TOPIC:

1977 KZ750 Twin
new AGM battery, new electrosport reg/rec

At idle the bike is 14.3. at 2k rpm and above its at 14.7  or 14.8.  Bike has been blowing coils. There are no bad grounds. Are those voltage readings normal, or an indication of overcharging? Ive checked everything but the stator, as I have no experience with that, and all looks good. Could this be a stator issue, or points, timing or anything else?

Thanks in advance

It's a tad high but nothing to worry about. It's the regulator that, err, regulates the voltage to the battery. Don't know what type of regulator you have on that bike but the old style Z1 open plate regulators were adjustable. Later enclosed ones are not.
I have a bike which chucks 15v into the battery across the terminals at 6k rpm and above and £14.8v below 6k rpm without issue. 

wrote:

It's a tad high but nothing to worry about. It's the regulator that, err, regulates the voltage to the battery. Don't know what type of regulator you have on that bike but the old style Z1 open plate regulators were adjustable. Later enclosed ones are not.I have a bike which chucks 15v into the battery across the terminals at 6k rpm and above and £14.8v below 6k rpm without issue.  

Thanks for your advice. I guess I will have to dig further to see why the ignition coil has cooked....twice.Of course, I dont have to tell you your bikes are amazing. I have a few myself, including a ZRX 1200R 

Coils generally cook because of excessive heat rather than excessive volts. Make sure the mounting bolts and heat transfer sleeves are clean, tight and have good clean contact with the mounts. The central bar through the coil is there to transfer heat from the coil core via the mounts then the frame. If the butting surfaces are cruddy that will reduce heat transfer. Additionally you could try insulating the coil somehow from engine heat and/or increasing airflow over it somehow.

Thanks for the compliments, gotta love a rex. 

Just got home from riding on my rex. Love how when ppl get aggressive, i roll the throttle and they are in my rear view. Still a fast bike. So here is the latest:

Today, with the bike stationary, i checked the battery with my multimeter while it was running. Stayed around a steady 14.5 between 1.5k and 4k RPMs.

Got home from riding my other bike and decided to check again (the garage is hot today btw), about 85 degrees.
Put the multimeter on and after about 3 min of stationary running, the voltage on the multimeter would dip from 14v to 10, then 13 then back up to 14.
The battery and reg/rec and ignition coil  are ALL BRAND NEW, put in just this week!
Note, both times the coil failed it was 90+ degrees outside with high humidity. Im thinking this is a heat issue, what do you think?

What are good ways to insulate the ignition coil

I suspect what is happening is excessive heat is causing the insulation between the primary and secondary winding to breakdown. Once that happens the coil is knackered.
So question is why is it overheating? Excessive engine heat or poor quality coil.
Coils, what coils are you using? 
Engine, excessive heat can be caused by timing, mixture, poor oil, and ethanol in fuel.
Air-cooled engines normally have an operating temp of about 250 deg.
If none of the above then the only thing you could try is insulating the coil with some heat reflective exhaust matting. 
Gotta say that I've never had to resort to that though.

Your readings should steadily increase with revs  until they hit whatever your reg hi output is set too and then should remain at that regardless of increased revs. 

thanks for responding!

1. the regulator is electro sport. a good brand. I had it for two weeks and it was on the bike when the last coil failed in 90 degree weather.
2. I think the timing could be bad on the bike, or the points which I havent changed for 6k miles lol.
3.Im going to check the stator, but the stator wouldnt cause the coil and regulator to fail would it?
4.The bike starts up on the first kick, it just sounds like its not running at full potential .. like murky, and its not the carbs.
5. each time the coil failed it was on 90 degree days
6. the revs increase until the voltage hits 14.7 and doesnt go any higher. however it stays at 14.3 at idle which I think is high, compared to my other bikes which are like 13.5 at 1dle.

OK, sounds like reg is OK, which leaves engine heat coupled with ambient temp. 
Ensure mixture and timing is good. Have you got or can borrow a thermal gun to see what temp the engine gets to? 

wrote:

OK, sounds like reg is OK, which leaves engine heat coupled with ambient temp. 
Ensure mixture and timing is good. Have you got or can borrow a thermal gun to see what temp the engine gets to? 
 

i dont know why i didnt think of this sooner! yes I have a thermal "laser" gun that I got way before covid made them popular lol. When the bike is running next, I will take recordings of the head temp, the coil, etc.

Could a hot engine make a reg/rec TEMPORARILY act up, and then go back to normal, or is it a case of when its fried, its fried? Like I said, earlier this morning I let the bike idle for a good ten min and got 14.5 volts with no drops. then later today, at idle, a few voltage drops, which is annoying. I really hope that "hot run" this morning didnt destroy the bran new rec/reg

Reg/rec is presumably mounted behind a side panel so we'll away from the engine heat. 

urankjj post= wrote: urankjj post=

glad that was deleted.

OMG you live in Kent? My nan lives there! Im british and american!!!