1982 CB750F brought back from the death

jungalist

Been Around the Block
Tought i'd be nice to write up my latest project. I'ts been a while since i've been on here, got a bit older and the toys got a little bit bigger...

Storytime starts with a message I got of someone who knew a guy who needed to clean out his garage (his better half told him to) and had a stripped CB750 laying around. If I wouldn't get it it would be brought to the junkyard. Can't turn down a free motorbike so I went over, loaded it all up and drove it to my granddad where I had a empty storage from my oldtimer I just sold.

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The engine at this point was only held in with the 330mm long front bolt which was mangled and is where the project ended for the previous owner.

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Life happened and I bought some land and me and my girl decided to build a house so the project stood there for about 3-4 years.
 

Sderbyshire

Into Sailing, classic Triumph cars and motorbikes.
This should be a good project!
i just rebuilt the top end on one of those for a friend, great motor!
 

Jimbonaut

Over 1,000 Posts
DTT SUPPORTER
Love these bikes - what's the plan? I'll definitely be following along regardless, love me some DOHC shenanigans
 

jungalist

Been Around the Block
As soon as the house was finished and we moved in and were settled I remembered i had this thing laying around and decided to give it a go. Got the mangled bolt out, stripped the bike further down. Took the carbs out and gave them a clean, cut out any accessories made on the wiring loom and started piecing the bike back together. I had no idea of what parts might be missing and if the bike even ran so easiest way to find out...

Quick clean on the carbs, float bowls and jets.
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Got the bike assembled to the point where it would start up, running on 3 of the 4 cilinders, carbs were overflowing
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Started to make a list of parts needed to get it roadworthy, these included getting the engine running reliable, redo the whole braking system and ofcourse tires, chain and some missing parts.
 

jungalist

Been Around the Block
Rebuild of the brakes included:
-Hell braided brakelines (as the old ones were rusted shut on the inside from laying around...)
-Nippon rebuild kit for masters front and rear as well as for all 3 calipers as they were seized
-New generic brakepads
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Carbs were taken off again and received some new Keyster float needles
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Old Marzocchi Strada's were torn down, painted, cleaned and received some fresh oil and top mounting rubbers.
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jungalist

Been Around the Block
Love these bikes - what's the plan? I'll definitely be following along regardless, love me some DOHC shenanigans
At the moment the bike is already up and running, just catching up on the past for now post by post...
This was all previous winter, have been riding her last summer already;)
 

jungalist

Been Around the Block
Since the bike had a misfire and the ignition leads were rockhard these got a little overhaul as well.

-New silicon spark plug leads
-New NGK spark plug caps
-New NGK spark plugs (ofcourse)

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This is how she was sitting, almost complete but running well. Just the last final touches to get her on the road.
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New tires were mounted, Bridgestone Battlax BT46
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With this the new DID standard chain was mounted, new battery put in and she was ready to hit the road!
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So I went to the DMV, turns out I was missing last owners registration so I couldn't get the bike on plates. Went to the previous owner who couldn't help me either as he never registered the bike. He found the paper of sale from the guy he bought the bike from, after some research got in contact with that owner who appeared to be the first owner of the bike. He wrote me a permission to ask for a recovery of his registration so i could go to the police office with that. Long story short it took me about a month to get the right paperwork, after this everything should be a breeze, no? Couldn't be more wrong... Covid had delayed registrations by at least 3 weeks. At least i had time to thinker where these remaining bolts should have been.

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jungalist

Been Around the Block
First drive was kinda short, noticed some weird noises, turned out sice i had a 4-1 marving exhaust (which came with the bike) the center stand had nothing on the left to stop it from going too high. So it was hitting the chain and i also forgot to put the bolts in to stop the mouning pin from coming out. Quick fix and got on with it.

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Dampening wool was added in the marving exhaust as it was rediculously loud (but after it is loud still).
Oem passenger pegs searched and found, anything better than the BMW ones which came with the bike.
After a good month of riding it almost on a daily basis I treated myself on a renthal ultra low bar and some Biltwell grips as well as an adjustable brake handle (as I'm used to a short brake handle from my 600 hornet)
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Enjoyed the rest of the summer, no breakdowns nothing. really impressed with it myself, 75k (km) on the clock stock engine and didn't miss a beat. First owner also told me he had the bike from '82 up to 2013. He rode it for about 3 years after which he parked it because the wife wasn't too fond of it. Impressive as he put all those kilometers on there by himself in that short time. Needless to say the bike has seen more of the world as i probably have... makes a person feel humble, huh?
 

Jimbonaut

Over 1,000 Posts
DTT SUPPORTER
Damn, that went from zero to hero in a hurry - great save mate, your F looks great. Is there much clutch rattle? It's pretty common on these bikes but there's a pretty straightforward fix involving switching out the old, hard dampers for new ones. Made a huge difference on my bike (I rebuilt an '82 CB750F over a couple of years)
 

Sderbyshire

Into Sailing, classic Triumph cars and motorbikes.
Excellent work, love the new bars too.
James, interested in the clutch dampers as my friend is complaining of a rattly clutch.
here is Mark’s bike, in my workshop with my 550
steve
 

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Jimbonaut

Over 1,000 Posts
DTT SUPPORTER
Excellent work, love the new bars too.
James, interested in the clutch dampers as my friend is complaining of a rattly clutch.
here is Mark’s bike, in my workshop with my 550
steve
It's the Clutch Damper Repair Kit on this page -

https://www.vintagecb750.com/products/2/brake-clutch/124/clutch-plates-springs

Comes with fairly straightforward installation instructions, takes a couple of hours at most. What you're doing is removing the OEM rubber dampers from the back of the basket (which is itself not designed to be opened, and therefore you can't find replacement OEM dampers on any Honda parts fiche) which after 40 odd years are hard and brittle (and that's what causes the rattle) and replacing them with new. The difference it makes is really quite something - my bike went from having a significant clutch rattle to having literally none at all.
 

jungalist

Been Around the Block
Damn, that went from zero to hero in a hurry - great save mate, your F looks great. Is there much clutch rattle? It's pretty common on these bikes but there's a pretty straightforward fix involving switching out the old, hard dampers for new ones. Made a huge difference on my bike (I rebuilt an '82 CB750F over a couple of years)
Haha, ofcourse I HAD that problem too, we'll get there in a minute ;)
 

jungalist

Been Around the Block
As winter set time for adressing some problems I encountered:
-Engine was running a bit rough at times, especially when fully on temperature it idled a bit rough
-Fueltap was leaking when opened fully (until now I just opened it 3/4 and worked fine)
-Clutch rattled as well as some slipping
-Misshifts from second to 3th when going through the gears fast
-Suspension felt a bit wobbly when hitting a bump in the corners
-Marzocchi's leaked around the shaft
-Front suspension had a small leak
-Brakelight as well as right rear indicator had a bad connection

So out with the tools and this time moved the bike to my parents garage so i could work a bit cleaner (and warmer) than in the open shed at my grandfathers.
Pulled the carbs and went for a thoroughly clean on them.
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Air cutoff valves were all good as well as polished the slides
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All reassembled with new allen hardware, everything working smooth and benchsynched.
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jungalist

Been Around the Block
Bougth myself an All Balls rebuild kit for the fuel tap as a new one from honda cost over €120 and aftermarket couldn't find one with a 20mm thread.
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Reinstalled and workign fine, just a bit tough to open and close still but wil smoothen out eventually i hope...
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The front chain tenioner was wrecked a bit, the tread on the tension bolt was stripped out of the head so installed a helicoil and this wil hopefully do the job. Just hard to feel if the bold ismaking contact with the tensioner but it stays in at least...
The stripped out tread and tapping for the coil to go in.
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Valves were adjusted, all were a bit tight but could set them by mostly changing out the old shims. Just had to buy 6 new shims to get them on point.
went with at least 0.13mm (0.005inch) on the exhaust side and 0.10mm (0.004inch) on the intake side.
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I made myself a grid: valve clearance, thickness shim, new shim thickness and worked out how i could change them out as efficient as possible.
As you can see some gaps were very tight (0.05mm or 0.002inch).
For anyone doing this themselves, you'll need the valve tool, feeler gauges, a micrometer to measure the old shims and a small screwdriver for prying as well a magnet to pick up the shim out of the shimbucket. You'll need 1 shim to be able to change out any shim as the engine may not be turned without a shim in place.
 

jungalist

Been Around the Block
For the clutch I ordere myself a set or EBC friction plates, EBC heavy duty clutchsprings, a rebuild set to replace the old clutchdampers to get rid of the rattling clutch and a shift detent from Vince and Hyde Racing to get rid of the misshifts.
The clutch dampers I got were from Wout van Veldhuizen, you can find him on cb1100F.net, decent bit of kit.
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Finished product:
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Shift detent in place
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Clutch plates marinated in oil before installation
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I had to redo all this because when installing the shift detent, the shifter drum was rotated compared to the drum. This resulted in a very hard to find neutral as well as the neutral switch not working as it should. For anyone doing this installation, make sure your neutral is positioned well and everything is working as it should before closing everything back up...
 

Jimbonaut

Over 1,000 Posts
DTT SUPPORTER
Nice. I also bought the detent star from V&H, definitely makes for a smoother gear change
 

jungalist

Been Around the Block
Since the front forks were leaking I took out the forklegs, stripped them down and put them back together with new seals and dustcaps. Also treated the legs on a new coat of paint. First thing to receive some paint on this bike.
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Since the new shocks were in (YSS Bravo twinshocks) I decided I wanted to do something to the wobbly swingarm...
Found a old hydraulic pipebender at work and took some leftover heating pipe laying around with me for the weekend. I'll let the pictures do the talking
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Since everything cleared time to weld her up, give it a coat of paint and voila

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jungalist

Been Around the Block
Swingarm looks awesome. How come it was wobbly in the first place though?
As far as I know lots of people switch them out for CB1100F swing arms but they are hard to come by. Something about the tubular design which flexes quite a bit...
Hope this will solve it kind of and otherwise it at least looks good.
Only thing is I have to ditch the centre stand, but it's easily enough put back on to do maintenance on the bike and still have my paddockstands laying around too.
 

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