Topic: Coil compatability???

[cafedreamer]

I just purchased a 1978 CB 750F and the coils are bad, one is cracked.  I was given a newer set of coils and wires to replace the old ones but I am not sure they are for my bike.  The numbers on the coils are

Old # DW82-TR1

New # FL703-12v47
           FL703-12v79

If anyone knows if I can use thes coils please let me know. 

Thanks

[Lumbee]

...I think one way would be to test the resistance of the coils you have, and compare that to those of the stock coils.  I wan to say its something like 25olms???  Some one will correct me if I'm wrong.  You'v still got one good coil, compare the resistance in that one to the newer ones you have...

[eldar]

Stock coils are 5 ohm for the 78. now going to the 79,  I think they are 3 ohm. Our coils have non-removable wires. If you can remove the wires on the coils you have now, I would say they are from a later model. There have been many here that have put the lower ohm coils on with no trouble. Supposedly the points wear out faster but I dont know. I am looking to get the hotter coils to and will know more later this summer but notlike that will help now

[SteveD CB500F]

People here have used CB750/900 DOHC coils as they have removable wires and there is someone here using VFR coils - it's a matter of fabbing a mounting bracket.

Consider the poor ignition system - designed for 5 ohm coils (2.4A) and subjected to 3 ohm coils (4A).  Check out the various Dyna threads that go into the ignition and coil question in some depth. The Dyna S replaces the points completely, thereby removing the timing/wear issue.

[cafedreamer]

The wires are attached to the coils.  I was told they were for a CB750 but I didn't know if model differences would cause me not to be able to use them.  I can't test resistance yet as the battery is on a the charger.  As soon as its done I'm gonna put the battery back in, hook up the newer coils and see what happens. 

[Lumbee]

...you don't need the battery to test resistance.  Hook one lead to the wire that goes to the points, and the other inside the plug cap.  Not sure what reading you should get...someone will chime in with the answer...

[SteveD CB500F]

There is no (DC) connection between the primary and secondary windings.

As before, primary (points side) should be 5 ohms, secondary about 25k ohms(?)

[Lumbee]

...thats it...I knew I pulled the "25" I mentioned from somewhere...when I tested my coils it was 25 ohms from cap to cap on each coil...

[DrMark]

I recently replaced my stock 550 coils with a set of cb900 coils I got off of EBAY. I only had to turn the mounting bracket over and they fit great....put new connectors on....And I was out the door in 90 mins. Also mounted new wires and caps...total cost in parts....Coils=$15, Wire=1$ per foot, NGK caps= $2.50 each....Hope this helps.