Topic: 79' CB750 K8 - Rookie questions

[MrJey]

Hi there,
my never ending CB750K8 SOHC project slowly catches up momentum and I'm about to approach the electrical issues with the build.
The idea for this bike is a clean looking 750 where the gas and oil tank as well as the battery and other electrical things are hidden underneath a glass/carbon fiber skin. (see attachement)

The skin is ready and I have to start finding space for everything. Goal is to be left with more than a 1/4 gallon gas tank 

Long story short, I need some help with the electronics and hope you guys can help me with finding the right parts.

Problem 1 - Battery:
Ideally I can find something very small like the AG-401 and still be able to use the electric starter. If there is no way, I will take out the starter.
Would it be possible to run two AG-401 in parallel to get more cranking-AMPs out of it?
How do you guys feel about a Lithium battery without a BMS?
Ar there any better alternatives?
What other components do I need?
If I remember correctly, Lithium batteries are not in favor of fluctuations in voltage!?


Problem 2 - Ignition, alternator, etc
Are there any modern upgrades for it?
Which ones would you recommend?


Problem 3 - Microcontroller Motogadget/Denali/etc
If I understood it correctly the Motogadget M-Unit replaces relays and fuses!? Is it generally speaking a good solution? Not too worried about the price but how much space do I really safe with it?
How does it perform on an older bike?
I'm designing my own front and rear light with LED's.
Any better alternatives?
What other parts do I need?


Generally speaking, the main goal is to save space, weight, and make it cleaner. Cost is secondary.

Cheers,
Tom

[Alan F.]

With cost being a secondary consideration I'm sure you can make good progress.

Have a look at these:

Wet sump conversion:
http://forums.sohc4.net/index.php/topic,169468.msg1966688.html#msg1966688

CB750A stator and field coil conversion:
http://forums.sohc4.net/index.php/topic,161381.msg1853601.html#msg1853601

Small battery info:
http://forums.sohc4.net/index.php/topic,51809.msg552428.html#msg552428

We have an entire M-unit section:
http://forums.sohc4.net/index.php/board,185.0.html

[calj737]

You can easily place the mUnit within the backbone "triangle" of the stock frame. If you are planning to retain the electric starter, you still need the solenoid. That too can be crammed into the same space. As for it's benefit versus stock, well it's cleaner and easier, you can reduce the wire gauge... does make using momentary switches (if that's your thing) a breeze. Nothing wrong with solid condition stock components. But I am big fan of the mUnit and it works exceptionally well on older bikes.

As for Lithiums, LiFe type are better, and Rick's makes a Lithium-compatible Reg/Rec. Don't leave home without it if using a Li- battery.

Based upon the "sketch", I think the Sumpthing would be a very good choice.

[MrJey]

Thanks for your feedback! I was already sold on the Sumpthing but when I modeled it up in my CAD model, I realized it interferes with the exhaust. Current idea is to make a rather small external oil tank and build a smaller version of the Sumpthing so at the end, the exhaust will clear and I have enough oil in the engine.

Thanks for the other links. I decided to go with a M_Unit.

Going on back to the battery question, how big of a battery should I use if I only start with my kickstarter? Could I use two batteries parallel? Also, from my understanding the original alternator would supply too much current for a smaller battery. Might be a dumb question, but do I need a different alternator or would a regulator solve this issue?

Thanks,
Tom

[Alan F.]

That's one function of a regulator on a bike, to control charging.
Why not design an exhaust that will allow the sumpthing?