[henrylr]

I bought an AKAI 4000DS MK-II new in the 1970s and it worked well for many years. but hasn't been used in the last 5 years. I tried it yesterday and the take-up reel wouldn't rotate. I viewed some youtubes showing AKAI reel to reel repairs and learned that worn idler wheels can be the cause. I took the cover off and found the rubber is hardened and worn so I bought new wheels. Some youtubes showed idler wheels being replaced but didn't show or give any info on lubrication. My Akai show no traces of oil, only a few small dabs of grease where moving levers rub against each other. Regarding the idler wheels, one has a nylon bushing, and one has a brass bushing and both spin on stationary steel spindles. My question is would the idler wheel with the nylon bushing not need lubrication and the one with the brass bushing need lubrication? Photos of idler wheel system of two 4000DS MK-IIs are the same but the idler wheels are different...maybe Akai changed wheel design over time.

[FullRangeMan]

IMO it need some lubrication as its a moving part, I would use the white silicone grease, the same used in CD/DVD transports.
Oil will attract dust.

[henrylr]

Thanks for the info. Another concern I had is that the take-up reel slips and has very little torque. I've read that cutting the spring shorter will increase the force of the idler wheel against the take-up reel, fixing that problem. But I didn't want to cut the spring, so I came up with an alternative where I could increase the torque by twisting the spring. I reconnected one end of the spring to the idler wheel arm, pulled the other end through the spring attachment opening in the frame, twisted the spring attachment hook two turns and locked it in place.  Now there is plenty of torque and the take-up reel now works great.