Author Topic: CB 750 F2  (Read 914 times)

Offline Oddjob

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Re: CB 750 F2
« Reply #15 on: August 03, 2018, 11:44:37 PM »
Don't buy All Balls tapered bearings, they are made in China and are poor quality.
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Online Moxey

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Re: CB 750 F2
« Reply #16 on: August 03, 2018, 11:54:31 PM »
I ended up getting the steering stop, gussets and front down tubes welded by my in-law (stick welding big lumps of metal I'll have a crack at but thin tube I'll leave to the experts!).

No photos after the welds before I took the frame, swing arm (sans bushes) and stand off for powder coating but should be apparent where gussets were (headstock tube to spine, swing arm pivot point and rear frame).




SumpMagnet you asked about VIN plates and Painting in your thread, I opted not to risk damage to the original (my painters advised against leaving it on from past experience) so I drilled out the rivets and put the heat gun on for a few minutes to soften the glue, my original was a little scuffed anyway so I purchased a replacement plate from http://www.vin-plate.co.uk/ and had it engraved at work (a trophy makers or equivalent should be able to do the same) going to rivet it on this weekend.

Fitted new headstock races from All Balls




Achieved with home made bearing press (old bearing and threaded rod)



I also pressed in replacement NOS shock bushes in the swing arm.


I also fitted needle roller bearings in the swing arm (I considered bronze bushes but time constraints and finding a reliable supplier led me to the easier option of the roller bearings from WeMoto).

@Oddjob I purchased on recommendation from some of the members on SOHC.net, is that a recent development or has it always been the case? Unfortunately already fitted as you can gather otherwise I might have sourced alternatives but no bother the front end is easy enough to work on.
78 CB 750 F2
77 CG 125

Offline Oddjob

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Re: CB 750 F2
« Reply #17 on: August 04, 2018, 09:32:30 AM »
It wasn't well known that they had out sourced bearing production to China, it came to light when they started failing. I try to source a reputable name like Koyo or NTN for instance.
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Offline Nurse Julie

  • 1973 CB750 UK K2.1977 CB550/4 Mongrel Brat. 1978 CB400/4.
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Re: CB 750 F2
« Reply #18 on: August 04, 2018, 09:48:22 AM »
If your swing are roller bearings fail, which I hope they don't, I always have stock of the bronze bushes.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline SumpMagnet

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Re: CB 750 F2
« Reply #19 on: August 04, 2018, 09:54:25 AM »
Thanks for the VIN plate bit...plus from what I was advised in my other thread, I think I will go that route too. With lots of pics to prove it's legit.

Curious about needle rollers for the swingarm. Is there any advantage to phospher bronze bushings? Needle rollers is what I am used to on bikes, though I also know what happens when you neglect them. Bought a Gpz1100 'with a fresh MOT' and a swingarm that could be pushed into the footrest hangers either side. Bearing cage was a goner. Apparantly...it handled OK. Sheesh.
I am sure I spotted a grease nipple hole on my swingarm. No nipple...but a clear threaded hole where one would go.
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Bryanj

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Re: CB 750 F2
« Reply #20 on: August 04, 2018, 10:08:22 AM »
Needle rollers are fine when they are rolling(hence the name) but don't do too well when only moving through a small radius. having said that keep them well greased( 1,000 miles MAXIMUM preferably weekly) and you will be OK for quite a while

Offline Rob62

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Re: CB 750 F2
« Reply #21 on: August 04, 2018, 12:05:08 PM »
Nice work.... If anybody wants any 3D models knocking up for cad/cam machining etc just let me know...so long as you know the dimensions i can create the model.

Online Moxey

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Re: CB 750 F2
« Reply #22 on: August 04, 2018, 11:29:44 PM »
Thanks for the info, I'll see how long I can get out of what I have fitted but i'll likely be stripping the bike again next winter for more engine work so a few bearing replacements won't hurt.

@Nurse Julie damn if only i'd posted earlier, will likely be in touch in a few months (Y).

Some CMA alloy wheels for a 750 F2 came up on fleabay around February which I acquired as an early birthday present to myself (they were also in Malton which isn't too far a trek to collect).

They came with discs, hub and sprocket along with some well and truly out of date mismatched tires, here they are after stripping.


And following bearing removal, powdercoating.


Got a full set of Timken bearings for them just need to source some appropriate rubber (I'm torn between the recommended Avons or my personal preference Michelin).

Now for the engine which was stripped alongside all the work on the frame.

Upon removing the valve cover me and my dad (he's got a bit more experience with these engines having owned 3 in the past) made a few discoveries, namely the probable cause of the oil leak....the head bolts were hand tight :o

Following this we found a few of the valve springs were upside down (some would argue this doesn't matter) and two exhaust valves had burnt out, once the barrels were off it looked as though the bores had experienced some light scouring to boot....astounded that it managed to start and run on all 4 to be fair!

No photos of the strip down but one of the head packed for reconditioning (the barrels and pistons too in another box) and the pistons prior to removing the barrels.




I'm led to believe that the owner before last had inherited the bike from his father, going by notes in the Haynes it came with he was 3/4 the way through rebuilding before he snuffed it and the son took over, possibly explaining some of the neglect in the engine.

Anyway I had already wanted to play around with the engine this just forced my hand sooner so I took it to a bloke the next village over my dad had done a few plumbing jobs for, Jimmy Norman,I knew he's big on his Harley and air cooled Suzuki engines turns out from searching on here he's done work on other forum members SOHC machines I also think he's done a few bits for John Wyatt so definitely the man for the job, decent crack too top bloke!

Soda blasted barrels, pistons and head (3 layers of paint apparently, the engine had been red and yellow in the past!)


Re-bored cylinders (more of a skim really, scouring was very light but detectable, still on original rings)

The head got ported, new valve guides (I supplied Bronze APE but if I'd known Jim would have sourced me Kibblewhite) and new springs.


Given more time gas flowing was considered but time and £, I'm still considering going for a big bore kit over winter but I'll be consulting with Mr Norman and others first, hell I might just be happy with the 736 running right so who knows on that front.
78 CB 750 F2
77 CG 125

Offline Rob62

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Re: CB 750 F2
« Reply #23 on: August 05, 2018, 08:52:38 AM »
Some nice work there....

Offline Laverda120

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Re: CB 750 F2
« Reply #24 on: August 05, 2018, 08:59:01 AM »
Great thread. Nice work. Keep posting.

Offline K2-K6

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Re: CB 750 F2
« Reply #25 on: August 05, 2018, 02:00:38 PM »
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.

Online Moxey

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Re: CB 750 F2
« Reply #26 on: August 10, 2018, 11:56:58 PM »
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).





« Last Edit: August 10, 2018, 11:59:24 PM by Moxey »
78 CB 750 F2
77 CG 125

Offline Oddjob

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Re: CB 750 F2
« Reply #27 on: August 11, 2018, 09:39:32 AM »
VIN plate is upside down I think.
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Online Moxey

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Re: CB 750 F2
« Reply #28 on: August 11, 2018, 10:13:47 AM »
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.
78 CB 750 F2
77 CG 125

Offline haynes66

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Re: CB 750 F2
« Reply #29 on: August 11, 2018, 04:26:25 PM »
for goodness sake, slow down!!! youre showing me up...
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