CB900 Big & Beefy Moto

notlob

Made in England
DTT BOTM WINNER
Time to make a start on the CB 900 I've had at the back of the shop. Was bought as a non runner parts bike about a year ago. I got it running by changing one of the pulsar coils then stuck it away whilst I finished the CB750 Brat bike.

My intention was always to fit different wheels, forks and swingarm so all the original bits were sold off a while back. It came with pod filers so no airbox but I have a set of 1st gen 1985 Suzuki GSXR750 Mikini Flatslide Carbs I'm gonna try and fit. They are 29mm VM29ss, similar to mikuni RS and not the mikuni VM smoothbores. Spacing is a mile out so it could be a challenge but I believe its been done before.

I got it out from beneath all the other junk I have lying around and thought it would be an easy job to get her going again

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After changing the oil and filter It was a bitch to start, would run on one pot or not at all, checked over everything, pulsar coils, I bought a new reg/rec as I used this one on the other build. Bought CBR600 coils as they are a good upgrade and plug leads.

I was messing around for a good few hours was getting a spark, plugs were wet but still no joy.
Then I gave my dumbass a kicking. I had been using a spare plug to test the spark, not removing the plugs only removing after a few trys to clean when they were fouled. Turns out 3 of the plugs were duff.

Few days later the plugs arrived and she fired right up. Result.

Now I had it running I could make a plan of sorts. I already bought a while ago a complete 2000 ZX9r front end. I wanted the RWU forks for the period look and they are a beefy 46mm stanchions.

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I bought a blackbird swingarm as well a while ago and Zx9r rear wheel

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Well that was the plan, but last week I saw a bike that changed my mind and I am now going to fit a 2007 CBR600RR prolink swingarm.

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The beauty of the prolink arm is I only have to make one shock mount on the frame the top mount is on the arm. I have to modify the sides of the arm as its wider than the CB and therefore the internal bearings and spacers. When I get all the wheel spacers and rear caliper and carrier I can work it all out.

To bring it up to date today I got my Zx6r yolks back with the CB steerer stem fitted, needed a bush for the lower and the upper easing out to fit the cb stem. For the eagle eyed amongst you I did say ZX6r yolks, I'm using these as the top yolk is flatter and slimmer than the ZX9r top yolk and I need all the length I can get.

Forks fitted
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I ground off the steering stops and steering lock bracket. Next is to make a new steering stop and weld it on.
 
Update from the past few days

Made a steering stop, took a few hours of sawing filing, fitting and filing to get this little piece

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here it is welded on

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After much measuring and pontificating with the ZX6r wheel in the CBR swingarm I decided that it was going to be to much machining to get the alignment correct. I really wanted matching wheels so relunctantly went for a CBR600rr wheel thats a drop in in the swingarm just waiting for a sprocket carrier so I can align the front and back sprockets. Will still need some machining of the carrier and more than likely an offset front sprocket.

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maybe if funds allow I'll get a cbr front wheel to match but for now heres the Zx wheel fitted

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6 pot calipers came with the front end. I gave them a clean up and blew the pistons part way out to inspect. They could do with replacing and although the body was protected with grease the dust seals look to be lifting which means corrosion underneath.
At some point I will probably replace them with some 90mm spacing nissin 4 pots, a lot cheaper to refurbish.

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Got around to fitting the cbr swing arm today, attacked it with a a big Bastard file, just needed to remove 4mm from the non drive side. Got it good enough to square but its not viatlly important its accurate as there will be 1mm clearance to the swingarm frame bosses and it tightens against the spacer and roller berrings ID's, not on the end caps like the original CB swingarm.

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Just fitted it with just two roller bearings in and the spacer to reduce from 20mm ID to the 16mm spindle.

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No clearance issues with the back of the motor

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I then got busy with the angle grinder and cut off the back sub frame.

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And the mainstand brackets came off as well, the lower shock linkage will attach here but will need some strengthening.

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Also going to need to repair this hole. The unfortunate consequence of 30 years of British weather.

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This how she looks now, the rest of the sub frame will come off in time just need it now for the rear tank location.

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Need now to get the swingarm spacers tuned down to size. Have some Nissin 4 pots calipers already refurbed on their way, cost less than it would for just new pistons on the six pots.
Also got some 12mm ally plate to make some rearset mounts and some steel plate and tube to strengthen the shock linkage mount and make the rear subframe.
 
Progress has been a little slow. Got some swingarm spacers machined up by a friend but forgot to take pics before fitting.

Heres the swingarm fitted

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The tank I have on there is off a F bike its spotless inside and out although its a rubbish paint job. I want to use a KZ tank like in the previous photos as they are about 2" shorter but the ones I have all have a few dents and are nowhere near as good as the F tank inside. I'm looking to turn the tank seam over to give a smoother look and fit a flat tank filler but I'm reluctant to start beating such a good a tank about.

With the swingarm fitted I have some idea of chain alignment. I have a 9mm offset 525 front sprocket on order (3 weeks) so it looks like about 2mm to come off the sprocket carrier but I'll wait for the front sprocket and check alignment again before machining the sprocket carrier.

Also order some 3/4" tube for the subframe and need to get some spigots made to mount it.

Got hold of zx10 throttle tube and right hand switch gear, not decided on what to use for the left hand yet.

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This kept me busy for a few hours today
I was contacted by someone who had seen my previous CRD inspired CB750 and wanted a seat pan making.

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off to be covered tomorrow.

Well that all for this update hope to get the rusted frame sorted and the shock mount brackets done next.
 
Sold the 6 pot calipers and for less than a full set pistons for the 6 pots got these 4 pot Nissins fully refurbished with HH pads.

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Also got a replacement pulsar cover as the original had taken a few knocks.

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Progress has been slow lately.

Got around to making a headlight bracket, there are two M6 bolt holes on the front of the lower triple clamp that I thought would be ideal. I made a template first then made the bracket out of 2mm aluminium plate. I left the lower lip long as I have yet to decide on the final position of the light.

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As you know there is always a better idea idea waiting to spring from the depths of your mind. So when offering the finished piece up I realised it may be better to fab a bracket from the top yoke and use it to mount the speedo as well. Ahh well that was only 4 hours wasted.


I need to get the carbs mounted as they effect the tank position I dont want them touching the bottom of the tank. I'm using 1st gen GSXR750 flatslide carbs, VM29ss not to be confused withe the smooth bore mikuni vm29 these are suzuki oem versions of the mikuni RS flatslides.
I'm using using 38mm marine fuel hose to mount the carbs as the spacings are different from the CB900s. Took me 6 hours of cutting grinding test fitting to get them right.

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If it wasn't for the petcock placement I would of been able to get them closer to the head but as it is the are 50mm away which is OK.

Decided to see what the rear end would like and to give some perspective of what I need to do to make the subframe.

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The intention is to shorten the seat and reshape it, still want a dual seat as I intend to take the other half out on it, so I need to devise a cowl to cover the passenger part of the seat when not in use. With seat shorter the gap for the top shock mount in the plastics will go and I can somehow integrate it into the side panel which will probably be cut down to flow into the tail piece.
 
I have a cb900 supersport I'm building and putting GSXR carbs as well. Curious to know if you put any copper piping in the marine tube. I know the guys on CB1100f forum put inserts when using radiator hose.
Like the build so far and can't wait to see the outcome.
 
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