Valve Adjust Procedure for YZ250F/YZ400F/426F/450F

The first and foremost thing you need to do before even taking your seat off is...a clean bike. I broke the rule here because you can see that my bike is partially dirty! You will need a few rags, a towel or clean table to keep all your parts and all the tools necessary. 8,10,14,17mm T-Handles work fine, as well as a 5mm allen to remove the valve cover and then feelers. If you do need to adjust the valves, then the proper shims will be needed. 7.48mm shims for a 250f and 9.48 shims on a 400/426/450.

The next step is easy, take the seat off, and then your gas tank and shrouds off.



Before Yanking on that tank when its all unbolted, make sure you turn off, then disconnect your fuel line!



This is where I choose to put all my parts and tools on. Make sure its a clean towel!



After getting the seat and tank off, you will need to disconnect your spark plug wires, and on a 4 stroke pull that huge rubber grommet that protects from debris from dropping down there.



Next, you are almost ready to remove the valve cover, but first you will most likely want to remove the upper motor mounts to make things more open and accessable.





Next, take you 5mm Allen and loosen the 2 bolts holding the valve cover on. Also, before you pull the valve cover off, pull the breather hose off.



Now, pull the valve cover off and verify you are at TDC.

Look closely at this picture and see that on the intake cam, there are 2 dots in line with the cylinder head and on the exhaust cam, the dot is also in line.



Another way to verify TDC is by the cam position. Make sure they are facing out!



Checking the Valves: Now look in your manual and see what the valve clearance should be. Note- The clearances shown are for a 2006 YZ250F



Now here's the fun part, checking the clearances. Get your feeler gauge out and measure your clearances.

Shown Measuring Right Intake - Record clearances


Shown Measuring Right Exhaust- Record clearances


If you clearances are in spec, then all you need to do is put everything back together and ride!
If your clearances are not in spec, then continue reading.
 

Adjusting the Valves.

Now take off your cam chain tensioner and get a zip tie or similar and tie your cam chain up just to make sure it cannot fall when you take your cams out.



Now its time to take your cam towers off. When you loosen your cam towers, make sure you go in a star pattern or else you could warp them.



When you get ready to pull the cam tower, stuff something in all the open areas, preferably a rag, because there is a C- spacer in between the tower and the cam.



Then just do the same for the other cam tower...



Be careful pulling your cams out, and just make sure the cam chain is tied up so it wont fall down into the motor.





Now you need to pull the bucket out and the shim. Most times the oil will hold the shim on the bucket, just be careful because if your shim drops in the motor, have fun getting it out!



My best advice is to make some sort of chart to keep the buckets and shims in the correct order because putting the bucket back in where it came from is a must! Do not mix and match here.



Here is my assortment of parts, make sure they are on something clean!



Now that you know your valve clearances, you can see exactly what shim size is in there. You will need to go to the shim size chart in your manual to get the right size shims.

Put the right size shims in and re-assemble everything. For me, putting everything back together is easier then taking it apart.

I cannot stress how important it is to make sure you have not turned your motor over at all! And you absolutely need to put your cams in the right way, line the dots up, lobes facing out.



Now put the towers back on and re-torque everything back down in a Star pattern! Torque to 75 inch lbs.





Now that your cams are in, and the cam towers, reset the cam chain tensioner. Once that is set, your ready to put the valve cover back on. Once the valve cover is back on, everything is just how it came off, simple. Just take your time and double check everything!

Cant even tell I took it apart!



Now, this is what I did just to be safe. Sometimes people can mess up putting their cams in, or who knows what, but very carefully kick the motor over to make sure nothing is binding. If everything is good, then you are good to go.

Here is my video after the Adjustment. I hadn't started my bike since last Wed (3/5/08) and today is the 11th.

 

very nicely done pin_it, excellent step by step, clear pics. BRAVO!!!! could you add a pic of the timing mark for the crank??. do the cams move when the tensioner is reinstalled??  

Autismspeaks.org
Gilbert AZ
06yz144,05yz85,02yz85

Awesome write-up!!!!  So cool you took the time do document this for everyone!!

Out of curiousity - were any of your valves tight, and how many hours were on the motor since the last time you had to adjust the valves?

Thanks again!  
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Here we go again!

Excellant job.  How can you tell if the feeler gauge is too tight or loose?  How much play is acceptable?  

Bill H.
Temperance, Mi
2000 CR250R
1991 YZ125

I think you will find, and pin_it will probably tell you the same thing, is when using feeler gauges, it will either fit, or it won't. You don't force the gauge in. The valves on bikes always get tighter as the valve seats wear and the tip actually gets closer to the cams. If the recommended feeler won't slide in without play, use progressively thinner feeler gauges until you find one that fit. Record the number, once you get the shim out you will need to measure the shim. Subtract your feeler gauge thickness from the required specification,(i.e. .15 spec minus .08 as measured = .07) choose a new shim that is the same amount thinner to bring your valves into spec.  

Pin it...Great job,Great pics, Great info! Thats the way to give great step by step. Thanks for taking the time to do it. I'm shure Dave will want to sticky this !  
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DIABETES SUX!

MJP68:
very nicely done pin_it, excellent step by step, clear pics. BRAVO!!!! could you add a pic of the timing mark for the crank??. do the cams move when the tensioner is reinstalled??

I will try to add a picture of the mark on the crank, but I have never used that mark when getting TDC, its just as easy by the way the cams are and the marks on them.

The cams do move just a little when the tensioner is installed, but just barely so that all the chain slack will be eliminated.  

Its almost impossable to get a picture of the mark, but here is the best I could do ...



I use photobucket and when you go to resize the picture, you can resize them to a preset "Message Board" 640X480...so thats what I used.  

skipkh:
Awesome write-up!!!!  So cool you took the time do document this for everyone!!

Out of curiousity - were any of your valves tight, and how many hours were on the motor since the last time you had to adjust the valves?

Thanks again!

yes, all of my valves were tight. All 3 intakes were at .07mm and my exhausts were left .12mm and right .15mm. The YZ/F's like their valves on the tighter side, so I tried to shim them all to the tighter end of the spectrum but just in spec.
Oh and my bike has 9.2 hour on the meter.  

bhorrigan:
Excellant job.  How can you tell if the feeler gauge is too tight or loose?  How much play is acceptable?

Yup, RingDing pretty much summed it up. The clearance is so small that even .01mm off and you will know if it fits or not. Thay are also flimsy, so you can't really force them in.  

I use Feeler gauges on my cars and bike. Great for timing set and ect...As said, it will fit or not.
You want a good fit with no room.  
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DIABETES SUX!

thanks, i thought it would be a tough pic to take but i think all timing marks should be double checked prior to final assembly.(no matter how carefull we are during the repair)  

Autismspeaks.org
Gilbert AZ
06yz144,05yz85,02yz85

Nice job pin_it. I have 3 bikes to do this on and was going to attempt what you did, now all I have to do is read. Thanks.  
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I love this dirt stuff.

This couldn't be better. I was just getting some info from Skip yesterday about tightening valves and he was a big help, but this coundnt have come at a better time. I didnt know exactly what I was getting into and now it is crystal clear. Thanks for taking the time, I wish all repairs came with instructions like this.