81 Yamaha IT 175 Fuel ratio, spark plug info

So I purchased a really nice 1981 Yamaha IT 175 for my collection and have a couple of questions (always been a 4-stroke owner ;>).

What is the proper fuel-oil mix ratio for this machine, 40:1, 50:1 ?

What is the proper spark plug, I read online to use a NGK B9EV

I also need a idle screw and lock nut for the Mikuni carb. I believe its a VM34 model but not sure . The idle screw is on the left side, air mixture is on the right . Idle screw should have a lock nut . Where can I find a new one of these ?

Planning on doing some AHRMA racing with it....oh yeah and it has a street legal title too....yikes

Thanks for any help !

32:1 is your friend but IDK about spark plugs on that machine.

I had a 80 175 :lol: can you post some pics of you 81..

The B9 will do fine. You could also go up a heat range to a B8 and be OK too. The original plug is actually a Champion plug. Go figure.

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