Flex 3401 breakdown repair

[Motogoon]

Hey guys, Iv searched for days and can not find any info on fully breaking down the 3401. I have one with a broken drive shaft, the part the backing plate screws onto. This is the second time it has just fallen out. Had it repaired by a detailer who was also a flex dealer and repair shop. Didn’t last long till it dropped out again. Figured I would try and repair it since I can buy all the parts. It truly doesn’t seem difficult but I can not separate the main drive unit. Iv gotten the first lock ring off but the first bearing you see is not popping out. I feel like it’s the only way to move deeper into the disassembly as Iv looked the unit over and over and see no other way. Does this bearing just pop out to reveal another small lock ring? How is there zero write ups or videos on fully repairing these? Iv only seen brush replacement videos. Any tips or help or the tool I would need to get that bearing out would be amazing.

I did get the lock ring below the counterweight off but that didn’t seem to free anything up.

 

[Motogoon]

Well hopefully this helps the next person in this situation. After many hours of playing with this I finally managed to separate everything. If I understood tool repair I could have done a cleaner disassembly but it wasn’t too bad. I did nick a few spots using a flathead to separate but those parts were already damaged so wasn’t too worried. It truly is as easy as it seems, and if the parts aren’t separating it’s because they are seized. Which they should be to some extent since they are probably pressed together. A little PB blaster and time allowed me to get everything apart.

The failure point is what’s most confusing. The largest piece in the photos I believe is called the Centric shaft. The bearing that sits inside seems to have blown out on one side. The drive shaft sits inside of this. I’m not sure or if that bearing is even removable. The parts is $89.

Priced out to a little over $100 for a new Centric shaft, drive shaft, bearings and brushes while I’m in there so may just keep this as a spare parts machine. You can find a lightly used 3401 for $200 so I feel like it’s not even worth fixing. If anyone knows how to remove that inner needle bearing that has failed please let me know!

 

[SNP209]

You can get a similar polisher from harbor freight under the hercules brand for $120. Sometimes cheaper if there is a sale. I would just go that route personally.

 

[Motogoon]

You can get a similar polisher from harbor freight under the hercules brand for $120. Sometimes cheaper if there is a sale. I would just go that route personally.

I’m aware of the other polishers. Iv had 3 3401 polishers for the past 15 years. I just never got around to repairing this one after the first repair. I fully trust the 3401 to never leave me stranded where as I can’t say the same for the harbor freight polishers after certain amount of time

 

[Setec Astronomy]

If anyone knows how to remove that inner needle bearing that has failed please let me know!

They make (expanding) blind hole bearing pullers but there isn't much to grab on from the looks of that, and the housing has to have enough clearance for it. Those pullers are usually for ball bearings where you can pull on the inner race. Do they sell the whole part with the bearing installed? Or the parts individually?

The other thing is if that housing is aluminum you may be able to heat it up and bang the open end on a block of wood to knock the bearing out. The aluminum will expand more than the steel bearing...that's if that housing is aluminum.

 

[Motogoon]

I actually thought about freezing the parts but totally forgot that step! Thanks for the reminder. I don’t think this bearing will just slide out being the top side is blown out probably making it even harder to remove. They sell the parts separately which is why I’m assuming it comes out. The main unit isn’t bad and is $89. So I’d rather just get the bearing out but seems like a job for a machine shop. Still really confused how the bearing blew out like that. I just remember the pad driveshaft getting sloppy when this machine went down. And then basically fell out of the machine.