Results 1 to 7 of 7
  1. #1
    CB750 Member flatpick13's Avatar
    Join Date
    Oct 2020
    Location
    Texas
    Posts
    13

    Remove rotor to split crank case?

    Iím trying to split the crank case on a 1980 CB750F, it seems like the rotor is catching lips on the crank case and keeping me from pulling the bottom off. Do I need to remove the rotor to split the case on DOHCs or am I doing something wrong?

  2. #2
    CB750 Guru amc49's Avatar
    Join Date
    Sep 2015
    Location
    Fort Worth TX.
    Posts
    3,386
    Rotor does indeed have to remove, the crankcase there goes slightly inside the rotor where it has a recess on the back of it. On all early DOHC except possibly the 1100 because that rotor is different and narrower back there. The smaller engines need the extra flywheel weight of the thicker part.

    Dangerous to remove rotor with cases loose, the violence of it may do case-to-case damage. If I were you I would bolt them back up solid, not to torque and not all bolts, just enough to firmly hold the cases together. Say crankshaft area bolts for the mains.

    A rear axle to rear wheel makes an excellent puller.

  3. #3
    CB750 Member flatpick13's Avatar
    Join Date
    Oct 2020
    Location
    Texas
    Posts
    13
    Ok, thanks, will do! I already ordered a pulled, I figured Iíd have to take it off and couldnít think of anything else holding the case together

  4. #4
    CB750 Guru amc49's Avatar
    Join Date
    Sep 2015
    Location
    Fort Worth TX.
    Posts
    3,386
    The axle is better as you have a handle to hold the part when it suddenly springs off crank like they usually do. Whatever 'puller' you use gets run up tight to crank and then a sharp rap on the end with a steel hammer. Every time you hit it then you adjust the puller to again be dead tight to the crank, if not it will never come loose and you yank crank threads instead. Likely you will not simply tighten to pull the part with no impact as they are tightened to 75 ft.lbs. or more. The axle spaces out the hammer to be away from rotor to lower possible damage to it as sometimes you have to give a pretty strong whack, miss a short puller end and you just scrapped the rotor.

  5. #5
    CB750 Member flatpick13's Avatar
    Join Date
    Oct 2020
    Location
    Texas
    Posts
    13
    Ok, thanks amc49, I appreciate the advice! I already ordered a shorter pulled with a 19mm hex end instead of the axle, but I think I can make it work, will just be careful of the rotor pops off

  6. #6
    CB750 Member flatpick13's Avatar
    Join Date
    Oct 2020
    Location
    Texas
    Posts
    13
    Sorry, was reading this one my phone, just got what you were saying about pulling the rear axle from the rear wheel to use as a puller... thanks, thatís saves me a few bucks too!

  7. #7
    CB750 Guru amc49's Avatar
    Join Date
    Sep 2015
    Location
    Fort Worth TX.
    Posts
    3,386
    Axle is long enough to hold it as a handle to keep rotor from striking the floor which will likely ruin it. Use like a 5 lb. baby sledge, I know it sounds like overkill but the best way to get it off in only 2-3 whacks. Small like construction claw hammer will beat it to death with no loosening. You MUST keep positive contact at all times axle to crank nose or your blows are wasted to damage only.

    Do it right and off in 2-3 whacks, do it wrong and nothing, you beat parts to smithereens. Possibly ruining crankshaft too. Why you bolt cases back up, to stop crank from impacting cases and bearings as much. Mainly the side journals that locate the crank.

Similar Threads

  1. how to remove alternator tensioner from top case of 700
    By Houredout401 in forum The DOHC Garage (1984+)
    Replies: 0
    Last Post: 06-04-2019, 08:21 AM
  2. Canít remove head
    By Longer in forum Engine / Exhaust
    Replies: 10
    Last Post: 02-18-2018, 06:20 PM
  3. How to remove baked on gaskets?
    By Chris in Dorset England in forum The CB750 Garage
    Replies: 8
    Last Post: 04-15-2017, 07:06 PM
  4. Countershaft seal - split the case?
    By vanbiker in forum Engine / Exhaust
    Replies: 6
    Last Post: 10-20-2016, 07:50 PM
  5. split rims dismantle
    By will750 in forum The DOHC Garage (1979-1983)
    Replies: 1
    Last Post: 03-07-2013, 04:30 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •