1972 WR 250 Oil Question

I am new to this bike. Changing the seals, and forks, and oil. I am looking for how much to put in each fork, What kinda oil? I heard 40wt is what a lot of the older bikes used.
In the motor what oil wt should i use? I read in another thread one guy said 10w-30 or 10w-40 works. or should i use a solid weight of like 30 or 40? Thanks

I've never heard of anyone here in the vintage section ever mention using anything close to 40wt in forks. More like 10-20 wt. I run 15wt Motorex in my 40mm forks, seems to work okay for my me at 235 lbs

Everyone had heir opinions on oil, but I'm currently using Honda wet clutch specific anti-foaming oil, I think it is 30wt, if I was at home I'd check.

I the manual i just saw said 20wt in the forks, but i recently got new race tech springs, but I think I am gonna still put in the 20wt. and for the motor oil it says SAE 20-50 depending on weather. So I am gonna run 30wt.
Sound ok?

The forks can use 10, 20 or 30wt, depending on temperature, riders weight and how hard you ride it. I would recommend trying the 20wt first, but try to find non detergent oil. Back in the day, non detergent oil exhibited less foaming. Not sure if this is still true today, however the typical modern motor oils have not only detergent, but lots of other additives you don't need in a fork oil. Most of the specific fork oils today are too thin for these old damper rod forks. When I was younger we ran auto trans fluid in the forks, but now that I am at 185 lbs., I find I need something with more viscosity. I presently have 20wt. in my forks. 200cc or 200ml (same thing) in each leg. I have not tried multi grade oils (10w30, etc.) The four speed transmissions called for 30wt. non detergent, not sure on the 5 speed, I'll check the manual and see if I can find out. I run type F auto transmission fluid in my four speed tranny and it is ridden hard in vintage racing. Clutch seems to grip better than with 30wt oil. You'll find many modern dirt bike riders who also run type F. If you choose to do so, be sure it is type F. Dexron and other ATF's have friction modifiers that can make your clutch slip. My opinions only, hope it is of help to you.

You may also want to consider how much oil you put in the forks.
I'm not sure if the factory was into tuning the suspension back in the day and I think the factory specified amount of oil, was probably just enough to cover the damping rods?
However, there is an "air space" created in the fork tube, it's the oil level to the top of the tube.
By increasing the amount of oil, your reducing the air space which will cause the pressure in the air space to rise faster, as the fork is compressed.
Most folks measure the oil level with the forks fully compressed and the springs out. By changing the oil level height in the fork, you have another suspension tuning option.
Adjusting the oil height in the forks is mostly only noticed, as the forks get close to bottoming.
But it will make a difference. I would start with 7" from the top and add oil to reduce bottoming.
Generally in 1" increments.