1982 CB750F... The resto-not

pidjones

Active Member
Jimbonaut said:
Primary shaft's in the freezer, cozying up to some bison burgers and fish fingers - I'll leave it in there overnight and then hit the bearing with the blowtorch over breakfast. Pretty sure that's what kitchens are for, and if they're not then no doubt I'll find out the hard way. Again.
I officially have never seen this thread....
 

The Jimbonaut

Active Member
Didn't work - I'll bury it back in the freezer and try again tomorrow. Guess it's with good reason this bearing is jammed on there so tight.
 

pidjones

Active Member
If you give up and decide on a new bearing (the only reason I'd take it off), you could remove it like we do the headstock lower inner race. Cut the outer race and ball cage off with a rotary tool and cutting wheel. Then carefully cut most of the way through the inner race and smack the slot with a cold chisel or fat screwdriver.
 

The Jimbonaut

Active Member
There’s a good reason for removing the bearing as I’ve recently learnt. Behind it is a housing that contains small, segmented rubber dampers. These can/do wear down - replacing them with new rubber allows for smoother operation of the primary chain and eliminates any chain rattle. Assuming of course that your primary chain is in good condition.


Sent from my iPhone using DO THE TON
 

The Jimbonaut

Active Member
Damn it's been a while. In the end, won ugly. Had the thing sitting in the freezer for about two weeks - not entirely because I wanted to get it really, really cold but more so because I forgot all about it. Life/work/summer(ish) getting in the way and that. Had at it with a bench vise and big chisel and pried the damn thing off. Bearing still spins cleanly, and with it removed I could finally get at the once-rubber dampers in the primary gear housing -



Good thing too, one of them looked all chewed up -



- and all of them were completely plasticized and cracked -



OEM originals are rare as pope shit but there's a guy over on cb1100f.net who makes perfect replicas. That'll do me.

I need to switch out some of the lower case main bearings (2 really) as they're showing copper - I'll replace all 5. Not the upper main bearings though (good plan?) as they look fine. All the colours have worn off the bearings themselves so that's that out the window, and I'm a little unsure as to where to look for the inked markings on the crank. Would the inked markings be on the 5 silver coloured parts of the crank (the part that sits in the bearings), or on the lobes? I can't see diddly.



I do however have it on good authority that replacing the bearings with the loosest replacements (in this case, bearings with a yellow marking) will work just fine - better looser than tighter. Also, the difference between the different coloured bearings is really fractional apparently, so replacing all 5 lower main bearings with yellows should - I'm assured - be fine. Anyone done this?
 

The Jimbonaut

Active Member
Learned that the letters (on this engine, BBBBB) stamped into the case refers to the size of the crankshaft bore(s) through the cases. As the letters are all the same, this means that each of the 5 bore holes are the same size. The letters are either A, B or C - these letters are then cross-referenced against (long washed off) inked-stamped letters on the crank lobes to determine what size (colour) main bearing shells to use.

As I need to replace two lower main bearing shells - but the colour markings on both of them has been erased - I'm thinking that, as a couple of the other bearings still have brown markings, that I can replace the worn bearings with brown too. Again, I'm assuming this because of the BBBBB stamps in the case - indicating that the bores are all the same size. Bueno?
 

Nybz

Member
It is a bit confusing in the Honda manual, but yeah you have to cross reference those stamped marks on the case with the ink stamp on the crank. (Which by now is probably invisible by now)
I think it would be a safe bet just to get yellows...I could see the colour on the sides of my shells. So I just replaced those with the same.




Sent from my iPhone using DO THE TON
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
They have a corresponding measurement and service limit. You have to measure them and see what you need, then get the color based on your measurement. Each color has a .005 range.
 

The Jimbonaut

Active Member
As anyone who's ever painted an engine knows (and as I'm finding out the hard way), preparation is nine-tenths of the chore...





But after (sporadic) months, it's starting to look like something. No internals at this point, just a mock-up -





Side covers still need deciding on, but liking how it's looking. I used DupliColor low gloss black engine enamel and polished some details on the cases.

Now to take everything apart and make the thing work. How hard can that be...
 

trek97

Active Member
DTT BOTM WINNER
Thats some crazy masking.

I just loosely half ass em all together w minimal bolts, (1 or 2 per cover)

Spray, let dry, disassemble, wipe paint off off un-painted parts w cleaner. done
 

The Jimbonaut

Active Member
Cheers gents, work on this bike has been pretty geologically slow since the summer started but thankfully I'm in no hurry to get it done. Which is a good thing - hit the year-in mark and still looking at a pile of parts 8)
 

The Jimbonaut

Active Member
Got the rest of the side covers etc painted, and a few details more details polished up as well. And, as I have zero restraint, couldn't help buttoning it all up (minus internals) with some new shiny hardware -





Few more details to finish up but it's almost done. Now that I've replaced all the old hardware with new stainless bolts, I'm on the lookout for a set of new stainless upper and lower crankcase bolts as well. Anyone know where I can get some? They absolutely don't need to be OEM.

Have some new cam chains in the mail. Also arriving soon are a set of yellow crank bearings, oil seals and primary shaft dampeners. Then the fun begins.
 

doc_rot

Oh the usual... I bowl, I drive around...
DTT BOTM WINNER
Looks great. I mask my engines the same way,its worth the results.
 
Top Bottom