What is wrong with my motorcycle?
June 3, 2009 11:28 PM Subscribe
The starter on my 1982 Kawasaki KZ 750 LTD runs continuously when the battery is connected. I've checked the kill switch and the ignition and neither seem to be shorting out. What should i check next?
The bike starts fine if i jumper the battery to the +/- hookups and runs great once it is started. The problem is that anytime the battery terminals are connected, no matter what position the key or the kill switch are in, the starter runs.
i've checked and cleaned the kill switch and the key ignition and most of the wiring and nothing jumps out at me as being broken. the previous owner said he couldn't get it started and he suspected a short.
Additionally, the problem is not solved when the ignition and the kill switch are disconnected completely.
The bike starts fine if i jumper the battery to the +/- hookups and runs great once it is started. The problem is that anytime the battery terminals are connected, no matter what position the key or the kill switch are in, the starter runs.
i've checked and cleaned the kill switch and the key ignition and most of the wiring and nothing jumps out at me as being broken. the previous owner said he couldn't get it started and he suspected a short.
Additionally, the problem is not solved when the ignition and the kill switch are disconnected completely.
Best answer: Yup, 99% of the time it's a jammed starter solenoid or sticking solenoid contacts inside the starter. The other 1% of the time it's a broken starter switch that's not releasing.
Your starter should have 2 cables going to it: a honking big one going to the battery, and a much smaller one coming from the switch. If you've got a meter or testlamp, hook it up to the small one (& ground, of course) - if it comes on when you press the starter switch & goes out when you release it, it's a sticking solenoid; if not, it's the starter switch.
posted by Pinback at 1:48 AM on June 4, 2009
Your starter should have 2 cables going to it: a honking big one going to the battery, and a much smaller one coming from the switch. If you've got a meter or testlamp, hook it up to the small one (& ground, of course) - if it comes on when you press the starter switch & goes out when you release it, it's a sticking solenoid; if not, it's the starter switch.
posted by Pinback at 1:48 AM on June 4, 2009
All of my motorcycle experience is with mid-'70's Hondas, so I don't even know where they put the solenoid on your bike, but that's definitely what I'd check. On my first bike, which wasn't quite as old when I had it as yours is now, the solenoid contacts wore out to the point that they arc-welded themselves together.
On my bikes the solenoid was mounted under one of the side covers, near the battery. The fat red wire from the positive battery terminal should lead directly to that solenoid. The other large terminal on the solenoid will have another cable that goes to the starter motor. If there's continuity across those two larger solenoid terminals when the battery is disconnected, the solenoid is jammed / welded / otherwise shot.
posted by jon1270 at 2:48 AM on June 4, 2009
On my bikes the solenoid was mounted under one of the side covers, near the battery. The fat red wire from the positive battery terminal should lead directly to that solenoid. The other large terminal on the solenoid will have another cable that goes to the starter motor. If there's continuity across those two larger solenoid terminals when the battery is disconnected, the solenoid is jammed / welded / otherwise shot.
posted by jon1270 at 2:48 AM on June 4, 2009
There's a chance that you can free up your stuck soleniod by tapping it with a hammer. That way, you've got a running bike while you get your new parts together.
When you examine your starter, make sure there's nothing shorting the signal and load hot terminals of the solenoid together. It was smart to rule the ignition switch out by removing it, but there's still some potential for the signal side of the relay to be shorted to power at another point (even though it's much less likely than being stuck mechanically). To check, you could simply disconnect the smaller wire that runs to the starter solenoid. If it stops running, then you've got a short to power in that circuit.
posted by Jon-o at 5:00 AM on June 4, 2009
When you examine your starter, make sure there's nothing shorting the signal and load hot terminals of the solenoid together. It was smart to rule the ignition switch out by removing it, but there's still some potential for the signal side of the relay to be shorted to power at another point (even though it's much less likely than being stuck mechanically). To check, you could simply disconnect the smaller wire that runs to the starter solenoid. If it stops running, then you've got a short to power in that circuit.
posted by Jon-o at 5:00 AM on June 4, 2009
One more vote for the starter solenoid. I've never owned a KZ, but I've had failed starter solenoids on a bunch of cars and bikes -- it's really common, and they either fail such that the vehicle won't start, or they do what you are experiencing, sticking closed and keeping the starter whirring.
posted by Forktine at 5:49 AM on June 4, 2009
posted by Forktine at 5:49 AM on June 4, 2009
I don't even know where they put the solenoid on your bike
in case you haven't found it yet, and if the 750 is put together at all like the 250 (which it probably would be) you'd be looking for something out the front of the engine, roughly the shape of the inner cardboard core of a toilet paper roll, only about double the size. it'd be down low, between the engine & the exhaust tubes.
posted by UbuRoivas at 5:58 AM on June 4, 2009
in case you haven't found it yet, and if the 750 is put together at all like the 250 (which it probably would be) you'd be looking for something out the front of the engine, roughly the shape of the inner cardboard core of a toilet paper roll, only about double the size. it'd be down low, between the engine & the exhaust tubes.
posted by UbuRoivas at 5:58 AM on June 4, 2009
Best answer: This page (about two thirds down the page) has links to what looks to be a fairly complete parts manual, including electrical diagrams, for the big KZs. What we're calling the "starter solenoid" is what the diagram calls the "starter relay" -- same thing, different name.
posted by Forktine at 6:58 AM on June 4, 2009
posted by Forktine at 6:58 AM on June 4, 2009
This thread is closed to new comments.
starters require a lot of (electrical) juice, so there's normally a direct high-tension circuit from the battery (on cars, bikes, whatever).
when you hit the ignition, a lesser electrical charge flows through the ignition circuit and engages a solenoid, which simultaneously:
* allows current to pass through the more heavy-duty circuit that i mentioned before, and
* physically pushes a cog so that it engages with the engine.
my guess is that the solenoid is jammed in the "on / start" position, so your heavy-duty circuit from your battery is permanently open. you'd probably need to remove the starter & open it up, to see if any moving parts are stuck. if you're lucky, you *might* be able to get away with a gentle tap or two with a rubber mallet on the starter, but don't blame me if you break anything.
posted by UbuRoivas at 12:23 AM on June 4, 2009