Disassemble Canon 85mm f1.8 or 100mm f2

I have a Canon 100 f2 USM lens that I want to disassemble to clean the inside of the rear element. I found the parts diagram, which is some help.
http://www.f20c.com …tslist/EF%20100​%202.0.PDF

I am able to get most of the elements taken apart, but I can't seem to get the USM motor off, or get the rear element and circuit board removed.

Does anyone know how to take the rear element out, or have disassembly instructions? Since the 85 1.8 is mechanically very similar and much more popular, any instructions for that lens would probably be helpful. "Send it to Canon" or "you'll ruin your lens" are not helpful responses, but any other advice would be appreciated. Thanks.

the rear element is threaded in. If you look closely, you'll see two holes on the opposite sides of the rear glass element. You will need a lens caliper to twist the holes counter clockwise to remove the rear element.

this pretty much applies to all canon lenses.

http://www.ebay.com …em53ec734849#ht​_500wt_966

you'll need a tool similar to this.

Got it, thanks!

And while you didn't want to hear "send it to Canon", I would advise you to read a recent thread from a member who took apart his 300 f4L and realized getting it apart is only half the battle. His story ended with sending it to Canon. Good luck.

mileslong24 wrote in post #14513981
And while you didn't want to hear "send it to Canon", I would advise you to read a recent thread from a member who took apart his 300 f4L and realized getting it apart is only half the battle. His story ended with sending it to Canon. Good luck.

the design of a 85mm 1.8 or 100mm f/2 is substantially different then any of the professional white telephoto lenses. These are easier to disassemble and have less chance of error since neither of the OP's lenses have a sensitive component (IS mechanism) which is suspended by neodymium magnets.

One of the lenses you don't want to disassemble without extreme precautions would be the canon 35mm f/2 as there is a ribbon cable that is soldered to the PCB.

good luck on the tear down.