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CB 750 F2

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Laverda Dave:
Great thread. Nice work. Keep posting.

K2-K6:
Nice work and good progress.

I'd like to offer a different view of needle roller bearings in the swingarm pivot as I think they are ultimately the best solution for the job they've have to do.

There's also nothing wrong with bronze type bushes as they'll by far out perform the originals but need just as much lubricating as anything else there.
It's an area that I feel most of the original Japanese frames are very severely compromised with their original material's and makes one of the biggest improvements to handling available as an invisible modification.

Back to needle rollers, there are examples of low angular use that don't have any problems because of that.  Two stroke small end bearings are nearly all this type and only move through a few degrees,  they have no rotary cycle to change position.  What is normal as I understand it, is to have size and distribution of rollers in the cage to allow each roller to travel a distance to span the gap between them so that all the track is used effectively.
Another example is universal joints on vehicle's propshaft.  Normaly crowded roller and static grease lubricated intermittently, they offer huge load carrying capacity with small rotational movement and last for years and literally hundreds of thousands of miles.

As above, bronze bushes are a very good solution and work really well but in pure technical engineering terms, needle rollers offer qualities above that.  It's in the area of swing arm twisting as most of these old design are not that rigid.  If you get the arms to move then you are effectively putting the pivot tube into torsion which creates an S form of that tube and tries to move the bushes out of straight alignment. In this scenario,  bushes can effectively pinch and lock the pivoting action of the arm and makes any twisting load worse.  Needle rollers won't do this (they don't like it but won't lock) and offer higher performance under extreme load than plain bushes.

They should be fine with just yearly greasing.

Moxey:
Thanks for all the information guys and gals, it's given me a lot to ponder provided the motor functions I'm just going to run it and see what works and doesn't bearing wise.

Onto reassembly of the motor

Installed some imdpistons pattern rings (I wanted Honda OEM but Christ NOS prices can be lunacy, cost of this set for one piston!)


Rough diagram of ring assembly order visible above (I double checked with the seller also)

Here installed.


All pistons, with fresh rings and gudgeon pin clips reassembled, new base gasket and barrels fitted


Now its around this time (May) I cleverly severed my flexor tendons (with a tape measure of all things) so the limited photographic recording of the refresh fell short and luckily for me my dad took over fully with reassembly. Unfortunately this meant I missed the final stages of the engine rebuild along with early reassembly of the frame.

I did have input over the use of gaskets however and I did contact my dad to not fit the cheapo head gasket that came with the bike, I wanted to use an OEM head gasket but there seemed to be none available even after extensive ebay trawling so I resorted to the Cycle X top end gasket set (recommended by a few US contacts as been a quality leak free item...here's hoping!).

After being stung with a nice £30 customs charge (first time I've ever paid considering the amount I've bought abroad over the years) I had a nice top end gasket set (head, cam pucks, o-rings and valve cover) for my 750. The head was then reinstalled (I requested a bit of  blue Hylomar to boot just to ensure the head seals, just a little that is, I normally wouldn't but I've read so many tales of leaks and weeps I wanted to do everything possible to avoid them) and a little 10w40 oil dropped down the bores.

Fast forward to last week, the engine was fully rebuilt and the top end painted whilst the frame was like this


Then this


I'm at week 12 of my hand rehabilitation which effectively means I can use it normally again so I could do a little graft on the bike too.

Baby steps, riveted and glued replacement VIN plate (light taps with copper mallet and a broom shank to achieve the desired 'roll').


Then the big jump to engine back in the frame.




Original Comstars fitted for now until I can get the bearings and discs fitted to the CMA's (also affording new shoes for said wheels ;D).

Should hopefully be running again this week (Y) refitting the engine was a bugger, unfortunately with me been out of the picture for a bit my dad built the rolling chassis which is fine but I realised it would have been better to keep the frame bare and lift it around the engine but hey ho lesson for next time. I also opted to use stainless engine mount bolts from Zedparts but have found the lower carrier bolt they supply is 50mm too short for an F2 (don't think it accounts for the aluminium footrest holders) waiting on the replacement longer bolt from them soon, I would have just machined my own but time and machine access is limited (note don't fall out with your foreman even when he is wrong :P).

Moxey:
You know I was thinking that, I looked through at my old photos and it looks as though that's how it was mounted before  (did check beforehand) worried now it's been tampered with before.

haynes66:
for goodness sake, slow down!!! youre showing me up...

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