‘93 G8 with a ‘95 G9 J38 Spark issue

[Sully07]

Ok so I bought this ‘93 G8 a week ago with a locked motor knowing I had a motor out of my ‘95 G9 sitting on the shelf while I tinker with the build. Only thing I saw different between the two is the oil light wire in the G8’s harness I don’t have, and the three wires going into the block had a different style connection. So I cut the connection off the junk motor and wired it to mine, hooked it all up and she stared right up but won’t run.

After checking a few things I checked spark, it only sparks one time when the pedal is first pushed but only when the engine is stopped. If it’s already rolling it won’t. Now before I found my meter today I swapped everything possible minus CDI as I’m not sure where my other one went, anyhow same thing. Pulled the harness apart found nothing, read **** near every threat on this issue and no help but I didn’t see anyone with the same issue exactly. BUT now that I found my meter I’m getting a consistent 11.4-11.7 volts at the plug boot and everywhere from there to the battery which is at 13.1v. Any help is appreciated. This was supposed to be an hour motor swap just to have something to cruise while I’m working on the 9 So much for that!

[crash12888]

I'm stabbing at it but I think you have two of the three wires connected incorrectly, See if you can find the wiring diagram for both carts and check the color of the wires and locations of each.
You might just have two backwards.
\Or you might need to swap in the G9 ignitor.

[Sully07]

I’ll check that possible wire cross, the colors and stripes match but worth a check. I wish I knew where the one from the G9 got off to. Tore it all the way down to be powder coated and it’s the only thing I can’t find, and no it’s not still on the tank, I got excited for a second after looking for it thinkin I left it on but it wasn’t there 🤦🏻*♂️

[Sully07]

Anyone ever tried one of the Amazon or EBay CDI’s? $20-$30 is a long way from $250-$300 I know these carts can be finicky with electronics so I’m hesitant but that’s alotta dough

[crash12888]

Unfortunately, All of the cart electronics are finicky when it comes to aftermarket stuff from overseas. Yamaha is one of the worst about playing nice with other junk.
I'm still leaning toward the wiring schematics showing you the way.

[Sully07]

Figured it out! Came across another thread completely by accident looking browsing big block swap posts for my G9 and had all the information I needed. Turns out the ignition system on a G8 is JF2 amd the G9 engine still had the J38 pulsar coil, flywheel and ignition coil mounted. Swapped them out and had consistent spark immediately. Not sure how to post the screenshot yet as I’m new here but if anyone else Is having this issue try searching G9 engine swap, it’s about halfway down the first page I believe

[raydhd]

You might to look at smallblock's Sticky on engine swaps at the top of the yamaha section here.

[Sully07]

I do believe that’s what I finally stumbled across. Saved the day!

[smallblock450sl]

Glad the post helped a member.