I just bought 2 2001 yamaha Blasters , one appaers to be modded inside and out ... the other one appears from sight and driving to be stock except FMF exhaust and nerf bars. I want to change crank oil ?? But Im getting a lot of different oppinions about oils (transmission fluid, 10-30 motor oil, synthetic motor oil ,and some product called bell-ray, and a couple others ) Yamaha says yamalube-4..???????? The stock blaster when I bought it started fine and ran great got it out on paved road and it screamed threw all 6 gears but before taking off I had it ideling in nutrual pulled clutch in and popped it in first and I heard a faint whinning noise but went ahead and took off and when I got back from run itt did not appaer to make the whinning noise any more and when i asked the seller about the noise I had heard he told me that he had been running transmission fluid in crank found out he was suposed to be using motor oil and changed the fluid to motor oil then he noticed a faint whinning noise after so I talked him down on the price $200.00 and bought it , hopeing he was not lieing and being truthful Im telling yall this hopeing somebody will tell me if the fluid change is related to cold start whinning or sign of something else and of course back to original question about what is the best oil to use ??????? (HELP PLEASE) sorry for rambling on !!!

yes pretty much all of those will work. If you use tranny oil use TYPE F. Dexron has friction modifiers that are not good for your clutch. 10-30 motor oil is the same viscosity as 80w90 gear oil...they are just measured on different scales. both work. I use Rotella T. The diesel truck oil. In my RM85's, KTM65's, KX250F even my CT70. I did use ATF Type F for years without a problem. The main thing is change often. I found customers that I reccomended using ATF to changed their oil much more often than people using expensive $10/quart fancy stuff. Guess which is better for the engine? If you never change it you will run low. Every time you ride you will lose a slight amount out the vent. People that use cheapie oil but change every ride end up with a better bike.
And oh you can build totally bad A$$....chetah cylinders and heads. big bore stroker. Gimme a shout if you ever blow it up. They can be LOTS of FUN!

I'd bet the bearing the clutch basket rides on is the source of the cold noise. Not due to the trans oil but probably due to low oil.

Ramble right back at ya.