YZ/WR exhaust cam timing project has me scratching my head. Help...

I pulled the valve cover off my 2nd owner low hour 02 WR426 and found that the exhaust cam was 1 tooth COUNTERclockwise from 9, 12 and 3. I put the intake cam at 9,12 and 3 using the edges of the head as a visual and when the intake cam 9 and 3 (o clock) dots are even with the edge of the head, the exhaust cam was at approx 8, 11 and 2. I ended up re-assembling it 2 tooth clockwise from where it was and am now at 1 (o clock) per the instructions in the TT faq section.

The previous owner had done all of the "free" mods but Im wondering now if he attempted the YZ cam timing and went the wrong way? The bike ran really good but wasnt overly impressive in the power dept. It had decent low end but flamed out on top and just made a bunch of noise. I cant get in touch with the original owner to ask him so Im wondering if its even feasible for it to run decent 1 tooth counterclockwise from the factory WRF cam timing. If so, yippie cuz I cant wait to ride it. If not, I dont want to smack a valve or burn it down, etc. Another possibility is that he mistakingly rotated the INTAKE cam 1 tooth clockwise so it appears that the exhaust is counterclockwise 1 tooth. Also, my flywheel absolutely has no "I" timing mark. The only tiny dash visible has the cams everywhere but 9, 12 and 3. Any input here is greatly appreciatted!!!

Edited by un chained

Your flywheel does have the "I" mark somewhere! Just be aware that it will only show up in the correct location when the engine is on compression, or in other words, every other time the piston is at TDC. The "I" mark comes right after the extended looking "H" ignition timing mark. Lets start with finding that timing mark first. Maniac

Ok, I guess being a 4 stroke, I could have been looking when it wasn't on the compression stroke. I do have the H then I but whenever it was on that, the cams were not anywhere near 9,12 and 3. I'll check again though because that will def answer my own question if the intake cam is indeed 1 tooth clockwise 1 tooth from factory. Thanks,,,,

Ok, I took the cover back off and put the timing mark right on the "I" and the intake cam is at what appears to be slightly clockwise past 9, 12 and 3. i did not move the intake cam, again, I moved the exhaust 2 teeth clockwise. With the flywheel lined up with the mark on the cover, is this where I should expect the intake cam to be or did the previous owner move the wrong cam? thanks!




the exhaust cam needs to go 1 tooth back (COUNTERclockwise) then you got the YZ timing, as it is on the pics its YZ +1 tooth. 2 tooths back you are back at WR timing..

Edited by RasmusDK

Ok, glad I double checked it before I took it for a rip. Thanks,,,,

Also, I see that the grey wire the previous owner cut was not in a 6 pin connector. What he cut was a grey wire going to the cdi but with 1 other wire in a 2 pin connector. Is that the correct grey wire for the 02 426?

I corrected the exhaust cam back counterclockwise 1 tooth (from the above pic) and re-assembled last night. Bike wouldn’t idle with previous idle setting and was erratic once turned up so re-jetting and tuning appears to be a must. I also added a new GYTR stepped head pipe while it was apart as well. Overall, the top end is significantly stronger and she revs much higher now. Low end and mid-range feels compromised now compared to the stock WR timing and head pipe. Will dial in the jetting next and possibly pursue a better muffler than the uncorked stock WR unit. Overall, my first impression of the power increase with the YZ timing isn’t like WOW!!

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