07 yz450f Valve adjustment

First of all I would like to thank all of the posters for the vast knowledge that is on this site. I have been reading posts for hours each day and I am learning all the important stuff to do with a four stroke. I decided to check the valve specs and one thing when I was setting the piston to top dead center according to the reference marks (9:00 oclock and 3:00 oclock marks along with the flywheel mark through the site hole) and when counting the pins between the two twelve oclock marks there is 13 pins not twelve? I counted them numerous times and still come up with 13, how is this possible?? All the valves were in spec except one intake valve which I will shim in the morning after I get some shims from the local shop. But back to the cam chain is there a problem?

maybe 1 of the pins you are counting, you shouldnt be counting, as in, the pin is kind of on the camchain wheel.

got pics?

I will take some tonight when I get home. The bike runs awesome and starts on the first kick. Maybe I am worried about nothing but I want to make sure.

The cams are NOT timed by counting pins between the two 12:00 marks unless you're putting an OEM 450 cam in an earlier model.

Set the crank at TDC, and align the 9:00 mark on the exhaust cam and the 3:00 mark (I) on the intake with the top surface of the head. Back all 3 shafts up about 3 degrees, and slowly roll the crank forward to TDC again. Check the marks for alignment.

Once this is right, if you are working on a 400, 426, or 450, you'll usually notice there are 13 pins between the two 12:00 marks. If it's 12, either one of your cams doesn't really line up, or your bike is really a YZ250F. Even this isn't dependable across the board, as some earlier 400's and WR's come out differently.

The pin count between cams is basically meaningless except in the 450 cam swap, or as a cross check, because all it tells you is that the two cams are in the right relationship to one another, when what's really important is how they sync up with the crank. Knowing the pin count is useful when reassembling the cam chain, though. When putting one of these together, the first cam is easy, but to get the second one in place, you have to set it in the center of the head, drop the chain over it, and roll it down into place in its saddle. You can set the exhaust first, then throw the chain over the intake, counting out pins as you do. This gives you a very good chance of getting the timing on the second cam right on the first attempt (something that often frustrates new guys). But you still have to double check by using the "real" timing marks at TDC.

Once this is right, if you are working on a 400, 426, or 450, you'll notice there are 13 pins between the two 12:00 marks. If it's 12, either one of your cams doesn't really line up, or your bike is really a YZ250F.

The pin count between cams is basically meaningless except in the 450 cam swap, or as a cross check, because all it tells you is that the two cams are in the right relationship to one another, when what's really important is how they sync up with the crank.

how very very very true richard.

can we put this is flashing neon someplace? !!!

I started my reply with, "I guess we have to do this again", but my mother's ghost made me leave it out. :thinking:

Thanks for the info. I was mislead by the thread that said to make sure that their are 12 pins between the two marks. Well i guess my first post was a newbie mistake that will not happen again. You are right this topic has been covered numerous times but I couldn't find reference specific to the 07 bike and since being new to four strokes (always had 2 strokes prior and will never go back) I wasn't sure if the motor has changed when they did all the other changes in the 06-07 bike.

Regarding the timing marks.... when I look through the window on the crank case there is what looks like a H and right next to it is a l which is the mark shown in the book. Is the H another reference point for something else?

The "H" is a test reference point for checking the ignition timing with a strobe light. "I" is TDC.

Can you give me a link to the thread stating 12 pins?

Knowing the pin count is useful when reassembling the cam chain, though.

What the...did I read this right? Gray actually conceding that there is at least some usefulness to counting pins??? :thinking:

I have the link bookmarked at home. I will send it to ya when I get there later.

Thank you for the information that you provided. I probably made the mistake and was looking at the valve adjustments for the 250f

What the...did I read this right? Gray actually conceding that there is at least some usefulness to counting pins??? :thinking:
Please do not attempt to annoy, vex, anger, agitate, irritate, exasperate, irk, gall, pique, bother, put out, antagonize, get to, ruffle, nettle, aggravate, peeve, hassle, miff, rile, needle, frost, bug, tee off, tick off, piss off, burn up, wind up, run down, bullyrag, or rankle the moderator. :smirk:

It can be useful as an assembly aid, yes, but timing the cams with it without referencing the crank is a HUGE mistake.

Not too far off subject but does it really matter if the engine is at TDC when measuring v-clearance? I usually just put the the cam lobe peak 180 from the surface of the bucket and measure. Is this wrong?

Not too far off subject but does it really matter if the engine is at TDC when measuring v-clearance? I usually just put the the cam lobe peak 180 from the surface of the bucket and measure. Is this wrong?

There's nothing wrong with that as as long as you only only check the valves under the lobe pointing up. The advantage to adjusting at or near TDC/compression is that you can check them all. You know that you don't need to look at the crank to do this. If you roll the engine around to where the cam timing marks are aligned (or close to it), that's close enough.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now