Coil seems to be overheating

[ukjules]

I have had my bike for many years 5 plus and not an electrical issue whatsoever.
I now have an issue with the coils that seem to be overheating when they didn't before.

Issue:
I noticed the coils have never been stock ones, they are slightly too big and are only connected
by one bolt to the frame. (I am thinking this is the issue here not allowing heat to dissipate with only the one frame connection. )
This however has always been the case and they have only started to overheat in the past month.

History:
4 weeks ago:
bike went onto 2 cylinders and ignition fuse blew
sorted a load of connectors and put in correct fuses.
Noted the regulator was one that had a sense wire and i had taken it off ! put back onto the live rear brake wire

2 weeks ago:
bike went onto 2 cylinders - no fuses blew
Piranha Ignition box very hot and smoking ....
Stopped for a while and managed to get back 30 miles on two cylinders and no further issues.
lh coil showed 1 as resistance - clearly shot

So assumed the ignition system was at fault and got a new one.

week ago:
new elec Ignition system fitted and another coil (the same) fitted (3.4 ohms primary)
- boy does it go better though and better on fuel by 10-20 miles per tank !
Noticed the coil connection bolts to frame getting very hot - remember i only have the one connection as coil to big)
I swapped round the connector bolts to near the primary end (they has always been on the secondary end) to dissipate the heat and bike has run fine but
when i removed the tank i noticed the plastic had slightly melted near the secondary end of the coil ?
It still runs mind !

Do you think the issue is the coil dissipates heat via the frame connectors , there are two of them !
Any thoughts be useful - can get stats instantly to assist if anyone needs more info.

[Agemax]

buy the correct coils for the bike!

[ukjules]

Slightly more technical detail is what I'm after !
The coils as are in now have worked fine for 5 years ! So what could have changed ?
Ithe only change is the moving of the regulator sense wire to the rear brake
Wire as opposed to the indicator ? No fuses have blown since I have done this.

But to make you all happy I have bought some coils for this bike new !
I will test these for resistance before I stick em on and provide detail
As this is getting into a v/I = r complication.

Ill compare power outputs before I swap em over and update
As I know you all won't sleep until the info is provided.

[ukjules]

The new gs550 coils arrived, cheap ones off ebay but made for the bike.
They can be connected properly with the two posts to the frame.
Now work a treat and a 60 mile ride supports that.

New coils:
Primary resistance: 5.8ohms (I have never known coils so high ? usually about 3-4ohms)

Voltage to coil – 12.46v - same as between battery posts


Amps=2.14a
Watts = 26.66watts

These now work fine and don’t overheat !
I assume it is the power (watts) is low and can be dissipated as connected properly.


Old coil 1:
Primary resistance: 3.6ohms
Voltage to coil – 12.46v
Amps=3.46a
Watts = 43.11watts
Old coil 2: (This one overheated and melted around the non-existent connector post to frame. I assume the 49w of power was too much for it from the old suspect 2^nd hand coil.
Primary resistance: 3.1ohms
Voltage to coil – 12.46v
Amps=4.01a
Watts = 49.9watts