03' yz450f with wr 5spd and hole in crankcase

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.

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.

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

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

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.

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

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