decompression mod on 98 yz400f


7 replies to this topic
  • honda0071

Posted January 07, 2008 - 06:26 PM

#1

i learned not that long ago about the decompression mod with the new exhaust cam from an '03 yz450.... does it work? what do i need exactly i mean everything... i gunna do it i just need to know at i need to get it done.. what special tools do i need as well please any help greatly appreciated..

  • Smokeslider

Posted January 07, 2008 - 06:33 PM

#2

I'm not sure but looking at HOTCAMS, they have different cams for the two models. Both have the same valve lashes but lobe centers and durations are different. So, I guess IMHO I would be very careful about doing this until your sure the parts will fit. Good Luck.

  • Vetmxrider

Posted January 07, 2008 - 07:26 PM

#3

i learned not that long ago about the decompression mod with the new exhaust cam from an '03 yz450.... does it work? what do i need exactly i mean everything... i gunna do it i just need to know at i need to get it done.. what special tools do i need as well please any help greatly appreciated..



This mod works great with no regrets. Don’t wait, just do it and enjoy your bike even more! You will need a torque wrench that reads in inch pounds (NOT FOOT LBS.) to torque the cam cap bolts back to specification. Just do a search under cam swap for lots of useful information.

  • jmalkames

Posted January 07, 2008 - 07:29 PM

#4

i did it on my 98 and it was the best mod i have done to any motorcycle. email me and i can send you the instructions, unless someone wants to post a picture for me.

malkames@sbcglobal.net

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jmalkames

Posted January 07, 2008 - 07:35 PM

#5

nevermind here it is.

http://www.thumperta...078#post3706078

  • honda0071

Posted January 07, 2008 - 07:54 PM

#6

where do i get a set of metric feelers and an inch lb torque wrench?

  • Birdy426

Posted January 07, 2008 - 08:36 PM

#7

The inch pound torque wrench is kinda hard to find...it also should be 1/4 inch drive as a 3/8 or 1/2 inch drive will start at torque values far greater than what the cam cap bolts should be torqued to. Sears can order one but very few sears stores actually stock them http://www.sears.com...8&gobutton.y=10

Harbor freight can hook you up with one cheap, but you get what you pay for. Most auto parts stores can also probably order one from Proto, Husky, or Snap On. As far as metric feeler gages, most feeler gages have both the metric and SAE thicknesses etched on them. To make the job easier, get Motio Pro Tappet feeler gages. They are narrow enough to get into the center intake valve without having to trim the blade (which can lead to inaccurate readings due to burrs onthe trim). You will also need shims, but you won't know what thickness until you install the new cam and measure the resultant clearances. If your old shims are worn, you may also need a pair of dial calipers or a micrometer to measure the thickness...

Follow the book closely and you shouldn't have any problems.

  • grayracer513

Posted January 07, 2008 - 09:26 PM

#8

On the torque wrench, look for a flex beam type from a Snap-On tool truck, or a good auto parts house. They will be far less expensive that a dial type or a clicker.





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