Exhaust hot cam w/autodecomp.

6 replies to this topic
  • Sylvain

Posted March 06, 2005 - 07:27 PM


I have this weird idea that I (my knee) deserve a break, so I'm thinking about installing a hotcam exhaust side with autodecomp on my wr 426.

I need some info on this. I know the procedure but, what parts do I need to install this autodecomp cam ? Is it just a take off the old cam and put the new one back in ? Should the valve clearance remain the same ? Also what would be a good price to pay for ? any idea ?

Is the hotcam specifically design for the wr ? Will it match the cam gear correctly ? Or is it like a wr 450 2003 cam on a 2002 426 ? Slight misfit with no apparent problem ?

Thanks for all your infos. :)

  • Rattler88

Posted March 06, 2005 - 08:02 PM


Go to the YZ400/YZ426/YZ450 and they have the link that will give you the how too's
and the cam part # that you need I did my 01 426 and it's the reason
that I still own it, you replace the exhaust cam only with the 450
autodecompression cam and it's the best upgrade that you can do
for your bike and your body. :) :)

  • Scotty426

Posted March 12, 2005 - 06:27 AM


I did the hot cam yesterday. The sprocket size is just like the old cam unlike the 450 cam. I think the only real difference is tooth depth and many guys really like the 450 cam. Mine with the hot cam fired right up on assembly. You need to get the plug from Yamaha that covers where the lever went into the head and you have to reshim the exhaust valves. It has a card that says to reshim, get shims .25 mm bigger than whatever is in there(they have marks on them, mine were 170s). I did and lash was perfect at .20mm . It fired right up and kicks easy. Very nice.

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  • Birdie426

Posted March 12, 2005 - 07:26 AM


Scotty's got it nailed. .25 thicker shims put my clearances right back where they were with the stock cam. Gears match perfectly as well. Only one more piece of advice- When checking the valve clearances, I come from the old car school of checking when the cam lobes are pointing straight up from the valves to ensure you really are checking the max clearance (between the minor or base circle of the cam and the valve). When you do that instead of checking at TDC, the autodecompressor pin is already pushing against the l/h exhause valve. I started checking that valve and a .050 in feeler gage was loose in there! I thought "Whiskey-Tango-Foxtrot" as the other valves (I did both intake and exhaust cams) all worked fine. Then I remembered the pin, retracted it using the linkage, and all was well.

  • Sylvain

Posted March 12, 2005 - 07:48 AM


I ordered the yz450 cam for my wr 426 2002 last thursday at 03:30 in the morning, I was working night shift :) . Now I can't wait to have it here.

Thanks for all the infos :)

  • Scotty426

Posted March 12, 2005 - 07:21 PM


Good luck. One less thing to mess with. I had my first ride post-install. Power is great. Great bottom, great mid, great top. No problems on break-in. My directions said your 1st half hour to ride it at moderate pace with changing RPM. I did and she's right as rain.

  • Scotty426

Posted March 18, 2005 - 06:05 AM


My thinking for going hotcam was that when I'm used to the bike. I can get the intake cam and together with the exhaust, get a good performance boost. Also, hotcams has deeper teeth, like the original. Could I get a performance boost by going with both 450 cams? I don't know. Some guys who talk to the forum think the 426 is faster than the 450 from the get go. I love the light kick though and the simplicity of starting drill.


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