Ignition Problem after Engine Swap

[Demosthine]

Ok guys, I've done a complete engine swap and am down to the ignition problems. As of last night, the bike was jumped from my truck battery (without truck on) and I could get the engine to turn over. I had absolutely no spark, though. So I started diagnosing the spark issue this morning.

When I went to start her, using the same jumper method above, the voltage drops to a dead zero after I turn the key to on. It immediately jumps back up into the right level with the key off. Any ideas? Never had this happen.

[SovietAd]

I'm no mechanic, but I know a little about electronics, and it sounds like you have something that is activated by the key that is shorting. Double check the wiring one everything that connects to the engine, you can ignore any grounds other than when they cross non grounded wire, and replace any wires that appear worn or even slightly damaged.

Chances are pretty good that some wires got crossed or damaged and when the key turns on, the power instantly grounds to the frame or a grounding wire (not sure if the frames are grounded to the battery on these bikes, or bikes at all.)

[tcanthonyii]

What bike? What year? What CC???

[John Hopkins]

Originally Posted by SovietAdmin

I'm no mechanic, but I know a little about electronics, and it sounds like you have something that is activated by the key that is shorting. Double check the wiring one everything that connects to the engine, you can ignore any grounds other than when they cross non grounded wire, and replace any wires that appear worn or even slightly damaged.

Chances are pretty good that some wires got crossed or damaged and when the key turns on, the power instantly grounds to the frame or a grounding wire (not sure if the frames are grounded to the battery on these bikes, or bikes at all.)

Don't ignore any grounds, you may have put the wrong wire to ground...I would remove all ground wires that you have touched, leave them disconnected, then replace just one..try the bike again...then connect another until it shorts when you switch on the ignition..the wire you connect to make it short is the circuit that you have to trace..

If the fault persists with all the ground wires disconnected you may have trapped a 12v wire between the gngine and frame as you reassembled the bike and the weight of the engine has crushed the insulation.

John.

[Schattenreiter]

If you have voltage at the battery with the cables on and it drops to zero when you turn the key on chances are you have a bad ground or hot connection. Where are you checking voltage exactly i.e. directly on the battery post or on the cable at the post? It makes a difference. Check voltage at the jumper cables. Then at the battery post. The move out from the battery. If it is a bad connection then the cables from your truck should hold voltage when the key is on. If not the problem is the cable connection. Keep checking until you find where the voltage holds and then where it doesn't.

Your problem is not likely to be a short to ground because if it was when the key is turned on something would fry(provided your truck battery is good.

[SovietAd]

Originally Posted by John Hopkins

Don't ignore any grounds, you may have put the wrong wire to ground...I would remove all ground wires that you have touched, leave them disconnected, then replace just one..try the bike again...then connect another until it shorts when you switch on the ignition..the wire you connect to make it short is the circuit that you have to trace..

If the fault persists with all the ground wires disconnected you may have trapped a 12v wire between the gngine and frame as you reassembled the bike and the weight of the engine has crushed the insulation.

John.

I meant that as "ignore anything that clearly is suppose to be a ground." If he is chasing the live wires, he'll find where something wasn't hooked up right, though your solution would definitely be faster!