Fun with Timing
Posted April 04, 2007 - 07:34 PM
Began a valve inspection today on my 98 WR400. It's the first time I've done it since I've owned it. (I don't ride all that much, and it's all trails). The guy I bought it from informed me of some free mods that were performed, like the YZ timing. Cool, I thought - no big deal.
That brings me back to my valve inspection. When I set the motor to TDC, nothing looks right. Look at these pictures and see for yourselves:
http://photos.yahoo.com/big_theo --> Then click on the Yamaha WR400 Album
Look where the 12:00 puches are - they're way off right? I've looked at a lot of info regarding the YZ timing mod (thumpertalk, thumperfaq), and I think the intake cam should look like stock. Punches at 9:00, 12:00, and 3:00. Am I wrong? The exhaust cam modded should have 12:00 punch pointing closer to 1:00, with 12 chain pins between the 12:00 punches. This shows 13 pins... Furthermore, look at the cam lobes! This is not the position that they need to be in to perform a valve inspection right?
Which brings another question... If one does the YZ timing mod, won't that affect the TDC setting for the lobes to be in the proper position? FWIW, I did go a little past TDC to get the cam lobes to where the manual said they should be and inspected the valves. Good news is, they're all in spec (provided the point that I measured from is correct). They are all on the short range, but in spec nonetheless.
So what's up? Is is a wonder that the motor even ran? I have not adjusted anything yet. The plan is to get to the correct YZ timing mod setting. Wanted to get a take from the 'experts' first!
Thanks in advance all!
1998 WR400F (shouldn't be giving me fits)
2003 Ducati ST4S (gives me fits all the time)
Posted April 04, 2007 - 09:11 PM
The intake cam timing has been retarded one tooth and the exhaust cam looks to be set for YZ timing. Advance the intake cam one tooth and you should be okay. The bike will run like it is, but is far from nominal.
Once you get intake cam set correctly, rotate the crank a few times and recheck the valve clearance with the crank set exactly to TDC. Also make sure the cam chain is under firm tension and the cam caps are torqued to spec too when you check the clearances.
Posted April 05, 2007 - 04:43 AM
That's kind of what I thought. In order to get the correct YZ timing mod, would I not also need to go to 12 chain pins instead of the 13?
Thanks for the help,
Posted April 05, 2007 - 05:56 AM
Posted April 05, 2007 - 07:34 AM
Like nchampion, the auto compression release cam is an good upgrade. I've had excellent results with the one Hotcams makes.
Posted April 05, 2007 - 08:24 AM
Are you sure you're on TDC? Looks like both cams are off. Sometimes the crank will move after you set it at TDC. Do a search on TT for good pics on how to do the cam timimg. (I'll try to find a link) It should not look anything like what you have.
It's at TDC. The | after the H in the window. I think once I advance the intake cam it will look better, like scott_h says.
About my valve adjustment question: Am I correct about the proper setting? I used the lobe position as a reference instead of TDC, because I think that once you modify the stock timing, TDC does not put the lobes in the correct position to inspect the valves? Is that right?
Thanks for the input guys!
Posted April 05, 2007 - 08:49 AM