How to inspect the valves on a Some of the information provided is basic 4-stroke
theory & design, and may apply to brands and models
KTM LC4... In three easy steps. other than KTM.
Written by Creeper Tools & Parts
This .pdf has been compiled and edited by dorkpunch. 1. A Motion Pro valve lash feeler gauge (.006" or
Please feel free to use and distribute this! My goal is 0.15mm) or reasonable facsimile.
to eventually have enough threads edited and format-
ted to make an actual service and repair manual for the 2. A set of metric Allen wrenches. You may find it nec-
LC4. If you would like to help, donations can be sent essary to "cut down" the short end of a few of your Al-
by paypal to: len wrenches to improve access to some fasteners. As
an alternative to cutting down Allan wrenches, if you
firstname.lastname@example.org. have a small ¼" ratcheting wrench and short metric
Allen insert bits... much like cut down Allens, they can
Having recently been asked, by absolute beginners as really come in handy on some of the limited clearance
well as mechanically inclined individuals, the process rocker cover bolts.
for inspecting/adjusting the valves on the LC4 engine;
I decided to write this guide. 3. A set of metric Allen sockets, preferably ¼" drive.
As an ex motorcycle technical writer and instruc-
tor, I take great satisfaction in someone performing a 4. A set of metric sockets, again, preferably ¼" drive.
complicated task, successfully and for the first time,
with nothing more than my written instructions... and 5. A ¼" drive ratchet and extension assortment.
maybe the occasional poke in the ribs.
I have written the steps to this process individually 6. Miscellaneous hand tools such as screwdrivers, pli-
several times, but have never put it all together in one ers, band-aids and so forth.
bite, until now.
7. I'm not going to list a torque wrench because most
This has been written for someone that has fair to folks don't own a 3/8" torque wrench, let alone the
good mechanical aptitude. more preferable but not so easy to find ¼" torque
If you're reading this with intent... and you're never wrench.
spun a wrench, you are a brave soul.
If you can take your bike apart and put it back togeth- 8. New rocker cover gaskets (yes, you can reuse the
er... and it still runs, you may find this mildly enter- old ones, once… if they are in real good condition)
taining, but by no means, new information.
9. Now would be a good time to consider replacing the
Part One. Getting there. spark plug if it has 5K miles or better on it.
We will use the 640 Adventure as our example, as it 10. Some Zip-ties in assorted sizes.
is the most complicated to "field strip" model of LC4,
and the one I happen to own. It is also the model that Why a ¼" drive set rather than the more common…
many of the folks reading this will own as well. 3/8" drive? The third rule of professional mechanics is
If you own an SXC, SMC or LC4E, the vast majority to use the smallest tool that will reasonably do the job.
of this information still applies, you simply have fewer Most fasteners on the LC4 engine are small and have
parts to remove and reinstall. Lucky you. relatively low torque values, there are no fasteners on
No doubt there are some variations from year to year, this job that require using the larger, bulkier, and with
but I don't believe they will be too much of an issue. greater potential for “excessive leverage” 3/8" drive
Older LC4s may have different valve lash specs than set.
more recent models… check your owners manual to
verify the specs for your bike. Proper Atmosphere That’s right… atmosphere.
(Two screws. one electrical connector)
What I mean, is a well-lit and relatively clean environ-
ment where you will not be distracted or disturbed. 5. Front rocker cover-to-frame vent hose. (Two screw
A separate clean space away from where you will be clamps)
working, to safely store the parts that you have re-
moved. 6. Rocker covers. Save the covers as the next to last
Nothing more entertaining than turning around sud- parts you remove or disconnect. (Three screws each,
denly, startled from your dog chasing your cat thru watch the washers)
your tools, and kicking your gas tank across the room
or, if the tank was full, breaking your big toe so badly 7. Spark plug. Save this as the last part you remove
you need morphine. or disconnect. If you have a compressor, blow out the
Drifty has suggested some laid back tunes like old plug recess thoroughly prior to pulling the plug.
blues or, if you’re like me, maybe some Emmylou
Harris. The idea being that you will have less a ten- 8. It is not necessary to remove the radiators. It does
dency to throw things or try to put a pipe wrench into make access a bit easier, but it is a trade off in time
your cylinder head. and hassle.
Disassembly You will need to partially remove and hold away the
following parts from the motorcycle.
I will not waste your time outlining the details of
things like tank or fairing removal, if you can’t do 1. Capacitor (one bolt)
these tasks, you may want to take your bike to a Deal-
ership or a trusted and mechanically inclined friend, 2. De-compressor cable (back off adjustment and dis-
with a copy of this guide. connect from lever... you can leave the cable attached
to the front cover or remove it... your choice)
Is your motorcycle clean? If not, after removing item
four, you may want to give the engine compartment a 3. You may need to snip a zip-tie or two along the way,
little bath. Don’t want big chunks of dried mud or little to move a harness or cable out of the way.
rocks falling in your motor, do you?
Is your motorcycle engine at room temperature? Don’t 4. See items 6 and 7 above.
perform this task 45 minutes after riding into the
garage. It takes several hours for an entire motorcycle 5. At this point, you should have more than adequate
engine to cool to room temperature. access to the four rockers and their adjusters. If not,
one of us has forgotten something and it might not be
You will need to remove the following parts from the you, because yes, I am doing this from memory.
Updated information as of 01-14-06: Now that you
1. Seat. (One bolt) have all the odds and ends out of the way, you may no-
tice that you have a bit of oil leaking from the rocker
2. Outer fairing (Six bolts. two turn signal electrical cover. If this is the case, and you want to fix the leak…
connectors) take a look at this.
3. Fuel tank. You do not have to remove your in- That’s it, on to part two.
ner dash, but it helps to get it out of the way for tank
removal. Use tie straps or elastic cord to tie the “ears” Part two. Finding TDCC
of the dash up to the handlebars. (One nut. three fuel
hoses. one vent hose, if any) A great deal has been written in this and other forums
about finding TDC-C. Some descriptions are quick
4. Cooling fan. Don’t force it; it comes out easy once and easy, written by and intended for people who have
the back tabs are popped from behind the radiator. a good grasp of how a 4-stroke engine works.
Other descriptions, written by some well-meaning Once you are near TDC (about 6 to 9mm from either
folks who undoubtedly think that the factory service side of TDC is just fine) you can go ahead and check
manual was handed down to Moses along with the Ten your valve lash.
Commandments, are simply parroting that material.
It’s not necessarily wrong; it’s just painfully slow and I hope this all makes sense to you; it is actually allot
amateurish. quicker to do than it is to describe.
It’s nothing more that rotating the engine to a position
First, don't worry about finding exact TDC-Compres- where all the valves are closed… the position of the
sion (top dead center-compression). piston is being used only as a point of reference rela-
Both intake and exhaust valves must be closed for sev- tive to the valve train.
eral degrees before and after TDCC, otherwise there When you reach the point where the rocker covers are
would be no compressed mixture to ignite, and conse- off and the plug is out... it takes about 30 seconds to
quently, no power stroke. do the rest... honest.
A four-stroke engine's intake valves open a few de-
grees before TDC-Intake, at the end of the exhaust Part Three. Inspecting/adjusting valve
stroke, and close several degrees after the BDC-Intake,
which is the beginning the compression stroke. lash
What you are checking is the clearance (lash) between
The "Easy Way" the rocker arm threaded adjuster pad and valve stem
When you have taken off enough parts to see the It should be .006" cold. Too much, and you have
rocker arms and valves, do as follows: noise, the potential for damage and a reduction in cam
timing duration with the subsequent loss of power. Too
Elevate the rear wheel, make sure you have removed little, and you have the potential for damage. This is
the spark plug and then shift the bike into 5th gear. where the right feeler gauge comes into play.
Rotate the rear wheel in the forward direction a few
revolutions, and watch the rocker arms open and close Addendum 9-16-07: Although .006" (.15mm) is quite
the valves... see how that works? probably the most common LC4 lash spec... please
refer to your service manual for the correct lash.
Disregard the auto de-compressor “clack”… it won’t KTM has, over the years has adjusted the lash up and
hurt you. down and in the past few years have provided a range
(.012mm - .015mm) of lash adjustment.
Turn the rear wheel very slowly, right after the intake
valves open, and then close... STOP! To do this job as quickly and easily as possible, you
OK, good so far. You are now somewhere after should have the right feeler gauge; the Motion Pro
BDC-C (bottom dead center, compression) and ap- design is the best and only way to go, unless you are a
proaching TDCC. cheap bastard like me, and want to make a "copy" of
the Motion Pro.
Put a soda straw in the spark plug hole until it rests on
the piston, slowly turn the rear wheel and watch the The Motion Pro gauge has a stiff metal "handle" about
soda straw rise up the plug hole. At this point, if you 3 inches long and a short (about ½”) narrow blade riv-
want you can use a focusing flashlight to actually see eted to each end, bent at about a 90º angle. (You will
the piston rising in the cylinder on its way to TDC. want to readjust the blade to a "less severe" angle)
If you overdo it, and go past TDCC and the piston How do you make a valve lash feeler gauge? Easy.
starts to go back down, simply turn the rear wheel Simply take a .006" feeler gauge blade and epoxy it
backwards a bit. between two thicker blades to make the handle, with
approximately ½" of the .006" blade extending past it.
Weather you check the valves a bit before or a bit after Put about a 45º angle on the blade and your ready to
TDCC is no big deal, as the valves are closed for sev- go. See figures 1 and 2.
eral degrees both before and after TDCC.
If you find that it requires a bit more effort than de-
The idea is that with the space you have to work in be- scribed in the tape roll analogy to move the blade back
ing very "limited", the stiff handle offers more control and forth, you have a “tight six”… closer to a .005"
and eliminates blade flex and bending... problems as- clearance.
sociated with a conventional feeler gauge blade. If you can slide it back and forth easily, with only
slight resistance you have a “loose six”… closer to a
When I have either of the above described “feels”, I
call it good and record my clearances for future refer-
ence and to track any valve clearance “trends”.
If your feel goes beyond the described limits, then it’s
time to readjust the lash to within specification.
If you need to make an adjustment, even if it’s only
Doing it… What Meat refers to as “The Mo- on one valve, you will want to loosen both jam nuts.
ment of Truth” I’ve found that due to the rocker arm’s clearance on its
shaft, the adjustment and feel on one valve can affect
When you first insert the blade into the clearance the other… besides, if you’re reading this, you could
between pad and stem tip (figures 3, 4, and 5), it may probably use the practice.
take an unusually high bit of effort to do, ignore this,
and pay attention to the “feel” of the blade after inser- When you loosen the jam nuts, unless you have the
tion… a bit of drag, or resistance on the gauge is what previously mentioned ¼” drive torque wrench, you
we are looking for. will want to note the effort required to do this as you
will attempt to replicate the original torque value by
Slide the blade back and forth a bit to get a feel for the feel.
resistance, It should be like… how to describe feel?
Do you have a roll of scotch tape? Slowly pull some If you do have a ¼” torque wrench, find an easily
tape off the roll… feel the resistance? Kinda like that. accessible fastener of the same size on your bike and
torque it to 12 ft-lb., now lay a wrench on it and get a
feel for that value. When you re-torque the jam nuts,
try to duplicate that value by hand. adjustment. When it feels right, and the jam nuts are
“torqued” and it still feels right… Congratulations!!!
You’re almost done.
You can still do this job with a regular feeler gauge
blade if you so choose, but it is very difficult if not im-
possible to "check" the clearances. I have done it both
ways and prefer the “check” method to the “manda-
About all you can do is back off the adjusters, place
the conventional blade into the excessive gap and run
the adjusters down onto the blade, check the feel and
tighten your jam nuts.
Once the valve seats and valves have "broken in", (a
few thousand miles) the adjustment doesn't change
much... it's much quicker to check the clearance with
the Motion Pro gauge or homemade version than a
Figure 4 mandatory re-adjustment of the clearance every time.
Give yourself lots of time to do this task if it’s your
first time. Double, triple check everything as you
go, be methodical and orderly... you'll be fine. Once
you've done it a few times, you will find the entire
process can be performed in a about an hour... give or
I seldom rush. What is the carpenter’s first rule? Mea-
sure twice, cut once.
When putting everything back together, simply reverse
the steps. Don’t over torque any fasteners and don’t
forget to install new zip-ties where needed. A bit of
light grease on the four round tank rubber mounts help
the tank to slide into place a bit easier.
When you light it off after finishing, and everything
sounds as it should, have a cold one, give the dog and
cat a treat for not getting in your way and give your-
self a pat on the back for a job well done.
Chris 'Creeper' Hickson
Something you will notice is that when you re-tighten
the jam nut, the lash actually loosens slightly; this is For their assistance in editing this guide and offering
from the nut pulling the adjuster stud hard up against their input, I’d like to thank:
You will undoubtedly tighten and loosen the jam nut Drif10
several times, checking the feel each time… This Meat Popsicle
is fine; I do it myself every time I have to make an ChrisC
Loadedagain Pro gauge or copy of one... that and it's a hell of a lot
Dagwood quicker to not adjust the ones that don't need it.
Rad On to the first method, the "X turn equals X thou-
Passmore sandths" method.
Addendum for 03-07-06: At the request of a member, There is a "surprising" issue of consistency. You would
the information below has been added. References to think that in both theory and practice, a degree of turn
the LC4 engines "typical" valve train wear is based (in this instance 1/4 turn equals 0.15mm) would equal
on personal observation as well as the observations of a consistent quantity of movement in the adjuster stud
others. (or any machine fastener for that matter) but it is usu-
ally not the case.
Why valve lash changes.
Variables enter the equation. Variables in the engage-
The "peaks and valleys" of the freshly machined seats ment of opposing threads, torque induced binding, ball
and valves compress into one another and the avail- & socket wear, valve stem tip and adjuster pad wear...
able lash is taken up as the valve receeds slightly into plus the inconsistencies in wear patterns as compo-
the seat. nents shift, rotate and develop small but new and
different wear patterns. You don't really know what the
The LC4s usually need to have their clearances reset lash is... you only assume it is correct.
at around 1000 miles, give or take.
As the miles increase, unless you ride at redline often, In a pinch, I've done the x turn equals x distance
the lash settings will begin to stabilize and an actual method of lash adjustment... and it got me home, but
adjustment will become less frequent. I've found it to be not completely reliable, and the
You'll often find that "checking" the lash may be all more wear in the parts, the less accurate it is when
that is required, and the reason I recommend using a compared to a feeler gauge.
Motion Pro gauge, or homemade copy.
So my question is, when you're sitting in your shop,
Should you check the lash and discover a substantial garage, kitchen floor what have you, and your inten-
difference from the correct setting, this is an indicator tion is to do a good and accurate job... why do it less
of a possible problem. accurately than you have the capability to?
A reduction in lash could be caused by valve stem
stretch, valve seat compression and valve head war- So there you go.
page or distortion.
An increase could be caused by cam, rocker arm fol- Addendum 3-23-07: In the '07 KTM 640 Adventure
lower, rocker adjuster stud and elephants foot, rocker owners manual (and I assume all other LC4 manuals)
shaft and valve stem tip wear... or failure. the valve lash spec is no longer a single number, but a
rather large variable.
Addendum 7-14-2006: I've been asked why not just
back off all the jamb nuts and set the valve lash us- 0.12 - 0.15mm
ing the "X turn equals X thousandths" method, or, the
"regular" feeler gauge method. The upper range remains the same as the older spec.
There are several reasons why not. I'll respond to the The lower range is what's new.
last method first. I don't know at this time if the spec is "retrofitable",
or if it is specific to the '07 (and possibly the '06)
When you back off all the adjusters, you have no idea model year only. A change in metallurgy, fitment of
what clearence you had previous. Was it loose, was it corresponding parts, or even mean average operating
tight... don't know do you, and you don't know what temperature could limit the new spec to just the cur-
that condition of your valve train is. That in and of rent year.
itself is justification for measuring first with a Motion
Use the lower spec on older bikes at your own risk.
That’s all I got,