How to shim the valves on your 250 (w/pics)

[Heckler]

First off I will begin where I left off with the valve check post, if you haven’t seen it yet start there.

Valve Check Post

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 work.

Spreadsheet

Remove the bolt on the cam chain tensioner.

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.

Remove the cam cap bolts in steps in a criss cross pattern, loosen a little at a time to avoid warping the caps

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 case.

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.

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 dont need to remove the cam or cam caps, you will need to remove the cam cap bolts but thats way easy...

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 ones.

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.

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 criss cross 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 whole assy.

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.

Put everything back together in reverse order. Now save yourself some money and do this yourself. It really is very easy.

Heckler

[IMCanadian]

Great post!!! Thanks a million...fortunately my valves are still in spec but based on your post I think I could shim them myself.

[Throttlejockey]

Great job Heckler. ?

Maybe you'll save some of these guys some money.

Only thing I see wrong is this quote.

If the writing has worn off you will need to use a caliper or dial indicator to get the size, you will need this to calculate your new shim size.

I'm not trying to being a jerk but you would use a dial caliper or a micrometer to check the size. ?

[RMark]

Beautifully done ?

I've read the Dirt Rider article explaining the same with diagrams, but your pic's and explanation do indeed make it seem quite clear. Not that I'm looking forward to the job, but knowing ahead of time what's involved takes the mystery out of it.

Thanks ? :cry:

Mark

[ReaperAZ]

One word... STICKY!

Heckler pulls through again. Awesome pics again, great job man. ?

Dano

[Heckler]

I'm not trying to being a jerk but you would use a dial caliper or a micrometer to check the size.

I can fix that...

[sled_rider]

Great job. My valves were spot on after about 700 miles. With this info, your spread sheet and the manual this looks like an easy job. The Spread Sheet is a must for everyone to use. Thanks ?

[wheelsoff]

Also FYI if your Honda dealer doesn't have the shims you need the YZ250F shims are the same.

[tasc]

Excellent post, great info, please sticky this!

[The_Blue_One]

Great post Larry ? I hope ya don't mind i added it to your checking valves post and edited the title ?

[E-Ticket]

One option for your procedure, Larry:

= if you only need to adjust *just* the exhaust valves, you can:

=== a) remove the cam and then tilt the exhaust rocker back. (With the cam removed there is now enough slack to get at and remove the shims)

...............OR.......

=== ? remove the cam holder bolts, leave the cam in place (easiest), and then pull the access cover and slide out shaft for the exhaust rocker arm assembly. You can then lift off the exhaust rocker arm assembly and get at the shims.

Great tip on the magic marker on the cam gear and cam chain!

(...sound of hand slapping forehead, "but of course!")

Thanks, dude! - RandyB ?

[Smole]

What a great post and how to calculate the proper shims. I have about 250 hours on mine and unable to shim the intakes anymore. In the process of replacing the valves and replacing the piston (ring holder) while it's apart.

[jaso]

Excellent Job !!! If more guys did this the shops might get a little more reasonable or honest.Next please change the piston out Ha Ha. ??

[The_Blue_One]

Excellent Job !!! If more guys did this the shops might get a little more reasonable or honest.Next please change the piston out Ha Ha. ??

What pics do you want of that? ? I have motomanfan's bike in the garage right now tore down and waiting on parts to change the piston.

Heckler and i could easily recreate tearing it down and do a step by step on the process. I'll tell him to bring the camera when the parts come in ?

[jaso]

Ya, that would be great!I just thought since he has gone this far heck why not just add to it as you work on it.Yes this did help me out alot it was a piece of CAKE and this was my first time I had about 45 hours at fast intermediate level riding. Ext were 0.06 off intake was 0.03.OHH ya whats up with the little RED billet part by the ext pipe and THANK YOU VERY MUCH just remember what comes around goes around. ?? :cry:

[TheWeez]

Heckler, you are the man. Thanks for taking the time to document your work. You have really helped me out. I used your checking procedures and it went without a hitch. Now that I've read your shimming procedures, I feel very confident I can do this myself.

? :cry:

[js3324]

You would be a HERO to thousands of people if you could do that (explaining step by step how to replace the pistons or valves if you would be AWESOME to) with pictures. Seriously, you would be a god, lol Heckler already is, and just wow! Thanks alot, it is alot simpler then it appears

Oh and what dirtrider was shimming / or replacing the piston was that in? september?

[ThumperWrench89]

Great great job. That will help me out soo much. Thank you. ? :cry: ? :cry: ???

[spuj]

By the look of the pics in this guide you don't have to remove the bolts on the cam-sprocket to get the chain of, is that correct? That would make things easier for sure..

[skipn8r]

By the look of the pics in this guide you don't have to remove the bolts on the cam-sprocket to get the chain of, is that correct? That would make things easier for sure..

Correct. Once you slide the bearing on the cam to the left, the left end of the cam drops down allowing you to remove the chain. Note easily, but do-able.