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Author Topic: Honda CB750K Cafe Racer project about to start with a monoshock??  (Read 2094 times)

Offline rohalloran

  • Posts: 37
Can you verify that the linkage and mounting points were installed in the exact location that they were in on the donor bike? If not, then no way to tell how good it is until it's ridden. Leverage ratios are important on those setups.
It looks like they added the top mounting point directly from the donor right?

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It does look like that alright but I have no way of knowing for sure. All I know is the guy who did the work was extremely talented at this kind of work. He passed away a few years ago which was a real loss to the biking community as he could turn his hand to anything on a bike.

Offline rohalloran

  • Posts: 37
If the motor is stock, I agree that a set of bigger pistons and a mild cam would wake it up.  I just looked at teh intake manifolds and someone spent a lot of time on the conversion.

What have you been able to find out about its history?

Leave the frame color if it's not too chipped or pitted and get the wheels powder coated in Silver or white.  You could maybe get away with bright yellow wheels if the tank and seat picked up the yellow in some way.  Subtle?  Maybe not so much, but could look bold.

So the aluminium intakes were custom made you think? Not stock? I haven't been able to find out too much more really although I was told by a friend the carbs might have been off a ZXR 750. It's goign to be a fun project! The frame needs a to be redone but I won't go near any of that till I can get the engine running. Lots of ideas though!

Offline sebwiers

  • Posts: 33
Can you verify that the linkage and mounting points were installed in the exact location that they were in on the donor bike? If not, then no way to tell how good it is until it's ridden. Leverage ratios are important on those setups.

You can make a good guess if you work out the setup in software or even just start with a shock that is appropriate to the bike (from bike with similar weight) and work out a location that fully compresses the shock after an appropriate amount of travel.  The later is all I did for the back of my bike.  I ended up with a rate that is perhaps overly progressive, but the ride is fine.  As you say, the leverage is important, but its not to hard to work out, either with a lot of test measurements at different wheel positions or with a good diagram / software package.
« Last Edit: Jun 15, 2018, 11:18:14 by sebwiers »

Offline rohalloran

  • Posts: 37
You can make a good guess if you work out the setup in software or even just start with a shock that is appropriate to the bike (from bike with similar weight) and work out a location that fully compresses the shock after an appropriate amount of travel.  The later is all I did for the back of my bike.  I ended up with a rate that is perhaps overly progressive, but the ride is fine.  As you say, the leverage is important, but its not to hard to work out, either with a lot of test measurements at different wheel positions or with a good diagram / software package.

Thanks sebwiers. When the time comes I might be back to you on this one  8)

Offline clem

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Looking at pics of gpz900's online show the lever very close to 90 degrees with the shock. The one on this bike is way past that angle and you will have a very stiff ride as it sits.

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"After every war there are soldiers who refuse to surrender. To this day there are still thousands who cling to their 30+ year old motorcycles, thinking that the war is still on, refusing to concede that the four-strokes have won"

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Offline rohalloran

  • Posts: 37
Been looking at a good few pictures on line over the last 2 days and I now think the swingarm might actually be off a GPZ 750 because of the way the rear brake caliper is held on via the support bar. Plan to dump this and make a small bracket to attach to the swingarm like most modern bikes. Get a nice master caliper then to suit the back wheel that goes onto it. Thinking a GSXR 600 or SV 650 if there is the room.

Offline rohalloran

  • Posts: 37
Managed to get the head and barrels off today. Found out why it was seized and would not kick.. Outer 2 barrels had built up a layer of rust. On close inspection though I get the feeling the engine might have had been had a rebuild before it got left aside to ruin..












Offline BenHolmes21

  • Posts: 10
Looks a good base to get started on! Iíll be keeping my eyes out for this!


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Offline rohalloran

  • Posts: 37
So gave the barrels a light hone this eve to see what kind of condition the barrel walls were in. They are going to need a rebore for sure. The rust has left some wear on the walls so might as well do the job right.

Where to people suggest going for an oversized piston kit? The current pistons have a .75 stamped on top of them so I'm guessing that means they are oversized already? I see some people do an 836 upgrade but I'm not sure if i want to go that far with it.

Any suggestions are greatly appreciated. 

Offline rohalloran

  • Posts: 37
Managed to get the gearbox and crankshaft out of the engine casings this eve. One step closer to getting it ready to be soda blasted.