One side of JDX8 not detonating

[kiedro44]

I put new seals and gaskets into a 73 JDX8 motor that was in good condition; probably only 800 miles on it and it looked really clean inside. While still on the bench, I noticed it had weak and missing spark on the clutch side cylinder. When I got it back in the sled and fired it up without a muffler on, the left jug stayed cold and dripped gas mix out it's exhaust port. So, I pulled the plug on that dead side and then ran the engine(off the good single) to check for spark. As the motor idled, I held the wire and grounded the plug out to the motor and observed significant regular spark, although I'm not sure it was all that strong. This motor wants to run as a twin but where do I start in order to get the left side to detonate? I noticed that one of the condensers appeared to have been replaced while I had the flywheel off earlier. I've tried new ignition coils(the ones outside on the motor) but when pulling it over by hand, these did not seem to make any spark improvement on the side in question. It has newer NGK plug wires and boots. Points had looked clean and seated tight and flat, so I did not "file" them. So does anyone have a idea what is causing the lack of detonation? How do I test? I've read the FAQs but am not sure about this. THANKS!

[400brian]

First swap the two feed wires to the external coils and pull it over with the plugs out, to see if the problem switches sides. If the problem switches sides when you swap the wires, then the issue is under the flywheel. If it does not, then the issue is external.

My X8 did this when I first got it, and it turned out to be a bad plug right out of the box. Under the flywheel, you could have a bad point ( needs cleaning or wore out), condenser, ignition coil, or a wire grounding out.

[JD600]

Just a few other questions, how many thousandths BTDC are your points opening, and what is your gap? Sounds to me like one side isn't opening up completely. If you put a new seal in it, everything needs to be reset per the service manual since the stator has been removed.

DE

[JDT]

Ah, the dreaded "no spark under compression gremlin".

Sounds like a bad plug right out of the box.

But flip flop coils like Brian suggested as it is a 5 sec test.

You could also swap the spark plugs from side to side and see what happens.

And Dustins suggestion to reckeck the stator is important.

Hey did you have good spark on both sides before teardown? Did it run?

[kiedro44]

Thanks for the replies. When I got the sled it ran, and had a lot of grime in the engine compartment(it has a leak around the Y pipe/muffler joint) and I didn't think too much about it since I was seeing some spark on both sides. So I suppose it has had this problem for a while based on the greasy evidence. I don't know much about resetting the ignition. I'll look it up in the manual.

[JDT]

There you go.

A wise man once said "buy the book first".