Hello, I’ve been working on my rd for the past year and stumble upon a problem with ignition. I installed a Newtronics ignition on it, the bike runs fine for abou 30 min but always and up draining all the battery, I switched the battery for a bigger one (12ah) but know it runs for 45 min. At idle the meter reads 12.2v but at 5000 rpm it drops to 8v and the higher the rpm goes down goes the voltage. I’m using a ngk coil, used on small engine cars, is a big coil for the size of the engine but I don’t know if this could be the problem, I even tried to still some of the energy of the lights back to the battery using diods but still losing a lot of voltage on high rpm . If you guys have any info that could help I highly appreciate!
Rd350 74 electronic ignition battery drain
- Thread starter Celso
- Start date
First thing to test would be the stator.
There will be three white wires from the alternator and you'll want to measure resistance between each of them (three different readings). You should get a fairly low reading of around one or two Ohms.
Next, test resistance between each of the three white wires and ground. You should get an Open Line reading which indicates there is no continuity to ground.
Finally, if both of those tests are good, you'll want to start the bike and keep the alternator disconnected. Read AC voltage between each of the white wires and you should see around 20V at idle and rising up to 60V by the time you hit about 4000 or 5000 RPM.
There will be three white wires from the alternator and you'll want to measure resistance between each of them (three different readings). You should get a fairly low reading of around one or two Ohms.
Next, test resistance between each of the three white wires and ground. You should get an Open Line reading which indicates there is no continuity to ground.
Finally, if both of those tests are good, you'll want to start the bike and keep the alternator disconnected. Read AC voltage between each of the white wires and you should see around 20V at idle and rising up to 60V by the time you hit about 4000 or 5000 RPM.
crazypj
Split personality, I fake being smart
More likely a faulty R/R. Should be permanent magnet generator. Stator's were pretty good on the RD250/350/400 twins. If I remember right you will have about 16AC volts no load at idle and around 90v AC no load at 5,000rpm. . You should be able to find specs relatively easy If you need to remove rotor, get the correct puller or you will break it. Get some freeze spray while your at it. Every single one of those I've done has been crazy tight. I had one motor in a freezer overnight, with flywheel puller attached. Pulled motor out of freezer next morning, heated puller and flywheel shot across the workshop and through a 1/4" plywood panel 25~39 ft away.. I rebuilt quite a few RD cranks while working at dealers 
I also purchased a Newtronic for a CB360 and the replacement rotor is incorrect - you may have the same issue if everything else checks out OK and the bike chargwed OK before altering the ignition .
Using the supplied rotor would give a dwell angle of nearly 330 degrees at the camshaft, the honda original design is such that the dwell is less than the 90 degrees at the cam between firing the left and right cylinders (checked by re-installing the original points plate and rotor cam) so in my case using the supplied new rotor I would have been drawing twice the current for nearly 4 times as long as intended for the electrical system. As the coils draw around 36 watts each you can see how this could quickly cause a problem.
Not sure on the firing angles of you bike but it might be worth checking the supplied rotor matches the dwell of the original system.
You also state you are using a NGK coil, what is the primary resistance? I believe your bike should be originally be 4.4ohm, if the replacement coil was designed to be used with a current limiting driver it may be very low resistance and draw a lot of current in this application.
Using the supplied rotor would give a dwell angle of nearly 330 degrees at the camshaft, the honda original design is such that the dwell is less than the 90 degrees at the cam between firing the left and right cylinders (checked by re-installing the original points plate and rotor cam) so in my case using the supplied new rotor I would have been drawing twice the current for nearly 4 times as long as intended for the electrical system. As the coils draw around 36 watts each you can see how this could quickly cause a problem.
Not sure on the firing angles of you bike but it might be worth checking the supplied rotor matches the dwell of the original system.
You also state you are using a NGK coil, what is the primary resistance? I believe your bike should be originally be 4.4ohm, if the replacement coil was designed to be used with a current limiting driver it may be very low resistance and draw a lot of current in this application.
Sonrier and PJ are correct. The problem is that the bike is not charging the battery and that's the system to be fixed. It could be a fault in the stator or a broken lead, but regulator or rectifier issues are at least as likely. Get a factory service manual so you understand the system and test as discussed by those 2 wise men.
crazypj
Split personality, I fake being smart
Just remembered something. Remove the generator/sprocket cover and check you didn't pinch the wires, it was very common fault on just about everything at one time or other.The other area to check will be where stator wires pass behind sprocket to come out of case. If you fit an o-ring chain it's wider than stock it rubs on things it shouldn't
