Newibe to the whole valve thing, Really need some start-up info

Ok well coming off a RM250, I have the whole valve thing to worry about. I need some info like what feeler gauges to use and where I can buy them. I also need info like the whole process of knowing what shim sizes are needed to be ordered and also I need to know how you can tell when its time to check or adjust the valves. Thanks. PS, Im sure I'll be having some more questions so dont be surprised to see me again. Also the bike I own is an 05 YZ450.

Welcome!! Try look for item #f804p under tools, they are the NARROW metric feeler gauges you will need for 6.99 plus shipping. As for the shims your local YZ dealer will have them. And you wont know what size you need till you find out the sizes installed in your bike. I checked mine after 5 hours, but the dealer told me to wait for about 10 hours. Check"em after 5. Keep your air filter clean and change your oil often. Dont wait for them to look dirty. Price of a quart is cheap insurance!!!!

Unfortunately, the only way to know what size shims to order is to measure the clearance and then pull the cams and see what is in there now.

First, though, you probably have a long time to think over your approach to the problem. My '03 is STILL in spec, so I have never adjusted it. I did the first ever adjustment on my '01 250F late last year, and haven't had to re-do yet.

A couple of little things to remember:

Service shims are only available in increments of .05mm, but the factory has access to shims in .01mm increments. This will drive you nuts deciding what to do with a valve that's at or barely below the low limit and has, say, a 186 in it. Do you use a 185 or a 180? Don't get too caught up in it. .05mm is about .0025 of an inch, so each .01 is less than half of one thousandth. Pretty small.

"Normal" automotive feeler gauges will work on a 450 (they need to be trimmed for the center intake on a 250F). They're usually labeled in both english and metric units, and you should have one close enough to the right metric size to work. Obviously, the metric ones are the best, though, so get them if you can.

Here's a link to the thumperFAQ site writeup (includes links to others, too) It's for a 250, but except for the specs, it's the same process.

Be very careful retorquing the cam caps. Do them in small increments, and use an in/lb wrench.

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