wr450... need more bottom end...


10 replies to this topic
  • Just_a_trail_rider

Posted June 24, 2008 - 08:20 AM

#1

After three years, two of them racing, it just may be time for me to do a top end.

I need a little more lowend out of my bike to make it just a bit easier to crawl up and over the rocks. Can I get more low end with just a cam upgrade, or do I need to go big bore.

Who's been down this road?

  • Demo_Slug

Posted June 24, 2008 - 08:32 AM

#2

Don’t know anything about cams or big bore....

You’ve probably already done this but...Have you tried exhaust and sprocket changes?

  • Just_a_trail_rider

Posted June 24, 2008 - 09:10 AM

#3

Yep... I have the correct jetting, exhaust, megabomb header, 13/48 gearing, etc...

Its just that the bike has been ridden hard the past couple of years. But even worse, I tore a hole in the air boot (unknowingly) and have been sucking down major amounts of dust straight into the carb. I completely fried the clutch on Saturday and seriously, seriously abused the engine with little or no coolant while trying to get it over a nasty hill while my clutch was slipping badly.

I've gotten my money's worth out the existing top end and I need to do a tear down and inspect anyways. But when I do that, I might as well do few upgrades.

  • wRrooster

Posted June 24, 2008 - 01:57 PM

#4

The YZ exhaust cam will open up the torque nicely on your WR.
I'd say that this is the best power mod for these bikes, and the cam is only about $100. I did the cam swap a few years ago and love the new low end power/torque. I've found that my exhaust valves are wearing a bit more, but its worth the regular re-shimming for the way the bike runs now.

  • Just_a_trail_rider

Posted June 24, 2008 - 08:46 PM

#5

The YZ exhaust cam will open up the torque nicely on your WR.
I'd say that this is the best power mod for these bikes, and the cam is only about $100. I did the cam swap a few years ago and love the new low end power/torque. I've found that my exhaust valves are wearing a bit more, but its worth the regular re-shimming for the way the bike runs now.


Thanks wrrooster.

Does the yz exhaust cam affect the estart? Will it still start well with one stab of the button?

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  • Fullbore4

Posted June 24, 2008 - 11:45 PM

#6

For some reason of which I'm not technically adept, it does make starting with e-start a bit harder (longer)

  • PBDBLUE

Posted June 25, 2008 - 05:22 AM

#7

For some reason of which I'm not technically adept, it does make starting with e-start a bit harder (longer)


Might be because the jetting needs to be tweaked. In my experience if the jetting is off (pilot/needle) the bike will have more difficulty firing with the estart but will start fine with the kicker. That said I have two WR450's - one with a WR cam and the other with a YZ cam. Both estart no problem most of the time. If it's really cold in the morning both struggle a bit but I can't say one more than the other. Anyway the YZ cam and a free flowing exhaust will make a huge difference.

  • Just_a_trail_rider

Posted June 25, 2008 - 05:50 AM

#8

Thanks guys... just to be sure... I will get a 2005 yz exhaust cam for my 2005 wr, right?

  • Fullbore4

Posted June 25, 2008 - 05:38 PM

#9

Part numbers are a little different ie. 06 has a -10 instead of -00 but that may have to do with autodecompression......correct me if I'm wrong.....but I would inquire further to see if the 06 will work if that is the case.

  • Jwar1r1t3

Posted June 25, 2008 - 06:47 PM

#10

Correct me if I'm wrong but i thought I heard that you can get YZ timing simply by advancing the cam sprocket on the chain by 1 tooth. :thumbsup:

  • VB_Racing

Posted June 29, 2008 - 05:23 AM

#11

The one tooth trick only works on the 400's and 426's before they went to auto decompression. With the 450's you have to change the cam.



Dave




 
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