This thread contains information about K bike the starter motor, starter circuitry and starter "sprag."
The Starter MotorThe picture below is a K bike starter motor. The same starter motor is used on all classic K bikes (and the K1200RS too.) Its part number is 12411459007.
Here's the parts diagram for it.
It's kind of hard to see it in the picture below but it's located inboard of the coils to the left of the alternator. The rear of it mounts to the top front left of the transmission housing via two M6x25 Allen cap bolts.
Starter Circuitry
Below is an example of the wiring for the starter.
In order for the start button to turn on the starter the ignition must be turned on and the start button must have power from one of two sources: either a) the clutch switch when the clutch is pulled in or b) the gear indicator circuitry in the instrument cluster when the bike is in neutral. (The two black/green wires in the diagram above.)
When you hit the start button it energizes the black/yellow wire to trigger the starter relay which provides power to the starter. The power to the starter relay also triggers the load shedding relay while the starter is running. The load shedding relay turns off the headlight and a few other things so that more power is available for the starter and other electronics when starting the bike.
The starter relay is located in right rear corner of the black plastic relay box under the rear of the gas tank. The starter relay looks like this:
Note that the exposed incoming power lead for the starter relay is always "hot" and directly connected to the positive battery terminal (without a fuse) so if you're working near there then disconnect the battery ahead of time or be VERY careful not to let anything short to it.
The Starter Sprag
K bikes do not have a solenoid for the starter motor like a lot of car engines do. Instead it turns the engine by way of a one-way set of gears commonly referred to as the
starter sprag. The starter sprag is located between the front of the bellhousing and the engine block.
Here's what the starter sprag assembly looks like:
And here are the one way gears in the starter sprag that engage to turn the engine over when the starter motor spins the sprag.
Starter Troubleshooting:Starter spins but motor doesn't turn over: On some bikes, as the miles rack up, oil gunk build-up will keep the sprag from engaging so that the starter motor just spins without out turning the engine over. There's a few possible remedies for this:
1 - Put the bike in gear and rock it backwards to see if that will cause the sprag to engage.
2 - Run some Rislone or other engine oil "cleaner" or engine flush to see if that will break down the oil gunk and make the problem go away.
3 - Remove the bellhousing and clean or replace the starter sprag. (This is a MAJOR endeavor.)
Starter keeps turning after start button is released: The typical cause of this is a low battery. What happens is that the contacts in the starter relay don't fully connect, a spark forms between them and "welds" the contacts together so that they do not disconnect when the relay is de-energized.
Sometimes a sharp rap on the right rear of the relay box will cause the contacts to disengage. Or you may need to take the starter relay apart and clean the contacts. Worst case you'll need to replace the starter relay.
On two valve K bikes and early (ABS I) four valve K bikes the easiest way to stop the starter is to disconnect the main ground which is located on the left side of the transmission above the shift lever.
Starter button doesn't work: This is typically caused by either the starter button contacts being dirty/corroded or a lack of power to the start button.
If you remove the Phillips screw from the bottom middle of the right hand combination switch on the handlebars then you can access the starter button contacts from behind. Remove the E-clip from behind that holds the start/kill switch assembly in the combination switch. You can then pull the switch apart and access the contacts to clean them. You might want to do this off-bike or have a shoebox underneath as there are some little parts and springs in there that are easily lost if you're not careful.
If your gear indicator is bad and/or not illuminating the green "N" light in the instrument cluster then the only way to start the bike is to pull in the clutch. However, if your clutch lever switch goes bad (which they do) then you won't have any way to start the bike. If you're sure that the switch has gone bad then cut the wiring to it and short the two wires to each other. Once you've done this make sure that those wires don't short to anything as they are "hot." Then replace the switch when you get home.
edit by motobrick johnny 9-29-13 added snowbums piece...edit by scott_ 10-12-13 added missing pictures...Starter Sprag Clutch Problems ~ author robert fleischer K100, K1100, and K1200, all versions.
