Why Does My Bike Pop When I Start It

[Clarkkk]

This really freaked me out! Here’s the video https://youtube.com/shorts/4yIa2KqIB9g?feature=share

[47str8leg]

This really freaked me out! Here’s the video https://youtube.com/shorts/4yIa2KqIB9g?feature=share

Can’t even tell where its coming from.
Maybe the exhaust on the other side of the bike ?
Show a picture of the opposite side to see the exhaust. Could be the timing is off and the exhaust valve is not fully closed on the compression stroke.

[EVILBLACKSABRE]

I don't really know squat about Harleys, but I can't help but wonder if it's some kind of electrical discharge.

Electrical discharges/shorts will definitely make a "POP" sound, along with a flash.

Whatever it is, it's not good. I definitely wouldn't ride it until you get it fixed.

[armand]

I see the flash coming out behind and below the engine. What is down there? Exhaust?

[BlackCloudSalvage]

Definitely looks and sounds like electrical. What you got down hiding down there? Will it do it repeatedly or did it just blow once?
Sounds like its happening before engine even begins to fire. Doesn't seem like gas / engine pop.

[47str8leg]

Definitely looks and sounds like electrical. What you got down hiding down there? Will it do it repeatedly or did it just blow once?
Sounds like its happening before engine even begins to fire. Doesn't seem like gas / engine pop.

Definitely just fired in the video. I thought it might be electrical also but wanted to see where the pipes dumped out on the opposite side.
Thats a hell of a short. Would be coming from the starter area most likely if it is. Only thing I can think of that would be cranking enough amps to shoot a spark like that.

[BlackCloudSalvage]

And don't you dare leave us hanging after you get this one figured out!!! We want to know!

[7and7is]

I bet you he has either shorty exhaust, or its an exhaust joint thats not sealed tight.

[seaking]

Yeah he's got a lot of gas built up and when it starts it only fires enough to pop, my first bet is electronic ignition going out. If it was hard to get home, but made it? It's probably the module. I always have that happen when I set the points gap too wide. Then check for proper spark, then wires, coil output, then grounds/reg/battery/electronic ignition is usually the order I'll check.

[47str8leg]

Yeah he's got a lot of gas built up and when it starts it only fires enough to pop, my first bet is electronic ignition going out. If it was hard to get home, but made it? It's probably the module. I always have that happen when I set the points gap too wide. Then check for proper spark, then wires, coil output, then grounds/reg/battery/electronic ignition is usually the order I'll check.

It continues to run until he turns off the key sfter the pop.

[Clarkkk]

This really freaked me out! Here’s the video https://youtube.com/shorts/4yIa2KqIB9g?feature=share

Sorry to leave y’all hangin! But the exhaust is stock!
Just finished the chopper rewiring
Replaced coil, spark plugs, spark plug wires, and ignition module!
Im guessing it’s the timing. Haven’t timed it yet.
But why the weird spark? It’s sparked once (started it two other times and just got a pop) but havent left it running long.