KTM LC4 valve lash inspect and adjustment
 It's easier than it looks... honest
Updates and Addendums at end of article.

How to inspect the valves on a KTM LC4... In three easy steps.

This DIY guide is for new LC4 ('07 and earlier) owners who might have some degree of trepidation when it comes to this task.
I have written the steps to this process individually several times, but have never put it all together in one bite, until now.

This has been written for someone that has fair to good general mechanical aptitude, but has limited experiance at this task.
If you're reading this with intent... and you're never spun a wrench, you are a brave soul. 
If you can take your bike apart and put it back together... and it still runs, you may find this mildly entertaining, but by no means, new information.

Part One. Getting there.

We will use the 640 Adventure as our example, as it is the most complicated to "field strip" model of LC4, and the one I happen to own. It is also the model that many of the folks reading this will own as well.
If you own an SXC, SMC or LC4E, the vast majority of this information still applies, you simply have fewer parts to remove and reinstall. Lucky you. 
No doubt there are some variations from year to year, but I don't believe they will be too much of an issue. Older LC4s may have different valve lash specs than more recent models… check your owners manual to verify the specs for your bike.
Some of the information provided is basic 4-stroke theory & design, and may apply to brands and models other than KTM.

Tools & Parts

1. A Motion Pro valve lash feeler gauge (.006" or 0.15mm) or reasonable facsimile.

2. A set of metric Allen wrenches. You may find it necessary to "cut down" the short end of a few of your Allen wrenches to improve access to some fasteners. As an alternative to cutting down Allan wrenches, if you have a small ¼" ratcheting wrench and short metric Allen insert bits... much like cut down Allens, they can really come in handy on some of the limited clearance rocker cover bolts.

3. A set of metric Allen sockets, preferably ¼" drive.

4. A set of metric sockets, again, preferably ¼" drive.

5. A ¼" drive ratchet and extension assortment.

6. Miscellaneous hand tools such as screwdrivers, pliers, band-aids and so forth.

7. I'm not going to list a torque wrench because most folks don't own a 3/8" torque wrench, let alone the more preferable but not so easy to find ¼" torque wrench.

8. New rocker cover gaskets (yes, you can reuse the old ones, once… if they are in real good condition)

9. Now would be a good time to consider replacing the spark plug if it has 5K miles or better on it.

10. Some Zip-ties in assorted sizes.

Why a ¼" drive set rather than the more common…3/8" drive? The third rule of professional mechanics is to use the smallest tool that will reasonably do the job.
Most fasteners on the LC4 engine are small and have relatively low torque values, there are no fasteners on this job that require using the larger, bulkier, and with greater potential for “excessive leverage” 3/8" drive set.

Proper Atmosphere That’s right… atmosphere.  

What I mean, is a well-lit and relatively clean environment where you will not be distracted or disturbed. A separate clean space away from where you will be working, to safely store the parts that you have removed.
Nothing more entertaining than turning around suddenly, startled from your dog chasing your cat thru your tools, and kicking your gas tank across the room or, if the tank was full, breaking your big toe so badly you need morphine.   

I will not waste your time outlining the details of things like tank or fairing removal, if you can’t do these tasks, you may want to take your bike to a Dealership or a trusted and mechanically inclined friend, with a copy of this guide.

Is your motorcycle clean? If not, after removing item four, you may want to give the engine compartment a little bath. Don’t want big chunks of dried mud or little rocks falling in your motor, do you?
Is your motorcycle engine at room temperature? Don’t perform this task 45 minutes after riding into the garage. It takes several hours for an entire motorcycle engine to cool to room temperature.

You will need to remove the following parts from the motorcycle.
1. Seat. (One bolt)

2. Outer fairing (Six bolts. two turn signal electrical connectors)

3. Fuel tank. You do not have to remove your inner dash, but it helps to get it out of the way for tank removal. Use tie straps or elastic cord to tie the “ears” of the dash up to the handlebars. (One nut. three fuel hoses. one vent hose, if any)

4. Cooling fan. Don’t force it; it comes out easy once the back tabs are popped from behind the radiator. (Two screws. one electrical connector)

5. Front rocker cover-to-frame vent hose. (Two screw clamps)

6. Rocker covers. Save the covers as the next to last parts you remove or disconnect. (Three screws each, watch the washers)

7. Spark plug. Save this as the last part you remove or disconnect. If you have a compressor, blow out the plug recess thoroughly prior to pulling the plug.

8. It is not necessary to remove the radiators. It does make access a bit easier, but it is a trade off in time and hassle.

You will need to partially remove and hold away the following parts from the motorcycle.
1. Capacitor (one bolt)

2. De-compressor cable (back off adjustment and disconnect from lever... you can leave the cable attached to the front cover or remove it... your choice)

3. You may need to snip a zip-tie or two along the way, to move a harness or cable out of the way.

4. See items 6 and 7 above.

5. At this point, you should have more than adequate access to the four rockers and their adjusters. If not, one of us has forgotten something and it might not be you, because yes, I am doing this from memory. 

Updated information as of 01-14-06
Now that you have all the odds and ends out of the way, you may notice that you have a bit of oil leaking from the rocker cover. If this is the case, and you want to fix the leak… take a look at

That’s it, on to part two.

Part two. Finding TDCC

Addendum: A more complete description of finding TDC-C is available for those that need it. It can be found here.

A great deal has been written in this and other forums about finding TDC-C. Some descriptions are quick and easy, written by and intended for people who have a good grasp of how a 4-stroke engine works.
Other descriptions, written by some well-meaning folks who undoubtedly think that the factory service manual was handed down to Moses along with the Ten Commandments, are simply parroting that material.
It’s not necessarily wrong; it’s just painfully slow.

First, don't worry about finding exact TDC-Compression (top dead center-compression).
Both intake and exhaust valves must be closed for several degrees before and after TDCC, otherwise there would be no compressed mixture to ignite, and consequently, no power stroke.
A four-stroke engine's intake valves open a few degrees before TDC-Intake, at the end of the exhaust stroke, and close several degrees after the BDC-Intake, which is the beginning the compression stroke.

The "Easy Way"

When you have taken off enough parts to see the rocker arms and valves, do as follows:

Elevate the rear wheel, make sure you have removed the spark plug and then shift the bike into 5th gear. Rotate the rear wheel in the forward direction a few revolutions, and watch the rocker arms open and close the valves... see how that works? 

Disregard the auto de-compressor “clack”… it won’t hurt you. 
Turn the rear wheel very slowly, right after the intake valves open, and then close... STOP!
OK, good so far. You are now somewhere after BDC-C (bottom dead center, compression) and approaching TDCC.
Put a soda straw in the spark plug hole until it rests on the piston, slowly turn the rear wheel and watch the soda straw rise up the plug hole. At this point, if you want you can use a focusing flashlight to actually see the piston rising in the cylinder on its way to TDC.
If you overdo it, and go past TDCC and the piston starts to go back down, simply turn the rear wheel backwards a bit.
Weather you check the valves a bit before or a bit after TDCC is no big deal, as the valves are closed for several degrees both before and after TDCC.
Once you are near TDC (about 6 to 9mm from either side of TDC is just fine) you can go ahead and check your valve lash.

I hope this all makes sense to you; it is actually allot quicker to do than it is to describe.
It’s nothing more that rotating the engine to a position where all the valves are closed… the position of the piston is being used only as a point of reference relative to the valve train.
When you reach the point where the rocker covers are off and the plug is out... it takes about 30 seconds to do the rest... honest. 

Part Three. Inspecting/adjusting valve lash

What you are checking is the clearance (lash) between the rocker arm threaded adjuster pad and valve stem tip.
It should be .006" cold. Too much, and you have noise, the potential for damage and a reduction in cam timing duration with the subsequent loss of power. Too little, and you have the potential for damage. This is where the right feeler gauge comes into play.

Addendum 9-16-07. 
Although .006" (.15mm) is quite probably the most common LC4 lash spec... please refer to your service manual for the correct lash.
KTM has, over the years has adjusted the lash up and down and in the past few years have provided a range (.012mm - .015mm) of lash adjustment

To do this job as quickly and easily as possible, you should have the right feeler gauge; the Motion Pro design is the best and only way to go, unless you are a cheap bastard like me, and want to make a "copy" of the Motion Pro.
The Motion Pro gauge has a stiff metal "handle" about 3 inches long and a short (about ½”) narrow blade riveted to each end, bent at about a 90º angle. (You will want to readjust the blade to a "less severe" angle)
How do you make a valve lash feeler gauge? Easy. Simply take a .006" feeler gauge blade and epoxy it between two thicker blades to make the handle, with approximately ½" of the .006" blade extending past it. Put about a 45º angle on the blade and your ready to go.

The idea is that with the space you have to work in being very "limited", the stiff handle offers more control and eliminates blade flex and bending... problems associated with a conventional feeler gauge blade.


When you first insert the blade into the clearance between pad and stem tip, it may take an unusually high bit of effort to do, ignore this, and pay attention to the “feel” of the blade after insertion… a bit of drag, or resistance on the gauge is what we are looking for.

Slide the blade back and forth a bit to get a feel for the resistance, It should be like… how to describe feel? Do you have a roll of scotch tape? Slowly pull some tape off the roll… feel the resistance? Kinda like that. 

If you find that it requires a bit more effort than described in the tape roll analogy to move the blade back and forth, you have a “tight six”… closer to a .005" clearance.
If you can slide it back and forth easily, with only slight resistance you have a “loose six”… closer to a .007".
When I have either of the above described “feels”, I call it good and record my clearances for future reference 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 on one valve, you will want to loosen both jam nuts. I’ve found that due to the rocker arm’s clearance on its shaft, the adjustment and feel on one valve can affect the other… besides, if you’re reading this, you could probably use the practice.

When you loosen the jam nuts, unless you have the previously mentioned ¼" drive torque wrench, you will want to note the effort required to do this as you will attempt to replicate the original torque value by feel.   
If you do have a ¼" torque wrench, find an easily 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.

Something you will notice is that when you re-tighten the jam nut, the lash actually loosens slightly; this is from the nut pulling the adjuster stud hard up against its threads.
You will undoubtedly tighten and loosen the jam nut several times, checking the feel each time… This is fine; I do it myself every time I have to make an 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 impossible to "check" the clearances. I have done it both ways and prefer the “check” method to the “mandatory” method.
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. 

Almost home

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 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 take.
I seldom rush. What is the carpenter’s first rule? Measure 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 yourself a pat on the back for a job well done.   


Addendum for 03-07-06

At the request of a member, the information below has been added. References to the LC4 engines "typical" valve train wear is based on personal observation as well as the observations of others.

Why valve lash changes.

The "peaks and valleys" of the freshly machined seats and valves compress into one another and the available lash is taken up as the valve recedes slightly into the seat.
The LC4s usually need to have their clearances reset at around 1000 miles, give or take.
As the miles increase, unless you ride at redline often, the lash settings will begin to stabilize and an actual adjustment will become less frequent.
You'll often find that "checking" the lash may be all that is required, and the reason I recommend using a Motion Pro gauge, or homemade copy.

Should you check the lash and discover a substantial difference from the correct setting, this is an indicator of a possible problem.
A reduction in lash could be caused by valve stem stretch, valve seat compression and valve head warpage or distortion.
An increase could be caused by cam, rocker arm follower, rocker adjuster stud and elephants foot, rocker shaft and valve stem tip wear... or failure.

Addendum 7-14-2006

I've been asked why not just back off all the jamb nuts and set the valve lash using the "X turn equals X thousandths" method, or, the "regular" feeler gauge method.
There are several reasons why not. I'll respond to the last method first.
When you back off all the adjusters, you have no idea what clearence you had previous. Was it loose, was it tight... don't know do you, and you don't know what that condition of your valve train is. That in and of itself is justification for measuring first with a Motion Pro gauge or copy of one... that and it's a hell of a lot quicker to not adjust the ones that don't need it.

On to the first method, the "X turn equals X thousandths" method.

There is a "surprising" issue of consistency. You would think that in both theory and practice, a degree of turn (in this instance 1/4 turn equals 0.15mm) would equal a consistent quantity of movement in the adjuster stud (or any machine fastener for that matter) but it is usually not the case.
Variables enter the equation. Variables in the engagement of opposing threads, torque induced binding, ball & socket wear, valve stem tip and adjuster pad wear... plus the inconsistencies in wear patterns as components shift, rotate and develop small but new and different wear patterns. You don't really know what the lash is... you only assume it is correct.

In a pinch, I've done the x turn equals x distance method of lash adjustment... and it got me home, but I've found it to be not completely reliable, and the more wear in the parts, the less accurate it is when compared to a feeler gauge.
So my question is, when you're sitting in your shop, garage, kitchen floor what have you, and your intention is to do a good and accurate job... why do it less accurately than you have the capability to?

So there you go.

Addendum 3-23-07
Howdy folks...

In the '07 KTM 640 Adventure owners manual (and I assume all other LC4 manuals) the valve lash spec is no longer a single number, but a rather large variable.

0.12 - 0.15mm

The upper range remains the same as the older spec. The lower range is what's new.
I don't know at this time if the spec is "retrofitable", or if it is specific to the '07 (and possibly the '06) model year only. A change in metallurgy, fitment of corresponding parts, or even mean average operating temperature could limit the new spec to just the current year.

Use the lower spec on older bikes at your own risk.

That’s all I got... hope it helps someone in LC4 land.