Rpms jump around

Hello to the awsome folks on the KZR forum. I find myself here again in need of some guidance. A few weeks ago I got some excellent help correcting a no spark condition on my recently purchased 81 kz750. The spark issue is resolved and now I find myself embarking into the wonderful world of carbs.
The issue is that my rpms will not remain consistant. The bike will start up without any problem. I have the idle set at around 1800. After a few minutes the idle will drop to about 1k or shoot up to 4k completely randomly. Blipping the throttle usually brings the rpms back to 1800. I recently took the bike for a short first ride down my street, (my first time on a bike) and I'm just keeping it easy in first gear just to feel out the clutch, when the rpms start to run up without any throttle input. I'm new but I'm pretty sure something isn't right.
A little info on my bike, it is a 1981 kz750e 4cyl. It isn't a stock setup. It has the air box removed and the keihin carbs are set for pod filters. Idle jet has been bumped up a size. It currently has a fuel leak at the tee inlet. I have a new one on order but j b weld is helping that out until the part arrives. I also found out while working on my spark issue that my bike has a points style ignition out of a 68. Also the carbs were just cleaned, everything appears to be in good working order except for the rpm problem.

Carb holders at the engine. You mean 78 don't you?
Steve

I bought the bike from a guy in the middle of a cafe racer project. The bike is an '81, but it does have the fuel tank and rear section from a '78 I think. It has a collection of parts to make my life simple.
Will a Crack in the carborators mounting boots cause a problem like the one I'm dealing with? I didn't notice any cracks but I might need to make a closer inspection.

They get hard and crack where they bolt onto the head. You can't see it and it doesn't take much.
Steve

Thanks, I'm going to take a closer look.
I forgot to mention that all of the vacuum lines are removed and the ports are plugged, the breathers on the forward valve cover have the hoses removed with small air filters installed. I don't know if that makes any difference. The fuel tank has just a simple on/off petcock with gravity feed to the carbs. No vacuum operation.

Those aren't breathers. Connect the two with a hose for now.
Steve

What does that do? I suspect it was part of some emissions or something.

With all the other hoses, they inject air into the exhaust ports. If you don't have the air box or the plumbing, they need to be blocked off.
Steve

VegasRob wrote: What does that do? I suspect it was part of some emissions or something.

Yeah it was routed back into the airbox through a vacuum operated valve.

Take some ether or braklean and spray around the carb/boot area while the bike is idling. You'll def hear the rpms rise if there's a leak. That's how I found that my throttle shafts seal was still leaking even after I replaced that he boots !

Okay, I'll round up some hose and link them together. Should I be on the hunt for the stock stuff or is plugging them sufficient. What kind of trouble can this cause?

I'd go with the air box. The rest can stay off. Pics?
Steve

Here's some pics