1971 CB750 tuneing

[Bhitt_us]

Hi All,
Been a while, I have 71 750 completely restored with all OEM NOS parts. I have had the bike 4-5 years and still have problems with Popping noise in pipes when throttle is closed and slowing down. I have Synced Carbs 100% several times and checked/set all the float height and cleaned & rebuild carbs. Plugs show brown or light black and dry when I pull them. I have adjusted the air screws many times, focusing on leaning mixture if gas is left after throttle shut. I have tried to raise and lower needle clip.

I have been debating trying to change slow jet or move needle some more. It will pop many times when I down shift hard several times slowing for a traffic light. Any ideas, suggestions would be greatly appreciated. Thanks

 

[Loki]

Usually means you have a leak in your exhaust drawing in air.

Loki

 

[dirtdigger]

Exhaust leaks at head? Stock exhaust? if so make sure the crossover tubes at the back of the mufflers are tight. points condensor age/condition? advancer working correct? timing and dwell set correct? Compression good? hard high rpm decels are always going to dump extra fuel in the exhaust. Old style carbs and ignition systems are inefficient its not uncommon to get some pops in the exhaust. Lot of people pay alot of money to make their exhaust pop on decel.... if it isnt bad does it really need fixed? Its not like modern fuel injected bikes that cut fuel on decel with carbs you always load the engine with fuel on decel, especially hard decels.