Having trouble splitting the Crankcases on my 1979 CB650.

[DANFROMOZ]

Hi All,
Just hoping I can get some friendly advice on the splitting of my Crankcases on my 1979 CB650. I'm a fair way through my build and have had the top end cleaned up, bored out, etc. I've decided to split the cases to check the bearings and chains, etc. I have all the bolts out, top and bottom cases, but was wondering what "really" needs to come off to separate the cases. My Manual takes you through the process of removing every single item from this engine, but I don't want to remove everything if I don't have to. I've already got the rotor off, then just screwed it back on lightly for now. Does the clutch and primary shaft really need to come off? When I see split cases it doesn't look like they do...? I have the timing plate off already too.
Any info would help right now and would be much appreciated. I've searched this forum for the answer but haven't found it yet... Thanks.

[DANFROMOZ]

Here’s a few pics of my project too.

[DANFROMOZ]

Ok, well I managed to get the clutch off, the primary shaft out and the Crankcase split today. Anyone wants pics, info, etc, feel free to let me know. I'll start looking at the bearings now and see if they need replacing.

[GeorgeSweety]

Hi Dan, I have only just seen this thread but I'm glad you sorted out your problem, I'm about to split the cases on one of my engines, well as soon as my wrist gets better, I seemed to have sprained it somehow.
Due to a PO's bodged attempts at doing Helicoils in the head bolt thread holes he has managed to totally screw up the top casing, if not the whole engine.
To make matters worse the Oaf then decided that as he could no longer get three of the middle head bolts to work he drilled the head bolt tunnels larger and tapped a thread in there so that he could bolt the head to the barrels where the three head bolts should go.
To make matters even worserer he didn't bother about all of the metal swarf that dropped down through his bodged Helicoils and his head bolt tunnel enlarging/threading and dropped straight down into the gearbox and turned into metallic soup that got pumped up the top end into the cam bearing faces on the head, cam and rocker box
On a lighter note, your project looks bloody amazing and if I were ever able to get off my arse and build a Cafe I'd be very pleased indeed if it looked anything like yours. Well done mate!

[Volker_P]

Just for completeness:
I once split the crankcase with the engine upside down without touching the top end at all. I confirm that the rotor has to come off.
I did the job to replace gearwheels and so I had to dismount the clutch and transmission cams. I do not remember if the clutch needs to come off necessarily just to split the case.

BTW: The CB650 starter clutch is a known and quite common origin of annoyance.
if you have everything open that far, disassemble and check the starter clutch (the part with the torx bolts on the primary shaft), too.
If you can get the parts in time, replace the springs, the rollers and the roller caps before you put everything together again. Also have a close look at the housing.

[DANFROMOZ]

GeorgeSweety - Thanks for your concern mate. yes, I was glad to get it apart. Sounds like your case is going to a trickier issue with what you've mentioned. I made a bit more progress before enjoying my summer and leaving the bike alone entirely. But it's that time or year again where I tend to want to get back in the shed so I'm getting to work on things again. I have a build thread on SOHC 4 Owners Club with more detail of the build if anyone's ever looking for that. Thanks for the kind words regarding my build, I am really happy with it so far, I was concerned about getting the frame just right and getting the motor pulled apart and checked, & so far both have worked out well.

[DANFROMOZ]

Volker_P - Thanks for the response and sorry for my late reply. I'm yet to put it all back together so I will take a look at the starter clutch as you've mentioned, thanks. I've checked bearings, etc with the assistance of a mechanic friend and his micrometer and plastigauge and am happy to report that the bearings are all in great shape. I've been sanding the fins of the block and head and prepping for satin black paint. I've painted most of the exterior covers now and will paint the engine transmission next then scrape back the fins for that contrast I'm looking for. On ther side I'm also putting the rear hub together after receiving the Cognito Moto Rear Disc Hub and replacing the bearings, etc. I painted the Rear Hub cover (engine enamel) and baked it. I'll try to get some pics up at some point.