Paging DR J.Dean

I have just changed the cam timing on my '99wr to yz spec, and decided to take your advice and install an EKP needle instead of the yz400 needle. If its the needle or just the timing I am very impressed with the results, although I only rode the bike for 45 mins, due to shearing all the teeth off my front sprocket I did happen to notice that the bike 'popped and cracked' when I backed-off. A friend told me that it seemed to run lean just off idle, as I dont know very much about the black art of jetting I would greatly aprieciate your opinion on the matter.

needle ekp clip on 3rd groove

mainjet 168

pilot #45


mainly ridden under 1000m above sea level

15-50 gearing


How on this earth did you shear the teeth off of your front sprocket?



99 WR, all YZ mods, de-octopused, OEM YZ tank and IMS seat, jetting by Clark, got forked by Pro Action, WAITING IMPATIENTLY FOR MOAB!!


What was your pilot screw set at? (on the bottom of the float bowl where you can't see it) The "ballpark setting" with the 45 was 2 - 2 1/2 turns out.

James Dean

James I'm not exactly sure what the pilot screw was set at as my mate set it for me after I'd done the mods, but if you think the rest of the settings are all right I'll check it out.

Thats the 64 million dollar question, Kevin. All I know is that the chain and sprockets all looked good the day before, the chain was lubed and adjusted correctly. I only noticed that horrid noise of chain grating over metal as I was riding trough some really tight stuff. I can't complain though as its the original chain and sprocket and I would have done at least 4000k's on it, I'm just spewin' that I didn't have a spare sprocket with me as it happened an hour into the ride and the tracks were BOOMIN!

My Brother sheared his front sprocket teeth off due to the chain being too tight. As the swingarm goes through it's arc, the distance becomes longer between the countershaft and rear sprocket. Now this was a LONG time ago on a Suzuki TS 185. Back then we didn't have the nice swingarm pads, and the countershat was not located near the swingarm pivot like on todays bikes.

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