bike is poppin

[olmoggy]

first time to post hope im doin it right. i have a 76 honda cb750. starts first kick idles fine,fast as hell but when its warmed up and i slow down or stop i get a popping noise sometimes its a low rumble popping some times it really pops loud. adjusted valves,timing is dead on already cleaned carbs and gaped and installed new plugs.still pops but only when good and warm. one thing i find strange is that the #4 cylinder runs 100 degrees cooler than the rest. i found this out by holding a handheld gauge at the same distance from all 4 of my pipes. i am really lost here any help would be great

[Johnj]

I'd say the cool cylinder is running richer that the other three. Lean mixtures will pop when deaccelerating. Make sure all four carbs have the same main jets, and intermediate jets with the needles set the same.

[olmoggy]

thanks. but the weird thing is that #4 which is runng cool, the plug actually looks like that cylinder has a perfect mixture the other 3 cylinder that are running 100 degrees hotter the plugs are black with soot even with new plugs and riding it about 5 miles. any other suggestions? forgot to mention all main jets are tha same all slow jets are the same and the clip position on the nedles are all the same

[mydlyfkryzis]

Could be a vacuum leak.

[olmoggy]

thanks. thats where im headed next,vaccume leaks and exhaust leaks

[honda750]

also check the coil wire to cylinder 4, it might be getting weak spark and only firing occasionally.
_________________
recipes forums

[olmoggy]

ill try and swap wires around. thanks for the info.