WR426 2001 timing

Hi guys looking for advice on setting cams etc on wr426 2001 - I done heaps of YZ 450's but never an old 426 is the process the same just find the I mark and line up the the cam dots to the head or is there a different process with the WR426 - secondly I noticed when taking a look at this old girl the I mark does not give exact TDC when you probe the cylinder ?? is this correct or has the fly wheel sheared ?? any advice would be appreciated never worked on WR426 need an expert cheers

Yep process is the same, set it to tdc and line up cams punch marks. Mine don't align aswell, I even thought it was because of stretched cam chain so I changed the cam chain. It was stretched indeed, but with new cam chain the marks aligned identicaly, so guess it should be that way. Here is picture of my camshafts with crank set at tdc


And be sure that the marks are shifted clockwize, or else your intakes will have bad time kissing piston, you wont like that metallic sound trust me :cheers:

Hitman, Your exhaust looks off by one tooth to me. Or is it simply an allusion? I also count only 12 cam chain "pins" between the upper timing marks. I don't have my manual in front of me, but going by memory, I think yours is off. You might want to check the search function to verify. Maniac

Thanks guys thats how I assumed it to be but one point of confusion left for me regarding timing this old beast is the I mark on fly wheel, if I set it in position the piston is not at TDC when I probe it? if I set the piston by probing the I mark is about 10mm out - if I set to I mark the piston is definitely on the way down is this normal on WR426 . fact is I have set both by piston at TDC and with ignoring the piston being down a little and just trusted the I mark but either way it would not fire truth is I just want to confirm timing is correct so I can move on and find other reasons for no start - (fuel, jets,spark etc) any ideas or advice greatly appreciated

regards Jamie

Hi Hitman I posted further question about I mark not giving exact TDC on piston but also your comment "make sure marks are shifted clockwise or valve kiss" could you elaborate on this when you get a chance what did you mean

Jamie, When you use a dial indicator probe in the sparkplug hole, the end of the probe might be falling into one of the "cut-out's" on the piston face for the valve clearances. As for the differences between 426 & 450 timing, there both the same. I doubt that the flywheel has moved, but anything is possible. The factory marks could have definately been more accurately applied, that's for sure!!! Maniac

Cheers for the response its a good point but upon doing and doing again I still getting same result. I keeping the probe completely vertical and supporting it to avoid any mis reading - but the result is its out by alot more than any cut out of the piston. You actually can only just see or actually looking straight on at the inspection hole cannot see the (H or the I) mark if I use probe to TDC the piston? your probably more familular than me with marks on fly wheel on this bike, it may mean something if I mention probing TDC lines up more inline with the circle (O) mark on the fly wheel rather than the (I) mark which is at a guess without measuring about 10 - 20 mm out I thinking this would be way more out than any false reading I could get from probing TDC

Just for my own sanity I also side by side tonight went through the exact same process of probing TDC on my 06 YZ450 without even opening the timing plug hole to view I probe set to what should be TDC then opened inspection hole to confirm (I) mark is correct and thank god to my sanity is was bang on correct - I know this fact doesn't prove anything just wanted some confidence I was probing TDC reasonably well as I am relying on this method for this WR426

The bad news is though no matter how I set timing which trust me I have tried every way set to I mark set by probing tdc I even set half way in the middle of I mark reading and probing (thought I would split the difference) I have set cam marks inline with head showing 13 pins between the dots I tried set the cams as YZ 12pins between the dots with just the exhaust cam back one tooth and I barley even get a backfire out of it at any setting so I figure this beast probably has bigger issues than just timing but until I confirm it is actually set correct timing I can't move on to other issues

cheers for the help so far if any more thoughts or advice come into you head please reply open to anything at the moment regards Jamie

Hey maniac, No, the camshafts are aligned right relatively to each other, if I turn the crankshaft a bit, the punch marks on both camshafts get horizontally, and there are 13 pins between top dots in that picture actually. Btw, that was what I thought when I looked at the camshafts, so I rotated both of camshafts 1 tooth counterclockwise, so that the left punch marks on both camshafts were slightly below the horizontal line, and that was when I got my valve/piston hitting. I was able to rotate the crankshaft with kickstarter and the bike was starting like a champ, but it had very very loud metallic clanking noise. I spent 2 days on figuring out what I did wrong and finally found the camshafts being offset by 1 tooth. I guess the interference between piston and valve was minimal coz I was able to crank the engine smoothly, so guess there was minimal damage done aswell, It's Yamaha, ye know :thumbsup:

Jamie, your method of finding TDC sounds OK to me, my I mark is also about 10-15mm off, so guess thats just manufacturing defect for 2001 426s. And as I said, even with timing off by 1 tooth and intake valve hitting piston, my bike was starting on the first kick, so I guess your problem is something else.

And one thing about ruling out fueling problems from your bike: Twist the throttle so that accelerator squirts fuel down into throat of motor, that is enough for it to start and run for a second so if you can start the bike after playing with throttle, the problem definitely is your carby :thumbsup:

Hitman, Your exhaust looks off by one tooth to me. Or is it simply an allusion? I also count only 12 cam chain "pins" between the upper timing marks. I don't have my manual in front of me, but going by memory, I think yours is off. You might want to check the search function to verify. Maniac

The exhaust cam is sat in that position for YZ timing if it is back 1 tooth it will be set at WR timing so for best results with still great reliability yz timing as 'hitmans' setting are, are perfect...

Also i have always found if my wr isnt warm i have to use the choke or the hot start, just throttling a squirt in the bore when theres problems isnt ever enough if you want to be sure the engine runs and recon its the ful/carb or just wonder if its sparking just sprat a little brake cleaner in the airbox...

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