My 1978 Honda CB750 K8 cafe project

cxtex

cxtex

New Member
I picked up this bike earlier this year as a candidate for my next cafe racer project:


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I'm aiming for something like this (bike and photo credits go to Carpy -cb750cafe.com:


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Here's how my CB project looks so far:


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Current mods include:

Dyna ignition and coils
MSD wires
Raask rearsets
Fiberglass tank (sealed of course)
Fiberglass seat
Progressive rear shocks
Adjure tri-bar H4 headlight conversion
Woodcraft clip-ons
GL1000 front end with dual discs, trailing calipers, 37mm forks, Markland fork brace, Progressive springs, aluminum rimmed wheel (bolt on conversion)
Drilled front rotors
CBR600 master cylinder


Mods on deck (I have the parts, just need to put them on):

530 chain conversion (17-48 tooth sprockets and Diamond chain)
Steel braided brake lines
CC insert for Kerker 4 into 1 header (I had a Kerker can with the small baffle, but it was too quiet)
17 inch aluminum rim (gl1000) to be laced to CB rear hub (hopefully, this will not be too difficult)
Bearing conversion for swingarm


Future mods under consideration:
Battleax tires
New clocks (OEM gauges are not a direct bolt on to the GL1000 triple tree)
Ported head (I have a rebuilt head with HD springs and retainers, decked surface, and seated valves, but I don't want to stray too much from the stock engine. This will be my daily driver, and I don't want tempermental cold starts and diminished fuel economy)

I will try to add more pictures/notes as the project progresses. I welcome any comments, and if anyone sees me doing something blatently wrong, please point it out -this is only my second bike project and second bike I've ever owned; I am by no means an expert on this stuff, and any info I gather to finish this project only comes from my handy Clymer's manual, Google, the forums and my local motorcyle shop (Dougherty's -good peeps if you're in the area).
 
Way to go man, I think you're killin' it so far!
That bike has great lines and should be a blast to ride.
I'm looking forward to updates.
Are you going to shave the riser mounts off of the top triple tree?
You know you want to!
 
tobiism said:
Way to go man, I think you're killin' it so far!
That bike has great lines and should be a blast to ride.
I'm looking forward to updates.
Are you going to shave the riser mounts off of the top triple tree?
You know you want to!
Click to expand...

I'd like to shave 'em, but they're hollow, and the slit for fork clamping area runs a bit into the mounts. If I shaved 'em level, I'd have to somehow fill the void. I haven't looked into how to do that. I've ordered the early CB750 style idiot light cluster and will attach that to see how it looks. If it sticks up too high, I'll try shaving just the parts that hold the bar on both the cluster and the tree.
 
I think I started this thread in the wrong area. If any moderator wants to move it to the Big Projects area, feel free.

Anyway, got the CC insert, but wasn't happy with the sound. If ya'll aren't familiar with this thing, it goes into the end of your header pipe (collector). It would give the appearance of running an open header, but acts as a baffle. I got the three-disk model insert, and it was too quiet for me. I did happen to find someone selling a new Kerker Competition Baffle for the Megaphone can, and that one sounds real mean.

I was hoping to save the weight of an exhaust can, but looks like the Kerker will be staying on. I was told by the guy at Car Chemistry (CC insert maker) that if it was too quiet for my taste, I could cut one of the disks off (they make a two disk version for race applications). I may experiment with that.

The headers I have are not in the best condition, so I'm planning on sanding, sealing, and covering them in back header wrap.

No significant changes to the overall appearance of the bike, so no pics today. I'll probably post more pics after I get done cutting up the front fender.
 
Hey, I am going to guess you got that seat off epay?? If so I was bidding against you for it. I think what you did with it looks great though, went to the right place.
 
dan650plus said:
what kind of gas tank is that ? i have been looking for one like that. ???
Click to expand...

I'm not sure what brand tank that is. I just saw it on ebay one day and bought it. I knew I wanted to replace the stock tank with a Dunstall, or something similar. Looks like I ended up with something similar. It's fiberglass, and takes the old style two bolt petcock on the right side (stock K8 is on the left side and is the screw on type.) My local bike shop says it looks like it was made in the 70's when I brought it there to get it sealed (I heard untreated fiberglass and and today's gas don't mix well).
 
MBS said:
Hey, I am going to guess you got that seat off epay?? If so I was bidding against you for it. I think what you did with it looks great though, went to the right place.
Click to expand...

yes, I got seat off ebay a few months ago. It had the tore up upholstery with no padding. I didn't have any padding to put underneath, and I didn't like the way the pleather was put around the seat, so I drilled out he snaps and will try something different. The fibeglass is a little flimsy, so I may slap more fiberglass underneath to beef it up.
 
tobiism said:
Hey there, any updates on this project?
Click to expand...

I think I got the fender cut up the way I want. I'll add pics shortly. Other than that, the bike hasn't changed much due to the old lady naggin me, and basically just trying to perfect my aluminum polishing technique. My former "half ass" technique wasn't cutting it for the rear wheel. I obtained a GL1000 rear wheel with the 17" aluminum rim. I separated that from the GL hub and figured I'd lace that to the CB750 hub. Since I had the rim off, I might as well polish it, but I don't want to do it again later, so I wanted to get it right this time before I get my new Spitfire mounted.

I also thought I'd get some new spokes, and found a front and rear set on ebay. Well, the rear spoke set ended up being for an 18" rim. Now, I can't find any reasonably priced set for the 17" rim I have which the 17" tire I already paid for will be mounted to. Cheapest set of 17" rear spokes I could find was at a local bike shop for $90 (stainless), which isn't a bad price, but I already spent $100 on the other set. So I decided to try to restore the original spokes using a vibratory tumbler and that tin-zinc plating kit from Eastwood. They turned out pretty nice, but I don't know how durable (rust resistant) they'll be. Guess we'll see; I'm tired of messing with it, and I'm getting the tire mounted today.

I also got the oil cooler installed. I'll post pics of everything shortly.
 
Finally, an update. I threw the bike together with what I had just to ride it a few times before it got cold in November. Didn't have a camera handy to take pics though. There have been some issues that needed sorting out (clogged vented gas cap that I couldn't find anywhere, crack in fiberglass gas tank, spongy brakes, weak charging at idle). And to comsume even more of my time, this winter, I've taken a step backward as you can see in the pics below.

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I've dismantled the whole bike and trimmed unnecessary tabs off the frame in preparation for powdercoating. I've polished the usual engine bits and am currently trying to figure out what to do with the engine case regarding finish (paint, clear, blast and leave raw, etc...) I tried polishing the whole thing last night, but that's not gonna work. I really need to split the case to do it right.

My garage looks like a tornado has been through it, and I actually cleaned it up some. You can see in the background that my once cafe'd CX500 has been "un"-cafe'd to serve more of a commuter/light touring duty.
 
tjeeke said:
Wow, lookin good.
Please tell me more about the headlight conversion.
That looks sweet :eek:
Click to expand...

The headlight is an Adjure brand ($60-$80) H4 conversion with a Silverstar Ultra bulb (55/60 watt). I've got this setup on my other bike, and I can see much better at night than with the stock sealed beam set up.

But this sort of contributed to my charging problem. According to a CB750 expert on another forum, the high wattage halogen bulb combined with the Dyna ignition and 30 year old wiring will all suck up more amps than the alternator can supply -thus, the bike will be running on battery power at low RPM's. In order to keep the halogen set up, I had to lose the Dyna S and go back to points (but I kept the Dyna coils with the addition of a resistor kit). Before the conversion back to points, I was only making 14 volts across the battery terminals while at 2250-2500 RPM. Now I'm at 14 volts at 1500-1750....the resistor kit on the coils lowers the power requirement for the coils but still lets the coils give a better spark than stock coils. Besides, I cut wires off the stock coils to get the Dynas in, so there's no going back to stock coils.

I think if I disconnect the front running lights, use a different tail light bulb, and put some new bullet connectors on the alternator (ie. stator-field coil), I shouldn't have anymore issues with charging.
 
Looks like a great project, and will look killer when finished.

Could you tell me more about what's behind the carbs? What kind of air cleaner, any better pictures?

Additionally there's a guy over on SOHC4 that last week posted a cover for the handlebar clamp with hole for ignition for those running clip ons. Would really help your top end there.

Keep up the good work!
 
Awesome project! I'm in the process of doing the same swap with the GL1000 front end on my '76 CB750K. I see that you have the clipons...do you think clubmans will work with the GL trees?
 
UnCrash said:
Looks like a great project, and will look killer when finished.

Could you tell me more about what's behind the carbs? What kind of air cleaner, any better pictures?

Additionally there's a guy over on SOHC4 that last week posted a cover for the handlebar clamp with hole for ignition for those running clip ons. Would really help your top end there.

Keep up the good work!
Click to expand...

The air cleaners are Alphabet brand....apparently from Australia (that's what the label says). These happened to come with the bike when I bought it. Once, a while ago, I saw Carpy selling a set of these on ebay....I think they ended up selling for around $80. I haven't seen any other like these since. Here's some close-ups.

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Regarding the handlebar clamp...I already shaved most of mine off. I'll snap a pic of that too.
 
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