Generator power output of a '78 750K?

[Hisvett]

I have been looking for output numbers of the charging system on my '78 but not seeing it in any of the books. I have changed out the stock seal beam headlight for an LED but also added a few other lights; aux Halo/Low Beam/High Beam lights, front side LED amber lights, rear tail/stop LED light bar and storage box with tail/stop LED lights and I also added a USB power outlet for my phone. I would think there is enough surplus power to take care of what I have added but looking down the road, I may want to add some plug-in body heating vest, leggens, gloves etc. The last thing I want to do is overload the charging system and wind up sending it up in smoke. Anyone ever been down this road?

 

[dirtdigger]

Well the spec output of the 750 is only 13 amps max, at idle the 750 doesnt output enough to even keep the battery charged with the headlight on. I think you will easily use more than than the 750 can supply with all the stuff you are wanting to run. Cycle x does have upgraded 20 amp charging system available which may be enough for your needs

 

[Hisvett]

Thanks dirtdigger for the lead on Cycle X, this is a new vendor for my bookmarks. I feel like I have just found a new candy store...I'm going to have to hide my Cc while surfing this site!

 

[dirtdigger]

Kenny is a great guy and I buy almost all of my engine stuff from them.

 

[Hisvett]

Well I got to thinking about this a little more, decided to take the bull by the horns and check this out a little more in depth. I just went out and fired up the ole steed, put my digital voltmeter on the battery to see just how many V's I had at idle, 2K and 5K revs. The results were mostly positive ....and Yes, all lights were on!

After warm-up, I had 12.15 to 12.21 V's at "Idle".....awesome, not draining the battery at the stop light.

At 2K Revs, the nubers went up to 13.5 to 14.1 V's....seems a little high but within limits.

At 5Km Revs and up, numbers leveled off at 15.5 to 15.8 V's....Now that really seems high to me as a guy coming from the car world, not so sure about the MC world.

Bottom line, I'm seeing plenty of charging going on, not so worried about current conditions but if I do add more items down the road, I will have to take another look. While writing this, I'm also thinking I need to take my 30 year old digital meter and test it on one of my cars against my OBDII scanner readout....just to confirm we are taking apples to apples.

Thanks for checking in.
MK

 

[brettp]

14v should be the max

 

[Hisvett]

14v should be the max

I'm thinking that too; once I confirm the calibration of my 30 year old trusty Radio Shack Multimeter, I will look that the voltage regulater. I'm assuming that it is not adjustable? No way I'm getting off the easy!

 

[brettp]

I'm thinking that too; once I confirm the calibration of my 30 year old trusty Radio Shack Multimeter, I will look that the voltage regulater. I'm assuming that it is not adjustable? No way I'm getting off the easy!

Nope, not adjustable.

 

[dirtdigger]

Well I got to thinking about this a little more, decided to take the bull by the horns and check this out a little more in depth. I just went out and fired up the ole steed, put my digital voltmeter on the battery to see just how many V's I had at idle, 2K and 5K revs. The results were mostly positive ....and Yes, all lights were on!

After warm-up, I had 12.15 to 12.21 V's at "Idle".....awesome, not draining the battery at the stop light.

At 2K Revs, the nubers went up to 13.5 to 14.1 V's....seems a little high but within limits.

At 5Km Revs and up, numbers leveled off at 15.5 to 15.8 V's....Now that really seems high to me as a guy coming from the car world, not so sure about the MC world.

Bottom line, I'm seeing plenty of charging going on, not so worried about current conditions but if I do add more items down the road, I will have to take another look. While writing this, I'm also thinking I need to take my 30 year old digital meter and test it on one of my cars against my OBDII scanner readout....just to confirm we are taking apples to apples.

Thanks for checking in.
MK

Actually your idle voltage is at a discharge, battery voltage at rest should be 12.6 volts in a good battery so at 12.21 your battery is in a state of discharge.....and this is somewhat typical of the 750. high end charging is 14.5 to 15volts so yours is a bit high but this can change a bit depending on type of battery you are using. And yes the voltage regulator is adjustable in the sohc although I have never had to adjust one. Also aftermarket electronic regulator conversion is a good choice. Also keep in mind high charging voltage doesnt necessarily mean you have a lot of charging, You can have high voltage and very little amperage available. The amperage is what you have to worry about especially with all the heated accessories you want to run.

 

[brettp]

Actually your idle voltage is at a discharge, battery voltage at rest should be 12.6 volts in a good battery so at 12.21 your battery is in a state of discharge.....and this is somewhat typical of the 750. high end charging is 14.5 to 15volts so yours is a bit high but this can change a bit depending on type of battery you are using. And yes the voltage regulator is adjustable in the sohc although I have never had to adjust one. Also aftermarket electronic regulator conversion is a good choice. Also keep in mind high charging voltage doesnt necessarily mean you have a lot of charging, You can have high voltage and very little amperage available. The amperage is what you have to worry about especially with all the heated accessories you want to run.

Thanks for adjustable note, I got that wrong it looks like. Sorry, Hisvett.

 

[Hisvett]

I was just going through my Honda motor manual and found a charging chart by RPM and how to adjust the voltage regulator. I also ran across an U-Tube video of a guy talking about the voltage regulator; he had nothing good to say about attempting to make an adjustment. He said it would open a real can of worms.....not that would keep me from trying it myself

Also, my battery is almost on lifesupport; if I don't keep the tender plugged in, it will go dead in a few days. This could also make the V's higher than normal....I believe.

I was thinking about the amps too; I can pull the pos terminal off the battery and connect my amp gage inline to check.

Thanks for the input(s)

 

[Hisvett]

1/11/24 Happy days! Voltage issue fixed....at least for now. I pulled the cover off the regulator (without removing it from it's mounting spot) and loosened the 7mm lock nut. Fired up the motor to watch the charging V's and DAMM! 13.8 to 14V's.... So I'm guessing 1. by wrinching on the lock nut broke the points free (from sticking or durity) or 2. In moving the wires around to remove the cover, I fixed a bad connection....I'm going with this one right now.

Before closing up the side cover, I pulled the plug from the stator, used a tooth brush to clean the blades, added a little dielectric grease before reconnecting. I made one last check after replaceing everything and still running right at 14 V's. I'm calling this case closed, thanks for the inputs. Now we move on to reworking the front brake or prehaps adding a second rotor.

 

[Hisvett]

April/24
Did another check and the V's were back up flurting with 15V again. So, I removed both the regulater and rectifier from my '77 parts bike and swapped them out.....once again I'm back down to 14v's at 5K. I'll check it again after a few tanks of fuel to see if everything is still hanging in there.

Next project; adding a second disc brake to the front for a little better stopping power! Photos and info to follow.