03' yz450f with wr 5spd and hole in crankcase

5 replies to this topic
  • city slicker

Posted October 20, 2010 - 07:13 PM


I have an 03' yz450 4spd and like it alot exept in the tight stuff, then one weekend at croom ohv park it spit the kick start gear out the back of the crankcase. So I stalled on the build until I found a set of trans gears,shift forks and the shift drum from an 06' wr450 and with wiesco piston, con rod,new cyl,port and valve grind plus some used cases from ebay I was on my way to a woods worthy 5spd and with a big weekend coming up it was crunch time getting it together. I did get it done and the lower 1st really lets me crawl up things I couldnt before and the higher 5th carry's alot more speed. The only problem is a small hole about 1/8th in is drilled on the right side crankcase housing right below the base gasket and cylinder which blows crankcase gases and oil vapor on the head pipe. Is this a wr side case that has this hole or did someone drill this for something or another. any help is appreciated thanks.

  • grayracer513

Posted October 21, 2010 - 07:04 AM


Can you elaborate on where exactly this hole is? Is it in the right crankcase half itself, or the right crankcase cover that houses the water pump, etc? Post a picture?

Doesn't sound like anything I'm familiar with on that model.

  • jayh300

Posted October 21, 2010 - 07:34 AM


cant think of that either on my 06 wr... just looked thru all my pics of it and i have no pics of the rh side of motor...(except one where it is packed full of mud)
can take and post tonight if needed for reference

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

Posted October 21, 2010 - 02:40 PM


yes its on the right crankcase half itself just under the cylinder/base gasket thanks for the reply

  • grayracer513

Posted October 21, 2010 - 02:44 PM


If this crankcase had all the correct oiling fittings for the feed and return oil lines, then that hole does not belong there as far as I know.

  • city slicker

Posted October 21, 2010 - 03:10 PM


I was afraid of that! well I guess I'm tapping and plugging it. thanks alot for your help.

Related Content


Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.