a single unit and set
8. Clean the top of the valve cover off to remove
any dirt and debris.
Remove the spark plug cap by pulling up firmly, it
may take a good tug, move it off to the side.
10. Next remove the vent hose on the rear of the valve
cover and remove the two 10mm bolts.
Carefully remove the valve cover making sure you don’t
damage the gasket. (You can re-use this gasket if
you don’t damage it.) There is also a rubber
sealing ring on the spark plug tower, don’t
loose it or let it fall into the cam chain tower.
12. Next remove the cover on the lower right side
case, I believe it's an 8mm allen.
Turn the motor over clockwise until the punch mark
on the gear lines up with the arrow mark on the side
case. Check to be sure that the cam lobes are facing
to the rear of the bike, if they are pointing toward
the front keep going until they face back and the
punch mark aligns up with the mark on the case.
14. Check the cam gear to make sure the two marks
on the gear are level with the surface of the head.
Inset your feeler gauge under the intake lobes, it
should slide in with a slight drag. .005" is
spec for the intake valves; if it won’t fit
try the next size down etc. Write down your measurements
for both left and right valves.
Next do the Exhaust valves by sliding your feeler
under the rocker, spec for the exhaust valves are
.011" I use 12" long auto type feeler gauges
that are nice and flexible. Again, write down your
measurements for both left and right valves.
Make sure the rubber sealing ring is firmly seated
in the under side of the valve cover and set it back
Using a "QUALITY" torque wrench (1/4"
drive) Torque the valve cover bolts to 84 inch lbs
(or 7 ft. lbs.) Be very careful when tightening those
bolts, they thread directly into the cam bearing caps
and can only be replaced by buying the whole head
assembly, you can’t buy them separate. Replace
everything else in reverse order. Don’t forget
to replace the cover on the lower right case! IT"S
REALLY EASY!!!!! Takes about 15-20 minutes tops once
you get the hang of it.
Assuming you have recorded your measured clearance
(From valve check post) and installed shim size (You
will get the installed shim size later in this post)
use this spreadsheet
(Please right click and “save target as”)
to calculate your new shim size. All Honda shim sizes
and part numbers are listed at the bottom of the spreadsheet.
If you have a valve at zero clearance it will take
a few tries before you can get the correct values,
you must have some clearance for the spreadsheet to
Here to Download Valve Shim Calculator Spreadsheet
Remove the bolt on the cam chain tensioner.
3. I use a small flat blade screwdriver to release
the tension, turning it clockwise will release the
tension on the chain.
I use a small set of vise grips to hold the screwdriver
in place, the tension will hold the vice grips against
the side cover holding it in place. If you wish to
avoid this step or don’t have the vice grips
or screwdriver you can completely remove the chain
tensioner by removing the two bolts that attach it
to the head but you will need to release the tension
before re-installing it.
5. Remove the cam cap bolts in steps in a crisscross
pattern, loosen a little at a time to avoid warping
Notice I stuffed a rag in the cam tower opening; this
is in case something like the cam cap bearing retainer
clip or shims fall it won’t end up in your crank
Work the caps loose by moving them back and forth,
once you have them loose place a finger underneath
them to hold the bearing retainer clip in place so
they don’t fall out, if they do that’s
ok…. That’s why you have the rag in the
cam tower to catch them in case this happens. Do the
same for both sides.
This is what the bearing retainer clip looks like,
it fits in a groove on the cap and aligns in a groove
on the bearing.
Put a little grease in the groove to hold the clip
in place when you re-install the caps.
I use a perm marker and mark a spot on the chain and
gear as a reference when re-installing the chain.
11. Slide the bearing on the cam gear side to the
left, the cam will then drop down on the left side.
Next wire up the chain so it won’t drop into
the tower, if this happens its ok, it won’t
go too far, you will just need to fish it out of there
before you install the cam back.
Remove the chain then the cam from the head assy.
and place it aside.
The shim buckets are the round silver parts near the
rear of the head that were directly below the cam.
Lift the buckets up to expose the shims, you can also
use a magnet to remove them and often it will lift
the bucket and shim out together.
Usually even without the magnet the shim will stick
to the underside of the bucket. If not it will be
on the bottom of the valve that was under the bucket.
Remove the shim and it should have the size on it.
The size will read something like 195 which is 1.95mm.
If the writing has worn off you will need to use a
caliper or a micrometer to get the size, you will
need this to calculate your new shim size. Use the
spreadsheet at the beginning of this post to enter
your measured values. Once you have the correct shim
size ordered and in hand just place them where the
others were and replace the buckets. When replacing
the buckets put a little clean oil on them.
To get to the exhaust valve shims remove the small
cover on the right side of the head. If all you need
to adjust is the exhaust valves your in luck, you
don’t need to remove the cam or cam caps, you
will need to remove the cam cap bolts but that’s
Using a small screwdriver push the rocker shaft out
the hole in the side of the head you just removed
the cap from.
The rocker will now just lift out.
The shims are directly under the rocker, there are
no buckets over the exhaust valve shims. Remove the
shims with a magnet and replace them with your new
Replace the rocker, shim buckets, and cam in reverse
order of removal. Make sure your timing marks are
lined up (or use the permanent marker reference mark)
when you put the chain back on the cam gear.
22. Place the cam bearing caps back on. This may take
a bit to get them lined up as you need to be sure
the bearing retaining clip is properly lined up with
the groove in the bearing. The bearings slide around
so you may need to move them into position a few times
before you get it rite. You should be able to get
the caps all the way down flush with just your fingers,
“DO NOT FORCE THEM DOWN WITH THE BOLTS”
Next torque the cam cap bolts to 144 inch pounds or
12 foot pounds with a torque wrench. Again do this
in steps in a crisscross pattern. (Example: Tighten
them at 60 in lb then 90 in lb then 100 in lb then
144 in lb. etc.)Next remove the screwdriver from the
cam chain tensioner or replace it if you removed the
Using a "QUALITY" torque wrench (1/4"
drive is best) Torque the valve cover bolts to 84
inch lbs (or 7 ft. lbs.) Be very careful when tightening
those bolts, they thread directly into the cam bearing
caps and can only be replaced by buying the whole
head assembly, you can’t buy them separate.
Put everything back together in reverse order. Now
save yourself some money and do this yourself. It
really is very easy.
Only "How-To" By "Heckler" August