1977 CB750 K7 Restore/ Mod avec mon Pere.

drpoyser

New Member
Hi all,

I've been picking up all sorts of information from this forum for the last month or so whilst searching all the usual places of eBay, Gumtree etc.. to get a bike to work on with my Dad.

After months of looking I've bought myself a CB750 K7 from an old chap up in Bradford that had been sitting in his front room for the last 7 years and just took delivery off it this Friday.

The bike itself seems in reasonable nick. The PO had bought a few parts for it (which he kindly sent all the receipts for) which included a new Motad exhaust, which has barely been used since fitted!

It also fair to say that Dad has gotten pretty excited about this project, which is great news as we'll be able to spend some good quality time together and I can hopefully glean some engineering skills from him along the way.

I will post some pics as soon as I can figure out how to link to them from flikr!
 
Ha found some kind of way!

As you can see she's not in too bad a shape. There's quite a bit of oxidization on the rear wheel and the tyre is pretty much shot.
The rear suspension is also an aftermarket part that is probably a bit longer than the originals.

After a bit of coaxing we got her running but suspect that the carbs will need a good clean and the fuel has been sitting in the tank for around 7 years also. The points have the correct clearances (these were new parts replaced by the PO) and we gave the sparks a good clean. There is also a bit of clutch noise coming from the bike, but Dad said this is quite common on old bikes that have standing a while.

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On the front of the bike we noticed that the forks will need reconditioning, and the front brake caliper was seized.
We took off the caliper and along with the piston being stiff, the swingarm was locked up also.

Having a look through the Haynes manual was useful in showing how to remove/replace parts, but there was nothing showing how to recondition the swingarm frozen to the bolt. We were unsure what to do about this as we did not know whether this was a screw in item or just a knock through.

At this point, out of nowhere, Dad said he thought he had a similar brake set in the garage and bang, out came an identical caliper he'd bought years ago on the off change that he might want to upgrade one of his older bikes from a drum to a disk but never got round to it.
As it turned out the swingarm on this was also stuck solid, so we decide to use this as a test bed and after trying to see if bolt would screw out decided that it must be a knock through and proceeded to slowly tap it out.
After a few tries out it popped, we cleaned everything up with a wire brush, a little sanding and put it all back together with some bronze grease.
We then did the same with the one from the bike but found the bleed nipple to be all worn and wouldn't fit the spanner, so we filed that to the next size down so we could get the brakes back on and bleed them through.

As we only had Friday to work on the bike (my folks are off to France for a week now) I'll probably not have any more posts until the weekend after next when I can next visit.

The plan is that once we get the bike sounding a bit better, we'll then be happy to start stripping it down to work on the engine, forks and all the bodywork.
Generally I want to do a restore job on this bike, but I fancy a few mods along the way like a lower profile seat and smaller indicators.

Here's a few more pics of the front of the bike & couple of us gurning with joy on the new bike.

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Ha, had to include these sorry!

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Do the Ton!

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I've got a '77 as well that I rebuilt with the help of my dad. It was a great project to work on together. I think the caliper on these bikes are notorious for seizing up. I had mine apart 3 times and it still squeals a little bit. You have to take the piston fully out clean it and the inside of the caliper spotless and replace the seal. The clutch noise should diminish once you change the oil and put a few miles on the bike. Those tires are probably pretty dry rotted if the bikes been sitting for 7 years, careful doing any test riding on them. When I got my bike last spring it hadn't been ridden since '01 and the tires had been on there since '94. Anyways, good luck with the build!
 
Hey all, thanks for all the well wishes and advice - I seem to have got the front caliper freed up totally now, but am going to take it apart again and soda blast it to truly clean it soon.

So last weekend, I went back to my folks and we got the bike started and gave it a few runs up and down the back lane behind the house - it all seemed fine so we decided the time was right to start stripping it down.

As it started
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Tank and seat off was easy enough
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It took us ages to unpick and thread through all the cables from the back of the headlamp case!
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Airbox out.
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Making a nice collection.
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Some 'interesting' electrics to deal with.
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Carbs out - the hose rings were totally rusted so we just clipped them off with some cutting pliers - these should be easy to replace right?
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Now this is where things started to get interesting. We'd got everything off the bike until we just had a rolling chassis and the engine.
The long engine bolts were totally seized in situ. something of an odd design decision we thought to have these bolts open to the elements.
Does anyone know if this is standard?
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This was our improvised way of getting to hammer and knock at the engine long bolts.
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Finally the next day we managed to get the engine out - courtesy of the engine casing cracking away from the front long bolt.
We're going to have to wield this all back up, but that shouldn't be too much of an issue. As you can see the long bolt is still in place.
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And here's how she stands.
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Next time I'm over, we're going to catalogue everything up and send the frame parts off to be sandblasted and powder coated.
I'm now looking around for different companies who can do this.

If anyone has any recommendations (UK based) that would be greatly appreciated! :)

Till next time.
 
Ah rad looks like you're really making some progress! Depending on what kind of modifications you're planning, make sure to get all the fab work done before you send it off to get coloured in. You'll see most people on here do away with the majority of the frame's tabs, airbox, side covers etc. Are you keeping the back end stock as well? Again, there's the cafe racer or brat hoop to deal with if you're going down that route. You mentioned you wanted a lower profile seat so make sure you know how to achieve that before you get the frame painted! In regards to places to get powdercoating, there's Armourtex in Hackney who CAN do a pretty good job, as long as you're straight with them and push for a good job, I've had friend's who have got bicycle frames done there, all with varying degrees of quality...
 
Cheers for the heads up cinqmars2.

I've decided to keep the bike as stock as possible, with upgrades only to the electronics, lights and the lower profile seat.
For the seat I recon I can use the same seat pan but just use a lot less foam - maybe replace with more modern gel materials so it will still be comfy on longer journeys.

I'll give Armourtex a buzz for sure though. :)
 
Nice find and good luck with the build. I have been looking at these amonst others for our next project but everything biger than a 250cc seems way out of my budget.
 
After a long hiatus, I finally got round to stripping the front forks today.

The seals and dust covers are going to need replacing and the brass washers are missing from the bottom screw (Allen key type).

I've got all this on order now but my main problem is that the forks stantions have the chrome worn through right where they rub against the seals.

The cost of getting them rechromed seems expensive though! Does anyone have any ideas or suggestions on this?
 
Back on track again after life recently got in the way and decimated all my funds.

Frame has been blasted and powdercoated.

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The Fork Stantions have been sent to Philpots for rechroming and the Fork rebuild kit has arrived from CMSNL - these should be done by the end of the month.

New Tapered Bearings arrived so we've rebuilt the steering column and retapped the Yokes.

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And many thanks to Doctor Jones, who's supplied me with a much needed 17" rear rim and a set shocks.

The original was so rusted I decided to just saw out the hub.
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The New Rim.
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As it came out - To be blasted, polished and laced up.
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As she stands.
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Just for fun, we grabbed the tank and seat from the (as yet unfinished) Mike Hailwood replica.
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If only they were the right size ::)
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That's the lot for now.

By the end of the month/start of April (I only go back once a fortnight) I'm hoping to get a rolling chassis.
Then the fun can begin with the engine.

Cheers.
 
So, I took the top end to be looked at this afternoon and i'm going to have to rebore the barrels.
I'm originally looking for a 0.5mm (61.5mm) oversize set of pistons & rings etc..

However the bore price will be same even if I go full wack to 65mm and those Wiseco kits are tempting but extremely expensive.
I just found this on ebay but it sounds too good to be true.

Has anyone tried these?

http://www.ebay.co.uk/itm/69-77-HONDA-CB750K-K1-K2-K3-K4-K5-K6-836cc-BIGBORE-PISTON-KIT-W-HEAD-GASKET-/261401717357?pt=UK_Motorcycle_Parts_13&hash=item3cdcc1aa6d
 
Quick update as it's been a while....

First off, this tool although cheap has saved me so much time restoring valves, bolts and almost anything small and rusty.

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Valve Before.

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Valve After.

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Here was the underbelly of the engine.

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And the mounts had gone :(

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All in all a bloody mess.

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Pulled the cranks apart and the good news was that it looked ok inside.

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This needs to be sent off for a nice paint job.

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More insides.

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Heh, saw this when polishing up my calliper arm. Couldn't resist taking a hipster shot!

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Hours (days) of washing in paraffin, and the cases cleaned up.

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Heads back from the engineers - Now a hefty 836cc 8)

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New Pistons.

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Jesus, this took the best part of a day....

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One reassembled lower crank.

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Putting the valves back in.

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New Rubber and we have a rolling chassis.

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Bits to polish...

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Boom.

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Frame ready to reinstall the engine. It was a bitch getting that thing out so we thought this would help keep the paintwork fresh.

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Wiring her back up.

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So the first start began well, until this....

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So back out with the engine.

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Turns out we needed to replace the oil rings, spent an afternoon driving round old bike shops and a few industrial estates till we found someone who sold the right sizes we needed.

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Then it started :)

After that the front fender came back from the powdershop up the road. We were astounded at their work as this was basically rust covered in black hammerite paint.

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The carbs had to come back out as it was running a bit rich.
After running it a while now, it seems that I'll have to move the circlip down a notch as I went too lean.

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And heres the brand new second hand (chopped up) rear fender in place.

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So final work to do is get the tank painted, build a new seat and get the carbs sorted.
With a little luck, I should be riding it around London in the next few weeks. Can't wait!
 
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