Topic: pamco and "ultimate high output coils" coil mounting help (NEVERMIND GOT IT)

[cheftuskey121]

title pretty much says it all. I am starting to run electrical on my bike, and want to get the coils in and sorted. there is no way in the world these "ultimate" coils from cb750supply.com with the ultimate pamco deal mount up to the existing coil brackets. the mounts in the new coils are horizontal whereas the stock coils are vertical. I searched but never found the answer I am looking for, just statements that people ARE using this combo

I am just plain stumped.

[Proto]

This probably won't be of much help, but I put the Pamco ignition and utimate coils on my 76 cB750F a little over a year ago.  I do remember that coils did not bolt in exactly as the old ones did, but with the a combination of the old and new parts, I easily got it mounted using the original mounting holes.  I think my problem was that the new coils were wider.  Of course my bike may be totally different than yours. 

[bjbuchanan]

I had to mount mine side by side but vertically on my 750. I have universal replacements that are slightly wider and butt up against the tank stopping it from going all the way seated. I bolted mine together using bolts I had and just hung em up

[cheftuskey121]

here are the stock coils



here are the new coils. I can put them sideways but I cant use one of the brackets (closest to camera) because the holes dont line up and the bracket bumps into the wiring tabs



I am curious if I cant buy or fashion very small and short right angle l brackets with extra bolts, washers, and nuts? I dont know if the wires are supposed to be run out sideways like that, I feel like they should be facing down. I am bad at fabricating, this is a new world to me.

side note. how do I know which coil wire if going to which plug? I know 1 and 4 are on the same just like 2 and 3. but do I designate which is which?

[cheftuskey121]

pretty sure I am overthinking. found this lovely picture right on the site for the pamco instructions. silly me.




still curious about which wire is for which plug etc.

[bjbuchanan]

Blue is 1-4

oldmanhonda.com or google search in the left toolbar. faster and easier

[Scott S]

 It doesn't matter. It's a wasted spark system. As long as you have one coil for 1/4 and one for 2/3,you're good to go.

[cheftuskey121]

I was just about to ask...but thanks Scott. thats what I was unsure about. I already know about oldmanhonda. what a coil thing to have for these bikes! thanks guys. I am already getting it sorted. I just needed to get away from the problem to solve it!

[70CB750]

Mine came with long bolts and spacers to intall them - just like the picture shows.  But I had senior moments like that before too 

[cheftuskey121]

Oh yeah mine did. I was just stuck on using the stock brackets. Couldn't see the trees through the forest. Long work days will do that to you. I feel like a dum dum. Carry on

[BuffaloBill]

I, just last weekend mounted them on my 76 750F.  The tank wouldn't go back on with them mounted like that pic shows.  I made a couple pieces from 3/16" steel to drop them about 3/4" and cut the spacers a little shorter.  Fits good now. 

[pamcopete]

I, just last weekend mounted them on my 76 750F.  The tank wouldn't go back on with them mounted like that pic shows.  I made a couple pieces from 3/16" steel to drop them about 3/4" and cut the spacers a little shorter.  Fits good now.

Bill, that's strange. I have not had a complaint about tank clearance using that mounting method. I use it myself on my '74 and there is plenty of clearance. Do you have a stock tank? Did you mount the coils with the terminals towards the front?

[BuffaloBill]

Hello Pete,

I have the terminals towards the rear on the right coil, and towards the front on the left.  I tried to see up in there, using a small flashlight, but couldn't really see enough to know for sure where the interference was.  I could see some paint deposited (from the tank) on the edge of the right hand coil (as you sit on the bike).  This is on a 76 CB750F.  With the spacer tabs I made the coil is that much closer to the valve cover-cover, but the plug wire still had a decent bend radius.  I slipped a piece of rubber vacuum tubing over the wire at those spots.

Like others' have reported, after wiring it, etc.,  the bike fired right up.  I do circuit design (mostly temperature controllers) for a living, and play as a machinist at home.  You did a nice job on your circuit board and machined parts.

Bill

I forgot to add that yes, I have the stock tank.  I enjoy this sort of stuff and would never complain about something I could easily take care of.

[lash]

I, just last weekend mounted them on my 76 750F.  The tank wouldn't go back on with them mounted like that pic shows.  I made a couple pieces from 3/16" steel to drop them about 3/4" and cut the spacers a little shorter.  Fits good now.

Bill, that's strange. I have not had a complaint about tank clearance using that mounting method. I use it myself on my '74 and there is plenty of clearance. Do you have a stock tank? Did you mount the coils with the terminals towards the front?

I have a 72 750K2 all stock and mine wouldn't fit either. Haven't fashioned a fix yet, but no way will the tank fit without doing something.

[Duke McDukiedook]

What is the resistance on the primary of those coils?
If it is not 5 ohms you killswitch will eventually get fried if you do not use resistors to up the resistance on the coil primaries.

[Bailgang]

I'd like to know the ohms on those coils too, being my luck the specs for the coils were right in front of my face but I couldn't find it.

[pamcopete]

What is the resistance on the primary of those coils?
If it is not 5 ohms you killswitch will eventually get fried if you do not use resistors to up the resistance on the coil primaries.

The stock points coil has a primary resistance of 4.5 Ohms so when the coil is on, the current would be 14/4.5 = 3.1 Amps, but the coil is only on for slightly more than half the time with a 190 degree dwell angle, so the average current is 190/360 = .53 X 3.1 = 1.64 Amps. The average current is what would affect the contacts of the kill switch, not the peak current.

The 17-6903 "Ultimate" coil has a resistance of 2.5 Ohms, so its peak current is 12.8/2.5 = 5.12 Amps but the PAMCO rotor has a 120 degree dwell angle so the coil is only on for 120/360 = .33 of the time so the average current is .33 X 5.12 = 1.69 Amps

However, in both cases, there are two coils powered by the same kill switch, so the average current that the kill switch sees is 1.64 X 2 = 3.28 Amps for points and 1.69 X 2 = 3.38 Amps for the PAMCO.  That's only .1 Amps more than points.

I use 14 Volts for the points because the kill switch typically drops about .5 Volt. The transistor in the PAMCO, as in all electronic ignitions, drops about 1.2 Volts so I use 14.5 - 1.2 - .5 = 12.8 Volts for the PAMCO.

[Bailgang]

Thanks for the info Pete.

[danfr]

What is the resistance on the primary of those coils?
If it is not 5 ohms you killswitch will eventually get fried if you do not use resistors to up the resistance on the coil primaries.

The stock points coil has a primary resistance of 4.5 Ohms so when the coil is on, the current would be 14/4.5 = 3.1 Amps, but the coil is only on for slightly more than half the time with a 190 degree dwell angle, so the average current is 190/360 = .53 X 3.1 = 1.64 Amps. The average current is what would affect the contacts of the kill switch, not the peak current.

The 17-6903 "Ultimate" coil has a resistance of 2.5 Ohms, so its peak current is 12.8/2.5 = 5.12 Amps but the PAMCO rotor has a 120 degree dwell angle so the coil is only on for 120/360 = .33 of the time so the average current is .33 X 5.12 = 1.69 Amps

However, in both cases, there are two coils powered by the same kill switch, so the average current that the kill switch sees is 1.64 X 2 = 3.28 Amps for points and 1.69 X 2 = 3.38 Amps for the PAMCO.  That's only .1 Amps more than points.

I use 14 Volts for the points because the kill switch typically drops about .5 Volt. The transistor in the PAMCO, as in all electronic ignitions, drops about 1.2 Volts so I use 14.5 - 1.2 - .5 = 12.8 Volts for the PAMCO.

I know people are running coil power through the kill switch, but couldn't I run the power to the Pamco through the kill switch. With such a low draw (13mA) it would be a lot easier on the switch.