'81 CB750C modest build

[Spinnbait]

I finally got around to working on my first cafe project. It's a cb750c that I got in a trade several months ago. It already had some modifications, but I envisioned it a bit differently. I used Herculiner as my base coat, then OD before the Herculiner cured for a good bind. I finished it off with a clear coat for UV protection. The herculiner was mostly out of laziness in that I wouldn't have to spend hours wet sanding for a nice smooth job. I planned to use an old set of Brooks locking grips, but now I'm leaning towards cork or leather bicycle bar tape. The brooks grips will require me to hone the ID of the locks too much - so they're staying on my Surly.

Now I have to tackle the electrical and carb issues so I can get it on the road. I think that I'm going to spend the time tuning the carbs to run with filtered velocity stacks. For now I'll do a basic tune with the pods.

I'll get some outside pics before long, but it's blocked in by one of my hundreds of projects for the time being. I'll use the opportunity to service the rear drum brake and clean up the wiring.

Before I got my hands on it:

Tail painted and tank prepped:

Paint mostly done:

 

[Spinnbait]

Finally made some time last weekend to clear the carbs. I think I see where the vacuum from the stock intake is needed. I'd really like to run stacks. Anyone have any suggestions?

 

[Spinnbait]

Figured I'd do a complete tear-down of the carbs while I have the time. They need some lovin' pretty bad.
I may try to open up the jets a bit (80/120) and see if that smooths everything out. The it's off to the remainder of the electrical - tail lights, turn signals, etc.

 

[Spinnbait]

Carbs are clean. I redrilled the primaries to .80mm and cleaned the secondaries that were already 1.2mm. Then I sourced a complete wire harness so I can defile it myself as opposed to the previous owner(s).

The tank is currently being de-rusted via electrolysis in my WELL VENTILATED back yard. It is a really interesting process.

 

[Spinnbait]

I need ideas for the muffler. I'd like something that exits just past the front sets. I'm 5'8" so aftermarket rear sets aren't really a necessity. I don't really want the exhaust to be a "form thing". I really just want it to exist, function, and be understated.

 

[my-79-750-k]

I'd leave the exhaust long like it is. Shorty exhaust looks nice, but gets hot quick, as in it fries your lower half in any traffic.

Is it just me, or the pic, but is that front end raked out? It looks more like a stretched out "chopper" style front end for some reason. Maybe it's just the way the pic was taken? Don't run stacks, or pod filters with the CV carbs. Best thing to do is just get a good quality filter. Unless you want to swap some other carbs on there (hint hint). Best way to wake these bikes up, other than internals, is gearing. Choose quick acceleration or good high speed cruising, you only get one haha.

 

[cxman]

you cant drill the jets on a kehin or mikuni

they need to be bored and chamfered to flow right and the drill sizes do not exactly correspond to jet size/flow

i would order new jets it will be a nightmare and 75/110 is usually the magic for your bike and what i use if i have to rejet a set for customers

make sure you look up the relay mod for your coils and do it so you have reliable strong spark

check your charging system and battery without good clean power you will be hooped

 

[warpt_99]

I like the handlebar tape idea, you'll also find a lot of different color ways with them. you need a little super glue and electrical tape to keep them "locked" on though

 

[Spinnbait]

Thanks for all of the advice!

I'd leave the exhaust long like it is. Shorty exhaust looks nice, but gets hot quick, as in it fries your lower half in any traffic.

Is it just me, or the pic, but is that front end raked out? It looks more like a stretched out "chopper" style front end for some reason. Maybe it's just the way the pic was taken? Don't run stacks, or pod filters with the CV carbs. Best thing to do is just get a good quality filter. Unless you want to swap some other carbs on there (hint hint). Best way to wake these bikes up, other than internals, is gearing. Choose quick acceleration or good high speed cruising, you only get one haha.

I'll just touch up the exhaust with some VHT paint for good measure. The front is raked a bit more than I like, but it looks rather dramatic in the picture. Maybe one day I'll throw a Hayabusa front end on it.

you cant drill the jets on a kehin or mikuni

they need to be bored and chamfered to flow right and the drill sizes do not exactly correspond to jet size/flow

i would order new jets it will be a nightmare and 75/110 is usually the magic for your bike and what i use if i have to rejet a set for customers

make sure you look up the relay mod for your coils and do it so you have reliable strong spark

check your charging system and battery without good clean power you will be hooped

As far as jetting goes - I matched the 120 with a 1.2mm bit to give me an indication of size, then I drilled the others to .80mm. This is just a cheap way to test. I know that the flow won't be perfect, but it will give me a decent start. I also blocked the air cutoff valves as per my research. New carbs will likely see their way onto this bike down the line. I'll be happy to have an easy bike to work on after my PITA Monster 900ss.

I like the handlebar tape idea, you'll also find a lot of different color ways with them. you need a little super glue and electrical tape to keep them "locked" on though

Thanks for the advice on the bar tape. I'm going to double wrap them without glue at first so I an make sure I like it. Brooks bar tape is EXPENSIVE and if I don't like it I can transfer it to one of our bicycles.

 

[warpt_99]

Brooks is definitely a hefty price tag for everything they make. Check out nashbar and you might be able to find a non Brooks leather wrap for a few buck less. Good luck regardless and I'd like to see the outcome.

 

[Spinnbait]

Carbs are finished for testing. Fortunately for me, my fiance decided to use my pods for wine bottle candle covers on the patio as they "seemed like old garage parts" while I was gone for a month... :-\ I got them back into decent enough shape and taped them. I'll replace them later. I'm determined to run pods as I've gone too far to hold back now. Should be firing sometime today.

I hate the bar clamp fuse holder so it's about to get some angle grinder lovin' and an updated sealed blade fuse block. I'll post pics of this later.

BTW, she lets me get away with rebuilding pretty much anything on the coffee table. I could probably get away with an entire engine, so a couple pod filter sacrifices isn't a big deal. She just knows that the garage is my zone now.

For now:

 

[dualero]

Why tape them? Is there any performance gain/mod by doing this?

Sent from my GT-I9300 using Tapatalk

 

[Spinnbait]

Why tape them? Is there any performance gain/mod by doing this?

Sent from my GT-I9300 using Tapatalk

It's a bit of a two part theory. First, they were slightly dilapidated and the tape will hold them together for the time being. Second, I'm hoping that it will increase the vacuum. We will see. I loose nothing if it doesn't work.

 

[Spinnbait]

Old and ugly:

Modified and kinda pretty:

 

[Spinnbait]

All back together on the bar front. I dig the "burly Russian girl" vibe that's going on with this build. Nobody's gonna steal her because she'll ride rough and insult your manhood with vodka breath.

I could use some bar clamp risers. Does anybody know of some for this bastard of a bar clamp?

 

[Spinnbait]

Now Helga runs...

https://www.youtube.com/watch?v=EnkmZdk7xl8&feature=youtu.be