Wont Start back up, shotgun blast sound. HELP!

[UntappedMana]

Hey Hivemind,
So after the winter, I ripped my carbs out, cleaned em real good, took EVERYTHING out, cleaned, put back correctly, synced to factory settings, but two full turn on the fuel screws instead of 1 and a half, because everyone and their mother seems to say that 2 is better.
Anyways, its all hooked back up, I tripe checked everything more than once, referring to the owners manual and on this forum. Now, it turns over like a bandit, sounds like its just about to grab, but wont fire, choked or not. After a few trys, I get a very very loud bang, almost like a gunshot, out of the tailpipe. I seem to have fuel, I check the plugs and I have spark, yet the tips seem to be dark. the plugs were changed last year.

Where do I start? im dying not being able to ride, and weve had a solid 2 weeks of riding so far up in NH this year.

Thanks!
-Frank

[Kreylyn]

Is this a US model bike? If yes, then 2.5 turns... not 2.

If this is a UK model bike, it's 1.5 turns... on the a/f screws.

Check your coils are correctly plugged on the right plugs... left is white signal wire, 1 & 4 for the plugs.

[Phantom552]

Shotgun blast sound would likely be unburned fuel igniting in the tail pipe. Make sure you set the floats correctly and did a bench sync as described in Carbs 101. As Krey said, US bikes like 2.5 turns typically. UK models like 1.5. Since you presumably have air and fuel, you likely lack ignition. Pull the plugs, check their condition. Crank it over once with the plugs out to expel any fuel pooled in the cylinders. Reinstall plugs, double check coil and plug wiring for proper positioning, as Krey decribed. Add fuel or hook up a temporary fuel tank and try again.

[UntappedMana]

Its US Model. 95 Katana 750. I did pull the plugs. Little wet and darkish. Not oily though. So likely Gas. I'm going to start with changing the plugs after work today. And yea, the firing order on the spark plugs are correct. I triple checked that more than once. I'll do another half turn on each screw, but i still feel like if it was running a bit lean or rich, it woulds still somewhat fire up.