Boyer ignition coil

[muskrat]

G'day Fellas.
I was riding the old girl down to Campbelltown (130Km each way) for her yearly inspection. About 40Km in she stopped. After 5 minutes and a bit of checking fuse/wire connectors she fired up only to stop again a few Km down the road. This happened 4 times and as I was close to a mates place I left her there and rode the Rhonda home to fetch the trailer (a mate was riding the Rhonda with me).
My first thought is the coil breaking down. Testing it gives 4.2 Ohm on the primary but nothing on the secondary, should be 12Kohm. I used 3 different multimeters all showing the same.
Today I'll pull the coil off the Cafe and test it (same ignition system).
Am I barking up the wrong tree?
Cheers

[Triton Thrasher]

Sounds like barking up the right tree.

[muskrat]

G'dat TT.
Just went out and checked the Cafe coil. Same 4ohm and nothing! Why can't I get a reading on the secondary? Meter set on auto and tried set on Kohm, nothing between plug cap and + or - side of the coil.
Cheers

[sean]

have you tried just swapping coils , regardless of meter numbers ?

[muskrat]

G'day Sean.
Just found out the secondary is measured between the two plug leads and check OK @ 12K.
Will do shortly but I don't want to get 30Km from home for her to do it again!
Could the coil check OK when cold but fail when hot and come good after 5 minutes for a short while till hot again?
Cheers
ps: I'm not the sharpest tool in the shed when it comes to electricks!

[sean]

G'day Sean.
Just found out the secondary is measured between the two plug leads and check OK @ 12K.
Will do shortly but I don't want to get 30Km from home for her to do it again!
Could the coil check OK when cold but fail when hot and come good after 5 minutes for a short while till hot again?
Cheers
ps: I'm not the sharpest tool in the shed when it comes to electricks!

nor am I but its been my experience coils do tend to break down when hot .....is your Battery reading up to snuff , no sign of a dead cell ?

[muskrat]

G'day Sean.
Battery tested good 12.8v 190cca cold, 13.8v running.
I do remember back in the day while bush bashing if a coil was breaking down just take it off, throw it in the creek, remount and ride for another hour.
Out to shed now to swap.
Cheers

[muskrat]

OK coil it was. Just did about 1 hour mostly at highway speeds with 4 knarly hills. All good, so now will buy a new coil for the Cafe.
Cheers

[Triton Thrasher]

I’ve had resin-filled coils get too hot because they were too close to the hot cylinder head.

[muskrat]

G'day TT.
The coil was a Boyer coil mounted on the top frame rail with the Boyer heat shield. The Cafe one was mounted in front of the head but an after market (read Chineseium) but no where the amount of miles.
Ho hum just another days pay.
Cheers

[muskrat]

G'day Fellas.
I do remember a few months ago I was riding her to work (60Km) and she stopped for no reason. Started back up after 10 minutes. I should have investigated then 
Cheers

[Bsareg]

As I understand it, with a double ended coil both plugs have to fire together (wasted spark system). If one lead or plug/cap is iffy the good side can't spark.

[groily]

Think that's right BSAreg. Both or neither is what it seems to be

The HT resistance only shows across the HT leads because neither end of the LT winding is internally connected to the HT one on a double-ender (while it generally is on a single output coil).
The same applies with, for example, the wasted spark Joe Hunt 180° twin magneto, which some folk here may use on some or other beast.
The pic here is a typical NipponDenso double-ender for a wasted spark system, 12v. Primary resistance is a bit under 3 ohms, HT is about 13K. Not dissimilar to what you've got Musky.
In this case, the resistor plug caps show 9K each.
Just sitting in a draw, no idea what it was off (Honda maybe?) but same design and construction I think as whatever is used with BB systems.

[muskrat]

G'day Fellas.
I got word back from BB. They say the coil can fail intermittently due to heat. The coil had been in it's place for many years and it wasn't a hot day, about 20C and done thousands of miles hotter than that.
I fitted the coil off the Cafe and gave it a test ride. Up and down Scenic Hill twice (2nd & 3rd gears) then up and down Tunnel Hill four times with about 10Km of 60mph between each. All good.
So now I'll buy another coil for the Cafe and a spare.
Cheers