1976 KZ400 Bench Test wiring

Im going to pull the engine from that 1976 KZ400. I want to do a bench test type thing with this and start it on the floor in my kitchen:D Its a points an condenser set up so i thought i would just hook a battery up to the positive lead on the starter and ground negative to the block but i forgot about the coils. Do i need to use the original harness for this or can i just run the points wires up to the coils and still get spark?

Thanks guys,
KT

May test run engine with hot-wire to coil primary.

Disconnect hot-wire when engine isn't running.

Wire from points connects to other coil primary.

The coil primary terminals have no polarity, so it doesn't matter which wire goes to which primary terminal.

See image below.

Good Fortune!

An ignition coil "charges" while its primary winding is grounded through closed points.

When un-grounded by the points opening, the coil "fires" through the plug wires.

Good Fortune!

Shweet, I'll probably have that engine out sometime soon.
Thanks man,
KT

ok, I have that motor sitting on one of those mover's dollies in my garage. I have the points plugged into the coil and the plug wires hooked up. The coil is bolted to the valve cover with the mounting braket that would normally bolt it up to the frame. I also have a battery sitting next to the whole thing so as soon as i get some gas ill see if it will fire it up. Do i have to hook up the AC generator to anything, or is it just the coil, points, and a battery? the starter dont work so ill be doing alot of pushing and kicking with my foot and hand on that kicker lever. Also, the left side engine cover didnt have a gasket because somebody with absolutely no mech. knowledge worked on it before i got the bike. So, Water got in there, contaminated the oil and got the magnet, stator (inner and outer stator coils) both rusty as hell and the starter clutch wont engage.. will this ruin a stator or can i just clean everything up as best as possible? I know there was water in the oil because there was about 7 quarts in there.. 4 of them being water (thick white gunk..). should i flush out the motor with something to make sure all of that gunk is out of there? if so, what do i use to flush it out without totally dissasembling anything? I guess usually when something is too good to be true, it really is too good to be true. I did the compression test wrong i think and i got a really good compression reading the first time.. It had no carbs in the manifold boots this time and when i did the test, it only had 90PSI on cylinder 2... Does it need a set of carbs to do it properly? please say yes:D Anyways, ill read your comments tomorrow when im at the garage. Let me know whats up guys..

Would first change oil and filter as usual.

Also sniff and examine old oil to determine if possible whether there's been any fuel contamination into the crankcase, and take corrective action as needed (usually a carb issue).

Until the battery runs down, the engine should run fine without any charging components.

Carbs aren't needed for compression testing.
When fitted, carbs should be held wide-open-throttle during compression testing.

Low compression may result from a too tight valve clearance.

Good Fortune!

I already have the points plugged into the coil so do i just hook up positiive on the battery to the other lead then and ground negative to the block? Im going to get a jug of oil then and pull that filter i guess too. Probably wont run today but it should be up pretty quick here.

Kitten Tooth wrote:

I already have the points plugged into the coil so do i just hook up positiive on the battery to the other lead then and ground negative to the block? Im going to get a jug of oil then and pull that filter i guess too. Probably wont run today but it should be up pretty quick here.

do i just hook up positiive on the battery to the other lead then and ground negative to the block? --- that should do it.

When engine isn't running, the positive from battery should be disconnected. Akin to turning off a standard ignition switch.

Good Fortune!

I dont want to sound like a noob but does the coil have to be grounded to the engine?

Kitten Tooth wrote:

I dont want to sound like a noob but does the coil have to be grounded to the engine?

On that type of system, no, the coil itself does not need to be grounded. However, the primary side of the coil does need to be grounded and ungrounded, through the points as Patton showed above.
The coil sparks from one spark plug wire to the other. On the bike, the plugs are grounded to the engine, but that is incidental. They really don't have to be. The plugs just need a path from ont to the other, and the engine just completes that path. The spark current doesn't actually need to go to ground.



On old cars, the coil body had to be grounded to the engine because on those old car coils, the spark path started in the coil wire, and ended in the coil's body. In order to spark, the coil's body had to be touching the engine.

Kitten Tooth wrote:

...does the coil have to be grounded to the engine?

Edit: loudhvx beat me to the punch!

does the coil have to be grounded to the engine?

Nope.

When charged coil primary winding becomes ungrounded (as points contacts open), high intensity voltage circulates through the secondary loop.

Good Fortune!

Patton wrote:

...When charged coil is ungrounded (as points contacts open), high intensity voltage circulates through the secondary loop....

See illustration in following post.

Good Fortune!