How to check the middle gear needle bearing

1982 Maxim 750.
What should I look for or listen for when checking the middle gear needle bearing? I know how to check roller bearings but this one is a bit strange.

 

Bump.

 

According to Haynes this assembly should last throughout the life of the motorcycle without the need for overhaul or component replacement. They are roller bearings on the schematic. If they rotate with no play roughness they are fine.

 

Sorry I don't think I was very clear.

I am referring to number 28. I cant really get a good position on it to check if it rotates smoothly like I can with roller bearings. The cage that the bearings sit in is slightly flexible like it is made to fit more than one size diameter shaft. I can rotate it with 29 sitting in the case and I can hear some noise from it but I don't know if that's bad or not. I know with roller bearings when they are unoiled you will hear some noise but it will be a continuous smooth noise. I'll try cleaning it again later today and soaking in oil and try it again.

 

They use needle roller bearings in two stroke engines because they do not need a lot of lubrication. The rollers do move a little. They also use them on vehicle propeller shafts. Post a video of the noise if you can. What mileage has your Yamaha done?

 

Well If I go by the tach that was on the bike when I picked it up then 9k miles. If I go by the tach that was in the parts box that came with the bike then around 20k miles. Yeah, I'll try to get a video of it tonight.

 

Here it is without oil:

Here it is with oil:


The grinding noise on the video with oil I haven't heard till now.