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Discussion Starter #1 (Edited)
Generalized No-Crank Diagnostic Procedure.
by Wade Nelson

Start by checking battery voltage. Should be 12.5 or above. If below 12.0 volts chances are no amount of recharging will 'cure' it. Take it to the auto parts / battery store and have it LOAD tested.

A battery is like a swimming pool. As it ages, it fills with silt. Not only does it lose capacity but the pipes ALSO clog up so it takes longer (and more alternator effort) to fill and drain.

A LOAD test will apply a load similar to what the starter pulls, and SEE how far down the voltage drops. A poor man's load test is turning on the auto headlights while cranking; if they dim appreciably; you probalby need a new battery. SOME motorcycles turn OFF the headlight WHILE cranking to maximize power available to the starter.

A battery that is 12.6 volts or above is fully charged, 12.3 volts is 50% discharged, 12.1 is 90+ % discharged. Sitting discharged for days or weeks is the fasted way to KILL a battery.

Bottom line: You can't trust ANY electrical testing on a car OR bike until you have a KNOWN GOOD battery to work with.

Now, on to the testing:

Does your headlight illuminate when you turn on the ignition?

No. Check / Replace Main fuse, Headlight work now?

No: Remove and clean battery terminal and cables with baking soda, unbolt main ground from frame, clean to bare metal with sanddpaper, re--attach.

Does headlight illuminate now? Yes - Continue.

No? Diagnose ignition switch. (or replace failed headlight!!!

With bike in Neutral, on center stand (or both) AND both ignition AND kill switch off, jump from B+ (battery positive terminal) to main post on starter. Does starter spin?

NO? Remove and bench test starter.

Yes? Same precautions as above. Jump from B+ to start terminal on starter solenoid.. Does starter spin?

No? Remove and bench test solenoid IF it is integral to the starter.

No? Check solenoid inputs from kickstand switch, neutral safety, kill switch

MOST automotive/mc starters have three connections. One goes directly to the battery positive terminal. It is always HOT, energized, a meter should show 12V there ALL the time. The 2nd, LARGE one, goes INSIDE the starter to the brushes and coils. The 3rd, LITTLE one, usually comes from the starter switch. When 12V is applied to the 3rd one, the SOLENOID is engaged and connects the B+ terminal to the INSIDE connection.

On MANY starters the solenoid is built in, or on, a second little "tube." Older cars/bikes may have a separate starter relay.

Check solenoid input frrom starter switch and make sure it is getting 12v when you press the starter button.

DO NOT connect automotive battery charger on 100+ AMP "Engine Start" position to jump start MC. Result? Fried wires, fuses, generator, stator...

I'm sure I'll think of more to add and correcctions but this will get U started diagnosing a no-crank..

LEVEL 2 -- Voltage Drop tests.

Put red lead of multimeter on B+, black lead on starter main post. Standard precautions apply - neutral or center stand (or both) , but start/run switch to run.

Press start button. If more than .5 volts (positive OR negative) then bad or dirty or loose B+ connection at battery or starter end or chafed cable

Move black lead to start input on start solenoid.

Press start button. Measure .5V or less otherwise start switch is bad, dirty or worn contacts

With Voltage DROP testing what you are doing is seeing, under LOAD, whether the wires, switches, contacts, connectors are CAPABLE of carrying sufficient current to engage the solenoid and spin the starter. Say you've got a main positive battery cable and all the strands of wire are broken except 1-2. You have CONTINUITY, but a HUGE voltage drop will occur when you try and engage the starter as all that current tries to scurry through those remaining strands. So you're finding frayed wires, dirty contacts, corroded connectors, etc. by MEASURING the VOLTAGE DROP they induce in the circuit WHEN a full-current load is attempted.

Starter RELAYS often have multiple inputs, both from the starter BUTTON and SAFETY inputs such as neutral safety, kickstand switch, kill switch, etc. If any of these is NOT either properly GROUNDED or connected to 12V it won't engage the starter solenoid. Every one is different, you may need a wiring diagram if your STARTER SOLENOID does NOT receive 12V when you press the starter button. And I THINK some MC solenoids have a safety input directly on them as well. Anyone?

Hope this helps! (HTL)

Since "No Cranks" seem to come up ALL the time, in the interest of possibly making this a STICKY, can anyone spot any tests/steps I missed, or suggest any additional tests/steps to make the diagnosis tree more thorough?

Clarifications, re-write WELCOME.

Thanks, WN.

H
 

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It also might help to know that [at least in the case of Honda] that certain color wires only have certain functions and that Honda kept the function of the wires pretty much constant within the same color wire. I had a [main]fuse that blew each and every time the ignition switch was turned on. By disconnecting wires from the switch one at a time, it became evident that the black wire was the problem. By using the Honda Wiring Color Codes [that is what you google to find the chart] The chart described just four places the switch sent the current from that color wire.. After two more lost fuses, I located the problem by disconnecting the wire at the shorted out voltage regulator.http://www.vsource.org/VFR-RVF_files/HondaWireColors.htm. This is one chart,but there are others.

I have also found it to be very helpful to have some test leads with alligator clips on each end. You can add power or ground a single component to see if it is the component itself or some other failure. As an added precaution against overheating the wiring,I have a fuse holder incorporated in the jump wire. I use from 5 to 15 amp fuses,depending on the application. The heaviest jump wire I have is made from all 3 wires of an outdoor power cord stuffed into a big alligator clip, and that will crank and start a CB750 Honda

Take the time to learn voltage drop testing. It has improved my life a bunch. My suggestions here do not replace drop testing, but are to be used in conjunction with it.
 

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That's a pretty good overall general guide. Good job, Wade.

Some bikes have slightly different starting circuits so they can have slightly easier checks if you're familiar with them, or completely harder checks if you're not.
 
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