knightcrawler
1979 CB750K DOHC
Hey guys,
I'm new to the forum, hoping to get some help here and be able to help out a bit myself.
I bought a '79 CB750K last year for $300 with 12,000 original miles. Engine was off the bike and most of it was in pieces. I managed to get everything put together and cleaned the carbs. I got it running(not well) and it seemed like it needed air cut off valves. I bought a full kit and completely rebuilt the carbs, took them apart, soaked them, replaced needles, jets, adjusted floats to spec, replaced air cut off valves etc. I put the carbs on tonight and it still is running rough. It sometimes has a loud knock at low idle but after 2,000 rpm it smooths out. Sometimes I can hit the throttle and it comes up fine, other times it dies. Very inconsistent. I checked the ignition timing and it was right where it should be. Coils are good, need to double check the spark plugs.
Here is one thing that might be very helpful in figuring out the problem, when I hook up my carb sychronizer, all of the cylinders are in the red where it says (Late valve timing or leak at intake etc.). Last year before I rebuilt the carbs I checked and it wasn't leaking, but I still need to check this time just to be sure.
Any advice/ideas are appreciated.
Stock air box and a 4 into 1 exhaust.
Side note: anyone else in the Grand Rapids, MI area?
I'm new to the forum, hoping to get some help here and be able to help out a bit myself.
I bought a '79 CB750K last year for $300 with 12,000 original miles. Engine was off the bike and most of it was in pieces. I managed to get everything put together and cleaned the carbs. I got it running(not well) and it seemed like it needed air cut off valves. I bought a full kit and completely rebuilt the carbs, took them apart, soaked them, replaced needles, jets, adjusted floats to spec, replaced air cut off valves etc. I put the carbs on tonight and it still is running rough. It sometimes has a loud knock at low idle but after 2,000 rpm it smooths out. Sometimes I can hit the throttle and it comes up fine, other times it dies. Very inconsistent. I checked the ignition timing and it was right where it should be. Coils are good, need to double check the spark plugs.
Here is one thing that might be very helpful in figuring out the problem, when I hook up my carb sychronizer, all of the cylinders are in the red where it says (Late valve timing or leak at intake etc.). Last year before I rebuilt the carbs I checked and it wasn't leaking, but I still need to check this time just to be sure.
Any advice/ideas are appreciated.
Stock air box and a 4 into 1 exhaust.
Side note: anyone else in the Grand Rapids, MI area?