Shoulda added.... Jeff, you were right. Apologies for ever doubting you.
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Cam Chain Guide
- Thread starter NP2650
- Start date
Just a thing I ran across on my SG (tracker) when it did blow a main fuse - the rotor had dropped to ~2 Ohms. I then rewired the bike and had you rewind that rotor. IDK if the Type B regs are ahead of the fuse box, but I suspect they may be
I think they were (on the brown from key switch) on the pre-fuse box models and they may have left that splice there on the fuse box bikes (guessing)Anyway, a similar condition may exist here with that voltage drop - 4.6 Ohm rotor would produce that. But the way the Safety Relay is wired through the Light Checker puzzles me.... The solenoid circuit losing power intermittently - the safety relay is supposed to cut that power when is sees voltage from spinning stator, not vice versa. Perhaps it's an oddity of the light checker failing or.....
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Well, as I said, checking current draw might be more useful in finding out where the power being lost at. Seeing a voltage drop (like you're doing) could be either higher than normal resistance to a component, or that component drawing more current than it's supposed to.... checking to see how much current is being drawn will tell us which it is.
I should have explained a little better....
Let's say for instance you have a voltage drop across a switch. That voltage drop is caused by higher than normal resistance across the contacts inside it.
But.... the higher the resistance, the less current it's able to draw. If that means less current to the starting circuit then yeah, that's a problem.
But if the higher resistance (more voltage drop) is in a circuit that has nothing to do with the starting circuit, it's not gonna have any affect.
On the other hand, a higher than normal current draw anywhere on the bike is gonna affect starting. It's the better way to find out where your power is and isn't going.
Those all look normal..... correct except for the 1A with *all else.* It might be normal or it might be something pulling power that shouldn't be. Off the top of my head I can't think what. Try disconnecting different stuff and see if it goes away. Just thought, were the taillight or indicator light on? That might explain it.
Also, have you had your battery load tested?
Sure they were. My 72 only has 1 20amp fuse for the whole bike.A shorted regulator would blow the 20A main and kill the whole bike. Surely Yamaha wasn't that dumb?
I think you need to investigate this further. In my experience 11.5 volts is more than enough to pull in a 12 volt solenoid.
I think he needs to connect his voltmeter to the coil posts of the solenoid and see what he has when pressing the starter button.
Yep, all the way up to '77 I believe.
But in '78 and '79 they went to the fuse box with 4 fuses. And looking at the diagrams, they put the reg. feed on the 10A Signal fuse... which makes sense because the reg. only draws about 2.5 to 3 amps.
Then in '80, they went with the reg/rec and again... fed it off the 20A main fuse. Makes no sense. If the reg. were to fry, or more importantly, the brown wire rub against something that rubs the insulation off... a fairly common failure mode.... it's gonna blow the main and kill the whole bike, just like it does with your '72. That's crazy. I'ma have to walk home just because the reg. wire shorted? Stupid.
I'm gonna investigate further. When I have time, I'm gonna short the wire at the reg/rec on my '80SG and see if it blows the 20A main. If it does I'm gonna rewire that circuit and add in a 10A fuse just for charging. If it blows, I can still move on down the road 'till the battery gives up.
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So, power to the solenoid comes from R/Y (fuse box) to R/W with the motor off...Motor spins, energizes Y from stator...Safety Relay opens R/W disabling solenoid and energizes L/B and turns headlight on (?).... What's the purpose of R/W routed back to light checker?
Ok, given that peculiarity and the fact you're losing power to the solenoid before Y is energized; points to a problem with the Safety Relay and its switching of the R/W (that emanates from R/Y circuit)
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Be easy enough to make a jumper and go around the safety relay. It's the R/W that feeds the solenoid though. Disregard the red jumper drawn in, it's for something else.
Just jumper the R/W going into and out of the safety relay. It'll bypass it and send power straight to the solenoid.
I have about 11.5 volts at the starter relay. However, when testing this I noticed that the voltage was intermittent. I traced it back to the safety relay, which had constant power going in, but intermittent power going out (and to the starter relay). I popped the casing off the safety relay and checked to see if the relay was activating and cutting the power; it wasn't. So I gave the relay contacts a good cleaning, and for now things seem to be working. Because this was an intermittent issue, only time will tell.
I know I chased down a number of rabbit holes on this, but automotive electronics are not my strong suit. In any event, in doing all this work I learned a lot about how these bikes are wired, etc., so not a total waste of time. Thanks for your patience and all the help.
That education is worth it's weight in gold.
Dirty contacts in the safety relay. That's the cause of my starter issues. Starter works 100% of the time now, and my headlight automatically comes on once the bike is running. I have taken the bike out on several short trips so far and put about 60 miles on it. It seems to run better and better every each time. Time for another one; I would really like to find a decent XS2 that is somewhat close to me (Northern California).
OK, if you want to enable the handlebar on-off headlight switch full time and do away with that headlight auto-on feature, just unplug the blue/black wire that comes out of the starter/headlight safety relay. It's the power out line for the headlight once the relay is tripped. Unplug it and the relay will still be doing it's thing, it's just that it's signal won't go anywhere any more.
