Decompression Cam

5 replies to this topic
  • calvin71

Posted August 21, 2005 - 09:14 PM


I'm looking for the right decompression cam for my 2000 426 YZF. Which should I be looking for, the exhaust cam or the intake cam? Also, will this cam enable me to start up without using the decompression lever? Finallly, any idea on the difficulty rating (1-10, 10 being extremely difficult) on this install would be much appreciated.

  • Birdie426

Posted August 21, 2005 - 09:32 PM


You want the exhaust cam. Either the stock Yamaha 450 or a hot cams cam. There's a whole bunch of info on the differences in sprocket tooth pitch and implications on a stickie at the beginning of the forum. Difficulty is about a 4 if you have the right tools (feeler gage and in-lb torque wrench). Took me about an hour and a half, not coounting all the time dorking around trying to find the right shims at the various shops around town.

  • Vetmxrider

Posted August 22, 2005 - 05:00 PM


I did the 450 cam swap in my 2002 YZ426 6-7 months ago and it was very easy to complete and I had never even checked my valves. Make sure you use a torque wrench that measures in inch pounds NOT foot pounds to torque the four bolts that hold the cam caps. After you check your valves with the new cam you will need to go to your dealer to buy/order the correct shims to give you the right clearance. Don't wait, do it and enjoy!
Good luck.

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  • calvin71

Posted August 22, 2005 - 09:57 PM


Don't want to sound stupid here :D but what do you mean I'll have to get the shims after I check my valves wiith the new cam?

Also, did this help with the start up of your bike? I'm trying to figure out if I'll be able to start up without the use of the compression lever.

  • grayracer513

Posted August 22, 2005 - 10:14 PM


See the valve adjustment procedure in your manual. Camshafts vary enough that you will likely find the valve clearance out of spec with the new cam.

And yes, although the carb will still be somewhat cranky, you will no longer have a use for the decomp lever.

  • 4Stroke4Life

Posted August 23, 2005 - 08:14 AM


whats the deal with the decompression lever anyway. i bought a 99' YZ400F about 15 months ago. it had the 450 cam in it and starting was a breeze. 2 weeks ago, i found a crack in my case. took it to the shop and my journals were all jacked up. ruined probably. luckily a guy was selling his 01' WR426 engine, w/ new clutch, oil seals, gaskets and piston, w/ a brand new head. so i swooped that up for 700$. i had to dig up my decompression lever and parts to re-install. but have never used it. how does it take role in starting and when do you use it??? :D :D

oh, and what about the YZ timing. what does this do for power??

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