Topic: 80,s Honda Alternator Question.

[754]

I need some info on the inboard style alternators (or 3ph generator) used on the CBX and Nighthawk models, and maybe more. I want to use one of these on a project.

They seem to be gear driven, but I cant find the info on them, they are mounted behind the left cylinder and above the transmission.

What I need to know is if they are overdriven, & if so by how much?

I have asked before but did not get any info..

Thanks..

[TwoTired]

I don't know if I can give you the answer you are looking for.

I do have a CB700SC with the alternator arrangement you describe.  I don't have (haven't had) it dismantled.  I do have the Shop manual.
The alternator is chain driven off the crank with the far smaller sprocket on the alternator drive, indicating it is over driven.  I don't know the tooth count, though.

If the drawing in the shop manual is to scale, the diameter ratio between crank and driven sprocket is 29:10.  Also unknown is if there are any other couplings/gears between the driven sprocket and the alternator shaft itself.  However, the drawing at ....
http://www.cmsnl.com/honda-cb700sc-86-nighthawk-s-us_model7230/partslist/E++10.html
...doesn't appear to show any other coupling components.

If it is overdriven by the near 3 to 1 ratio, I'm pretty amazed.  The crank will spin over 10,000 RPM.  A 30,000 RPM alternator rotor is pretty impressive.  Specs say it will make 5A minimum at 2000 RPM.  Doesn't say what is makes maximum.

Cheers,

[Retro Rocket]

Yep the CBX has a chain overdriven alternator, those motors were one of the best inline 4's built, they had their idiosyncrasies but were a great engine. I have also been looking at an inboard mounted alternator and was wondering, is there any way of running the alternator off the shaft the kick starter engages to start the engine. I have never seen in behind the kick starter but i know something continually spins as you can hear  it if you hold the kick starter down after starting. I wonder if this would be possible?

Mick

[754]

I was thinking of running it on the crank but probably too slow, tho I need very little battery.

I could belt drive it on the left side but, carbs are a bit in the way, and I dont want to go to the front if avoidable.

The rotor is very light compared to stock and with a belt drive & idler, It could be unhooked in 30 seconds, for quicker revs.

The alternator I have here came off a Nighthawk, but I cant remember what was behind it, I took it off in 87 or so. I have the rotor, coils or windings, outer housing, and the finned regulator.

[bryanj]

Mead and Tomkinson in gloucester used to run a 24hour endurance racer called Nessie that was a Kawasaki900 with a citroen alternator belt driven from the LH end of the crank