Sled engine,spark goes away?

[Bullnerd]

I've been messing around with a yamaha v-max 600 sled engine on the bench.Sometime before i die i'm going to put it in a chassis.
The problem is when i crank the engine with the starter while grounding a plug,i see a nice bright,fat spark,but then it stops.It sparks right when the engine starts to crank but then nothing.Same if i pull the pull starter.
I'll put up a wire diagram as soon as i scan it.
I'm still learning about sled engines,is this a common pulse coil or magneto problem?

[nutz4sand]

You still got the key switch? The handle bar switch too? Triple sure the grounds are all good? Really tough in the sled and tougher out of it.

I got the same motor sitting here but I got a wacked up chassis for "test stand".

[Bullnerd]

No key switch.
No handlebar switch.
I THINK all the grounds are good,they are all grounded to the block in the same spot.I tried to ground every thing that is grounded on the schematic.

The one wire i am not sure about goes to the "engine stop" switch.The schematic shows it grounded through the main switch and also through the engine stop switch?

[ruthlessxbeastx]

sounds like you have a common ground. well in car audio i know it matters and on my honda odyssey i know it does. i had everything grounded to the same spot and my odyssey i got a single spark nothing else. so try splitting up your grounds [frame, bech, ect]

[nutz4sand]

Check this.

The Coil bolts to the top of the airbox. Being the box is plastic it of course gets NO ground thru it. There is a black wire with a flat disc on the end and it should ONLY touch the coils center laminted bars. No other ground.

The coil ground is coming out the same part of the loom as the orange coil power wires is. Try it ONLY connected to the coils center metal laminate core.

[Bugpac]

Most sleds have a safety switch on the thumb throttle as well, what yr is that thing?

[nutz4sand]

Thats what I meant by the handlebar switch. I guess I could have been more clear. That model engine was middle of 93-94 to middle 96-97

[Bullnerd]

Its a 94.
Carb switch is grounded.
Throttle switch is grounded.
You might be on to something nutz,i do have the black wires going to the ends of the coil,but i also have a ground strap going from the coil end to the block.
I'll try that when i get home.

[Bullnerd]

1994 v-max 600 wiring diagram

[Bullnerd]

Nope!I isolated the coil grounds,no dice.