rediculous backfire, why?

i have a 1975 kz with 1980 z1r engine in. i took the motor out to have something fixed. motor was drained of its oil and upside down for a couple of day. i put motor back in when it was fixed and now i cant get it to start. it will turn over and will back fire out of the exhaust. it is super loup when it pops. thought it was carb issue, so i rebiult them and it still pops really loud and now i got fire comin from the carbs. i did nothing to the motor internally or carbs. what is wrong with my bike? any light shed on this would greatly be appreciated!

sounds like your timing is off. Check--using the manual the position of cams--using the marks on the cams to the top of the cam cover when the crankshaft is at the correct timing mark TDC

Sounds like you have you coils/plug wires crossed. :ohmy:

If not already done, would also check valve clearances, especially intakes, as a too tight intake valve can allow backfire through the carb.

Good Luck!

taildragger1197 wrote:

Sounds like you have you coils/plug wires crossed. :ohmy:

Agreed. These are the symptoms of ignition being 180 degees off (ie cylinders 1&4 are firing when 2&3 should be firing and vice versa. Try switching the wires at the coil.

Usually, left coil with small black wire fires both outside plugs, and right coil with small green wire fires both inside plugs.

Good Luck!

I'm with the others... Bet a Dr Pepper coil wires are crossed!