Starting a rusty '82 KZ750

Tvag06 wrote:

TexasKZ wrote: I seriously doubt that the clean air system is the problem. Its sole purpose is to introduce clean, filtered air into the exhaust ports in order to dilute the exhaust gasses so the bike can pass an EPA sniffer test. The most common malfunction is for the vacuum hoses to split, causing two cylinders to have a lean mixture. That doesn't sound like your problem.
Back firing (firing back into the carburetor) is most often the result of spark plug wires connected to the wrong plugs, or an intake valve not closing.
After firing (into the exhaust system) is he result of raw fuel entering the exhaust system and being ignited. A flooding carburetor or an intermittent or completely absent spark can cause this. So can suddenly closing the throttle, though this is rarely heard with a stock exhaust system.

While I would normally agree with you, I seriously doubt the clean air system is... well... clean and functioning properly. I ended up removing the system, connecting the two Reed valves with hose and put a stopper in the airbox and... Backfire actually did stop. Haven't heard but one since. Ended up checking tires, chain tension, lights, brakes, etc and took it for a 5 minute spin with no tank! Just the tiny aux tank I made hanging off the handle bars! Lol I can't imagine what the dog walkers thought of that sight.

I'll try for a carb sync tomorrow and see if I can't get that #4 to pull it's share of the load. It's still cooler than all the rest. I'll also rinse out the temp has tank and inspect the petcock I cleaned before. Get them ready to mount

TexasKZ wrote: I suppose that is one way to solve the problem. Perhaps the fsm needs an addendum :silly:

Tvag06 wrote: Video of bike backfiring while idling .

Backfire at idle

Oldjeep wrote:

Tvag06 wrote: Video of bike backfiring while idling .

Backfire at idle

What happens if you plug that vacuum port that you have hanging open?