1982 KZ1000J2 - mystery lean - sticking idle

Hi all,

I've been puzzled by this forever. The bike will start OK, but throttle response is terrible and after the bike warms up the idle sticks at around 3K or so. I've tried a bunch of different things to no avail. The one thing that sticks in my head is that when I connected a carb synch meter set (4 vacuum gauges) with a gravity-feed fuel bottle replacing the regular fuel tank, the bike ran great. I think something may have sunk in, 3 years later...

Could a petcock line vacuum leak be at fault? I replaced it shortly after I got the bike, and it is vacuum operated, of course. I guess I'm going to test this by plugging all the vacuum ports (I've already disconnected the emissions stuff) and just hooking up the bottle. If this is the case, will my final fix be a manual petcock that will fit in the tank or do I have to put a valve in-line and leave the tank petcock in PRI?

Thanks!

So when you removed the emissions stuff you plugged the vacuum nipples?
Then the hose to the vacuum petcock should be in good shape and fit tight.
The most common source of vacuum leaks are at the carb holders/ intake manifold boots. I would check there, using a low Idle and some spray brake or carb cleaner. Spray around the boots, where they connect to the head. They are probably bad. New ones can be bought in a set of 4 from most on-line bike shops for many models. I found 4 shipped for about $50.