Topic: Wrong coils can I use them?

[XC204]

Quote from: XC204 on March 02, 2020, 06:28:10 pm
Had a little time yesterday evening to do something with the bike so I decided to fit the coils that I got about 8 years ago. The have  wire connection clamps for the plug wires so they can be replaced. Well the wouldn't fit right with the stock mounting brackets so I modified the brackets so the coils would mount from the side of the brackets instead of the top. Yea success! Looked good fit under the tank what more could I ask! Well I decided to measure the coil resistance ......1.5 ohms crap the were supposed to be electrically the same and 1.5 seemed low dang yep wrong on the plus side I would have had to modify the brackets any way for them to fit under the cb650 tank so all is not in vain. Will be ordering new coils.

A question for Honda Man  I did the above and now before I send off for new coils can I use these with resistors ? I don't know the inductance of the primary (can measure at work) nor the minimum time constant needed for max rpm got to look at lobes on rotor ad see how many openings \ revolution  4 or 2 ? Or do I need to bite the bullet and buy new coils I can get high watt resistors no problem. This is from Project Shop CB500 "Free" style by me XC204
Thanks in advance
Gary

[bryanj]

WHAT BIKE generator output varies

[XC204]

Sorry 1973 CB 500 four

[Bodi]

I don't know why alternator output matters ...
These coils are not ideal. 1.5 ohm coils are generally for electronic ignitions. Possibly even for a different type of electronic ignition, with the coil used as a pulse transformer - those types will not work with out Kettering ignition system.
Definitely do not use them connected directly to the points, the high current will destroy the points pretty fast, maybe blow a fuse, and discharge the battery as you ride if they do get the engine running.
If you add a 3 to 4 Ohm resistor in series with each, they might work. I think the spark may be weak, but can't be sure.
I recommend getting the correct resistance coils. The Dyna ones will work well, te mounting is close to stock, and the cables are removable.

[bryanj]

Generator matters because on the 500/550 charging current is minimal and those coils would put the charging negative so you will always flatten the battery. Puting a resistor in is an unwanted heat source so get the correct coils, tesistance is in the manual

[tlbranth]

The GL1000 uses a ballast resistor. The recommended non-honda replacement  is NAPA (Echlin) Ballast Resistor #ICR13. Note that this is a power resistor which might get a tad toasty. If I were you I'd just buy a set of Dynatek 5 ohm coils and their plug wire. That's what I did. Mounting the resistor for the 1.5 ohm coils will be a bit aof a pita.

[XC204]

Yes I'm pretty much on to getting stock coils when I do the calculations at the end of charging up the coil has about 5.2 v and the resistor (3 ohm) about 7.8 v so sparks got to be less than 1\2 power so it looks like new coils. Thanks for the push in the right direction guys

[XC204]

Tlbranth I've got the resistors (50w and an easy way to mount them) but I think it's new coils like you guys said.
Thanks
Gary

[gtmdriver]

The coils should be around 3 ohm. If you use the 1.5 ohm coils the current flowing through the system when the contact breaker points are closed will be double what it should be. This will cause greater arcing and excessive wear.

If you want to use these coils you need 1.5 or 2 ohm ballast resistors in series with the coil supply.