I would appreciate some help with a problem I am having. I have a 78 750 F I replaced the engine with a 78 750 K with very low mileage. I had to use the carbs from the F. I rebuilt the carbs. The problem is that the bike won't idle or run without the choke on full or almost full on. It starts right away (with the choke on) runs great at 3,000 rpm (with out the choke). The bike is completely tuned. When I rebuilt the carbs I dipped them blew them out with compressed air as well as carb cleaner. I replaced all the gaskets and jets needle valves in short everything that could be replaced short of the slides were replaced. I even pulled the low speed jets (pressed in) and cleaned them and used some fine copper wire to make sure they were clear. and I blew out the passages with carb cleaner. I am sure the floats are set perfect. The vent is open. The adjustment screws are set to spec. It makes a very SMALL difference if I open them about three turns instead of 1-3/4 but not enough to matter. I have pulled off the carbs and rechecked everything I can think of so many times I dream of the damn things. When I rebuilt the carbs I replaced the needles they don't have the five grooves but neither did the old ones.
Since I bought the bike new I know those are the originals. On another site someone who had a similar problem solved it by cutting the grooves in the needles and repositioning the needle which solved the problem. I don't mind doing that but logically it seems like if the stock needles weren't grooved why should the new ones need the grooves. Also it seems to run good at high speed (3,000 rpms and over) without the choke. So logically it seems it has to be a problem with the slow jet circuit, although logic doesn't always apply. The carbs are Keihin (42a ? QA ?) the main jet is 105 and the slow jet is 35. Another fact is that I live at about 7,000' altitude and generally operate the bike at between 5,000 and 7,000'. I don't think this problem doesn't have anything to do with the altitude since the bike has run fine at this altitude for several years but I just thought I would mention that. All I want to do is get the bike on the road before the snow flies which is pretty early up here in the mountains. I know there has to be something simple I am overlooking. Any help or suggestions would be greatly appreciated.
Bob
bobstanley@juno.com.
PS. If I cant fix this problem is there another carb setup that I could use That won't bankrupt me?
