WR400F Cam shaft timing?

Well I removed the head cover off my WR400 today to check the valve clearances (A first for me), but I ran into something I'm a little unsure of. While aligning the crank shaft for TDC, I noticed that the intake camshaft punch marks aren't aligned with the head properly. To me it looks as though it's out 1 tooth, but I'm not sure since the engine has been running fine. I've included some pictures of everything. I'd just like to know if I need to shift the intake cam counterclockwise a tooth, or whether it's supposed to be set up like this. I've had the bike for around a year now, and I'm not entirely sure of any mods it has. Again the engine has been running flawlessly just the same. Thanks in advance, Marc :p


Just looking over some other posts, I'm beginning to think that my intake cam has been changed to YZ specs, possibly?

Stretched timinng chain ? mine was stretched out about half a tooth eg it was either a little over or a little under the mark if i moved the cam 1 tooth forward and back. I replaced my chain and it was all good, could be YZ timing as you mention if it is a whole tooth out.

It looks like something is wrong. To switch to YZ timing it is the exhaust cam that is supposed to be retarded and it looks like someone moved the intake instead. I would release the tensioner and move the intake one tooth. If it looks like that made it go too far the other way then that my confirm the streched chain. If that fixes it then this would be a good time to retrard the exhaust cam one tooth and see how the YZ curve feels.

I would agree with Maxtherat. Also probably a good time to replace the cam chain anyway, but it does look like a botched YZ Cam Timing Mod to me. Just my 2c, hope this helps.


Thanks for the replies fellas, I might pull the head cover back off tomorrow and play around with it a bit. I've just been a little unsure of it since the motor has been running rather well. Anyway I'll give the proper YZ timing a shot while I'm at it. That'd be; exhaust cam rotated counterclockwise a tooth?

If you were looking at the cam gear, like your picture, then it would be turned clockwise. The outcome is that the lobe would be pointed higher when at TDC.

When you remove the cam retainer be VERY careful not to drop or loose the 1/2 circle clip that aligns the cam bearing. I have been fortunate to be able to fish it out with a magnet for retreving bolts. Best choice is not to loose it.

You might as weel go ahead and check the valve clearance. You will likely have to remove both cams to adjust the intake anyway.

Thanks guys, you've helped a lot. Just to be on the clear, as I might get stuck into it after work - I'll realign my intake cam by shifting it counterclockwise a tooth, while shifting my exhaust cam one tooth clockwise for YZ timing? Hopefully that'll save me a bit of trouble and I'll see how she goes :p

That is correct. When you are finished, the intake timing mark should line up with the head at TDC on the compression stroke. Then you should count 12 chain pins inbetween the two top timing marks on the two cams. This indicates YZ timing. As old as that bike is however, I would highly recommend replacing the chain at this time. You are already half way there and it is cheap insurance. If the chain breaks, you are going to be in a world of hurt. I think the chain runs around $30 and the flywheel puller is also around $30. Just my 2c, hope this helps.


Thanks Jbrooks, that info saved me quite a bit of trouble. While readjusting my cam shafts for YZ timing, I noticed that there was only 11 pins between the two timing marks. This leads me to believe that my intake cam timing was set up fine to begin with, yet my timing chain must have be stretched. Anyway I moved my intake cam back to the position it was originally in, and set the exhaust cam 12 pins apart like you said. I stuck it all back together and it's running like new, with all the extra "oomph!" I was hoping for. Anyway I'm going to take your advice and stick a new timing chain in it next week; given the state of the stretching, well assuming that's the case then I'm definately due for a new one. Anyway thanks again for all the help, it's been much appreciated :banghead:


Please post a pic of your cams after the changes. I am still no convinced that the chain streching is your problem.

yes, pictures would be nice. I would not have expected it to run very well at all if both cams were out that far. From your original pictures, it looked like the exhaust was timed properly for WR timing and the Intake had been moved one or two teeth CCW. New pictures would be great for anyone doing this work in the future as well. Then they would have before and after pictures. Glad it is running better, let us know how it comes out after the new chain.


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