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Introduction - Cam'run_1776

3326 Views 47 Replies 8 Participants Last post by  woodsman
Hello, all:
I am a Maryland resident currently working on building a cafe racer out of a 1982 CB750K and 1981 CB750C. This is my first build and I'm a new rider, so although I generally work through the process on my own, I'm hoping to use this site to avoid stylistic or mechanical oversights on account of inexperience. I bought the 1981 CB750C first, then bought the 1982 CB750K after realizing it was an easier starting point (confirming what I read on this site).

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Doesn't look like you allowed for rear wheel travel.
I am going to replace the CB750C shocks with the longer K model ones, but that could still be a problem because I'm also installing the battery under the cowl and larger diameter wheels. If you know what travel I should account for, please let me know.
This is not a roadworthy, let alone performance, motorcycle. Parked is it's highest and best use.
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This is an '80's Honda performance bike.
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You don't need bigger or longer you need proper.
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I don't know what you have been reading but if a bike to ride is your goal then you are headed the wrong direction.
The frame mod doesn't allow for wheel travel and the correction for that is not longer shocks. In Ontario, where I am, the tires you bought aren't road legal. Look at the shape, does it look like it is made for cornering? You swapped out substantially lighter wheels, with a much greater selection of tires, for just about the heaviest thing Honda built. Putting the battery higher doesn't lower the c of g. Removing the air box from the bike brings in a host of new issues. Worry about a new pipe when you start scrubbing those.
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You seem like you are genuinely interested in putting together a good bike as opposed to lawn art and that will get you help here. Stop looking at or reading about these dopey Pipeburn POS motorcycles they have nothing to do with putting together a great riding machine. Look up Steveo's Ducati Imola build, it is a good example of how a pro completely changes the cosmetics of the bike and never loses anything that makes the SS a top notch performance motorcycle.

The other thought to keep in mind is when you are riding with a group is often the time when someone will want to try out a bike that another rider owns. As an example if you and I are together, me on my snotty, beat up, little 620 Monster and you on a Pipeburn special, we aren't swapping. Not just because I don't want to ride yours but also because I can see you know nothing about motorcycles and my Monster isn't your clunker. I don't want to find out you can't ride it but think you can.

Your framework is the real issue at this point. Put the wire spoke rims back on with the normal tires. Cut out your hoop. Take one shock off, put a ratchet strap between the seat pan and the swing arm. You should be able to tighten it down until the shock bottoms out. That's the travel you need. There are a couple ways to correct it. Airtech may have a seat pan you could use to cover the structuring.

Shocks, fork internals, tires and braided brake line upgrades would be money well spent. Wear and maintenance issues should be attended to. And then just ride it until you know something about the bike.

Progressive and Hagon are good suspension vendors. You can ask for tire recommendations. If you are a new rider don't go with clip ons, better a superbike bar. You want to be upright and comfortable when you are learning to ride, it's a survival thing. You want to e able to see what is going on around you because you have no muscle memory until you get many miles under your belt.
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I checked out Steveo's Imola build and that is on point, for sure. Are there more pictures somewhere, as I only found the one. So I have two bikes: the build is 1981 and the other is 1982. Although I am swapping parts for the benefit of the 1981, I'm going to keep the 1982 operational and fully address any necessary maintenance and repairs. That being said, I may ride the 1982 until I feel comfortable enough to start transitioning onto the 1981 build. The ratchet strap idea for testing the swing arm is great. I built the cowl (seat pan is still in progress) and don't see myself ditching it because I like how it turned out and want to apply my personal touch, but I can adapt it as necessary based on the swing arm range test.
Also, I mentioned earlier that a buddy thought he heard a motor knock in the CB750K. I have uploaded two videos to YouTube: one of the bike starting and one of a road test. It would be great if I could get some input on if there is a knock or not (hopefully the video upload worked).
It won't pass the ratchet strap test, you don't even need to try it.
Don't know what the cowl is, unless you're talking sleds but, carry on with your personal touching.
No, that cross bar thing was already cut off when I bought the bike. But that is more for securing the rear fender than anything else, anyways.
No, that was structural. If it were just for attaching the fender it would have been flat narrow steel rather than the formed.
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You are wrong, it is structural.

The tire bottoming out is the issue, not the shocks.

Making the spring stiffer doesn't increase the travel.

Your modification doesn't work. The tire will hit it and it doesn't give the shock mounts the rigidity they should have. You can do whatever you want, me I would cut it out and make something that works properly.
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