Back fire from Carbon Fouled Spark Plug?

[Vintage Engine Repairs]

Anyone else experienced it? I never thought it could do that, but this coil has timing advance and at low rpm it’s not far off sparking at TDC so I guess weak spark didn’t ignite the charge well and it propagated slowly enough that it was still burning as the piston travelled back down allowing it to shoot back through the transfers?

Anyway, I checked timing via degree wheel and timing light, and was showing 10 degrees BTDC via a drill spinning it, which seems late, but this coil has ignition advance built in so i suppose not. I checked it against another identical coil that had identical timing. Checked the spark arrestor, everything. Till I just realised I had nothing to lose and changed the plug… this is the first time ever that I have had a plug be the reason an engine wouldn’t run let alone back fire and it wasn’t even that carbon fouled.
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[MFV]

I accidentally flooded my 880 the other day and I guess it backfired and just ripped the starter handle out of my hand. Did yours do anything like that?

 

[MFV]

Ok got the video to play doesn’t look like it pulled the handle out of your hand .

 

[Vintage Engine Repairs]

I accidentally flooded my 880 the other day and I guess it backfired and just ripped the starter handle out of my hand. Did yours do anything like that?

This ignition happened after TDC rather than before TDC so it didn’t rip it from my hand.

 

[MFV]

Ok so before TDC is when it rips the handle out of your hand. Pretty violent I won’t make that mistake again.

 

[pioneerguy600]

My gasoline powered air compressor started missing & backfiring when running under load, I pulled the plug and it looked ok, not really dark or dirty at all but the engine would not run smooth or right at all. Since I was in a remote location I did not have my box of spares with me and no spare plugs for these 4 strokes. I took the plug out of my Honda generator and put that back in to the compressor, it started and ran fine again. I did need the generator also to run the circ saws and lights so just for shts and grins I put the plug from the compressor back in the generator and lo and behold the generator would run fine on it, head scratcher, only diff I could come up is the compressor runs under a heavier load than the generator.

 

[buzz sawyer]

I accidentally flooded my 880 the other day and I guess it backfired and just ripped the starter handle out of my hand. Did yours do anything like that?

My Super 1050 did that until I got rid of the aftm chip and went back to points. I still put a snowmobile handle on the starter to use my full hand.

 

[Vintage Engine Repairs]

My gasoline powered air compressor started missing & backfiring when running under load, I pulled the plug and it looked ok, not really dark or dirty at all but the engine would not run smooth or right at all. Since I was in a remote location I did not have my box of spares with me and no spare plugs for these 4 strokes. I took the plug out of my Honda generator and put that back in to the compressor, it started and ran fine again. I did need the generator also to run the circ saws and lights so just for shts and grins I put the plug from the compressor back in the generator and lo and behold the generator would run fine on it, head scratcher, only diff I could come up is the compressor runs under a heavier load than the generator.

Strange Jerry! Thanks for sharing. Nice to know it’s a known thing to an extent.