Alternator swap - 1st gen bike, 2nd gen alternator?

[ldbandit76]

I've got a 1997 Bandit 1200S.  The alternator puts out about 400 W at 5000 RPM.  I'd like more.  I hear rumor that the second generation alternator puts out 550 W.  That would be nice...

But, they are not outwardly identical, per the fische at Ron Ayers.  
1st gen p/n: 31400-19C10
2nd gen p/n: 31400-03F40

They both have a 3-bolt attachment pattern, and both use the same output gear: 22730-27A05.  

Has anyone done this swap, or compared the alternator housings to see if it might be possible?  

Failing that, does anyone have a 2nd gen. alternator that they'd be willing to let me borrow (for a hefty deposit, but right of return) so I can compare?

Dave

[Red01]

There's no change to the motor, so I see no reason why you can't. You might need the wiring plug from a 2G, I'm not sure. Never really paid any attention to the connectors on a 1G.

[ldbandit76]

I'm becoming convinced that the newer model of alternator for the Bandit will physically fit on my first-gen bike.  However, the main fuse on my ride is 30 amps, wired between the alternator and battery.  That's 420 watts maximum, at the usual 14 V operating range of the system, or less at 12 volts nominal.  The new alternator puts out 550 watts.  

Does this mean that I would be unable to use the extra capacity of the new alternator, or at least that I'd have to wire directly to it, instead of to the battery?  Or is there another option?

Have any of you circumvented main fuse limitations?

Dave

[PeteSC]

The main fuse on the newer Bandits is 30 amps, also.  I don't see any reason you wouldn't be able to use the extra capacity of the alternator....it's just going to charge the battery a little faster, give you a little more oomph for aftermarket lights, etc.
  You're not intending to run a microwave oven while you ride, are you?
  Just a thought, maybe the reg/rect won't handle another 150 watts?
 I can't seem to find any specs.
  Maybe you can find a used, new style alternator on Ebay.

  If this is a 'plug and play' mod, it would be a real plus for touring riders, and riders running heated stuff.
,

[ldbandit76]

The main fuse is between the alternator and battery.  That means that all amperage at the battery terminals goes through it, so everything wired to the battery will be run through the main fuse.  A 30 A fuse limits total system draw to 360 W, regardless of alternator capacity (unless I wire up a separate circuit directly to the alternator).  That's slightly less than I'd like to draw with lights and heated gear.  

The regulator/rectifier is built into the alternator.  I would hope (and I presume here) that a high-capacity alternator would come equipped with a high-capacity R/R.  But I could be wrong there, too.  

No, no microwave.  On board refrigerator.  

Dave

[Kickstart]

Hi

Looking at the wiring diagrams it looks to me as though what goes through the fuse is the excess current from the charging system. Ie, that which is left over after powering lights, ignition, etc.

All the best

Keith

[ldbandit76]

Hi

Looking at the wiring diagrams it looks to me as though what goes through the fuse is the excess current from the charging system. Ie, that which is left over after powering lights, ignition, etc.
Keith

I don't think circuits work like that.  All the current has to come from somewhere and go back there; none gets "used up" en route.  If the fuse is between the alternator and all your loads (and it is) then everything from the alternator has to go through the fuse.  

From a more practical perspective, the fuse wouldn't work if that were the case.  Nothing draws more power than a dead short.  So if you have a short somewhere, and the fuse only handles "leftovers," then the fuse won't see the high current, and won't blow.  

Now voltage is a different matter, but voltage doesn't blow fuses, and, since everything on a bike is in parallel (except for the fuses), they all see 12 V (or 14.5) all the time.  

Dave

[Kickstart]

Hi

There seem to be 2 wires from the alternator / regulator / rectifier. One is red and goes via the main fuse the the battery and also via the ignition switch to the electrical system. The other is an orange wire which joins the wire from the ignition switch and goes to feed all the smaller fuses for individual circuits.

As such the only current going to through the main fuse will be the excess current from the charging system in one direction, or the complete load from the battery in the other direction depending load / charging, etc.

All the best

Keith

[ldbandit76]

I'm pretty sure that second wire is the ground/negative wire from the alternator (I don't have my wiring diagram handy).  That would make it the return path for all the current in the bike's electrical system (a circuit must go in a circle).  

I'll double-check my wiring diagram tonight, but the easiest way to check would be to put a voltmeter on the red wire and the orange.  If it reads anything but 0 (probably 12 V with the bike off, 14.5 with it on), then the orange wire is ground.  If it's another positive supply, then it'll have the same voltage as the red wire, and the voltmeter will read 0.   Or you could test the orange against ground, which would be 0 if it's ground, or 12/14.5 if it's a supply.  

I don't think anything but the starter motor actually uses the frame for both ground and negative (all components are grounded to the frame, but have separate negative wires).  That means there needs to be at least two wires from the alternator.  

Dave

[Kickstart]

House is warm, garage is cold so I am not playing with the multimeter in there tonight

There is a seperate earth shown on the wiring diagram for the alternator.

The orange and red wires are joined together directly by the on position on the ignition switch, so if one was the positive and the other the negative then it would be a direct short and the wiring would likely melt.

All the best

Keith

[ldbandit76]

Sounds intriguing then.  I'll have to take a multimeter and my diagram into the garage this weekend, then.  

One wonders what purpose the main fuse serves if there's a shortcut around it, though.  Maybe "main fuse" is a misnomer, and it's only there for the starter motor.  

Dave

[Kickstart]

Hi

The starter motor is not powered through the fuse. The feed from the battery splits, partly going through the fuse and partly through the starter relay to the starter motor.

All the best

Keith

[Kickstart]

I'll double-check my wiring diagram tonight, but the easiest way to check would be to put a voltmeter on the red wire and the orange.  If it reads anything but 0 (probably 12 V with the bike off, 14.5 with it on), then the orange wire is ground.

Tried the multimeter and the voltage between the red and orange wires is ~0.15 volts (so basically nothing), with 13~14V between the arange and the earth on the battery, and the same between the red and the earth on the battery.

All the best

Keith

[ldbandit76]

Tried the multimeter and the voltage between the red and orange wires is ~0.15 volts (so basically nothing), with 13~14V between the arange and the earth on the battery, and the same between the red and the earth on the battery.

Keith

That settles it, then.  Thanks for taking the effort to look into that.  

The only remaining question is how much load I can safely put through the "main fuse" circuit, then.  If the only things past the main fuse are the starter motor and battery and just about eveything else works off the orange wire, than there should be 30 amps worth of wiring capacity (if not alternator supply capactiy) on that side.  I may not need to rewire anything at all.

I've got a line on an alternator, and my lights should show up this morning.  I'll update as the project progresses.

Dave

[Kickstart]

Hi

Be interesting to see how it works. Should provide plenty of power for things such as heated grips.

All the best

Keith