btom750
CB750 New member
So I just bought a cb750. 1st bike, though experience with cars. Its a bobber, custom frame, tank, seat, forks, handlebars, oil tank, ect. Anyway, the guy I bought it from said the engine and carbs were rebuilt. I got it cheaper because it wasnt running, which he said was due to electrical issues. The factory wiring harness is pretty much non existent from the work done to it and pretty much all electrical accessories shaved, so I went and redid all the wiring and now the bike starts on one pump.
Now I went to put gas in the tank and it came out the release valves in the bottom of the carbs. (the guy had drained the tank and carbs of gas). I tightened them up a turn and the gas pretty much stopped except for a few drips, so I connected them in pairs with hose so that they would not leak. When I start the bike its obvious that there are issues with the carbs, I called the guy back (without telling him there were issues) and he assured me that he had rebuilt and rejetted the carbs himself and that they didnt have any issues and that they were good to go.
There are several things: the bike only runs 'strong' with full choke. As soon as I start releasing the choke, the third carb begins making a somewhat loud sucking/whistling noise. Which gets louder and louder as I release the choke until full release the engine's RPMs fall and it shuts off. So one questions is what is this noise?
Also, after running the bike on full choke for a couple minutes the exhaust pipes on cylinders 1,2,3 are pretty hot and would definitely burn you, however the pipe on cylinder 4 is scalding hot, like really really hot (these minutes consist of mostly idling and some revving, also revving seems somewhat hesitant but not that hesitant, I don't really know what to expect since this is my first bike). So there are no air filters on the carbs right now and I tested putting a rag on the mouths for a second while the bike was running. What I noticed is that they all spit out gas on the rag, however when covering carbs 2 and 3 the engine speed did not seem to change, though when I covered the 1st carb the bikes RPMs jumped up really high and when I covered 4th it nearly made the engine stop.
I don't know what to do at this point and I don't want to waste time or money on anything that I dont need to do. Especially since this guy assured me twice that the carbs were good to go. Does anyone know why the bike is having any of these symptoms and what I should do? All help is appreciated.
Now I went to put gas in the tank and it came out the release valves in the bottom of the carbs. (the guy had drained the tank and carbs of gas). I tightened them up a turn and the gas pretty much stopped except for a few drips, so I connected them in pairs with hose so that they would not leak. When I start the bike its obvious that there are issues with the carbs, I called the guy back (without telling him there were issues) and he assured me that he had rebuilt and rejetted the carbs himself and that they didnt have any issues and that they were good to go.
There are several things: the bike only runs 'strong' with full choke. As soon as I start releasing the choke, the third carb begins making a somewhat loud sucking/whistling noise. Which gets louder and louder as I release the choke until full release the engine's RPMs fall and it shuts off. So one questions is what is this noise?
Also, after running the bike on full choke for a couple minutes the exhaust pipes on cylinders 1,2,3 are pretty hot and would definitely burn you, however the pipe on cylinder 4 is scalding hot, like really really hot (these minutes consist of mostly idling and some revving, also revving seems somewhat hesitant but not that hesitant, I don't really know what to expect since this is my first bike). So there are no air filters on the carbs right now and I tested putting a rag on the mouths for a second while the bike was running. What I noticed is that they all spit out gas on the rag, however when covering carbs 2 and 3 the engine speed did not seem to change, though when I covered the 1st carb the bikes RPMs jumped up really high and when I covered 4th it nearly made the engine stop.
I don't know what to do at this point and I don't want to waste time or money on anything that I dont need to do. Especially since this guy assured me twice that the carbs were good to go. Does anyone know why the bike is having any of these symptoms and what I should do? All help is appreciated.