kz750 idle adjustment

Hi i have a 79 kz750 twin and i am having trouble getting the idle just right my set up is the bs-38 carbs with a 140# main jet and a 50# pilot jet. I have cleaned the carbs and vacuum synced the two. My exhuast is straight pipes with 3 inch baffles and i am running pod filters. The problem i am having is when i get the bike warm and go to turn off the choke it starts to sputter around 1500 rpm and want to die. I have also set timing perfectly and and the bike will start within first few kicks( i dont weigh a lot so it takes me a few tries). The bike also has good and even compression across both cylinders and brand new plugs gapped correctly along with new fuel lines and filters. the tank is clean with no rust and the pet cock has also been cleaned however is hard to open sometimes.

My questions are whats the proper idle rpm and what can i do to adjust the idle higher so i dont have such a rough running bike?

I appreciate any help i can get as i am really getting flustered.


Thank you in advance!

Correct idle for 1979 750 twin is 1000 RPM, which mine does clicking like a swiss watch. Not sure what is wrong with yours, I would start by adding a stock airbox and some mufflers. What you describe sounds like running lean but it could be either a vacuum leak or the straight pipe and pods.

It is running lean popping at idle and the common lean condition symptoms i have read my manual and i see 1050rpm is common idle and i see the pilot screw and idle screw. I am wondering if i adjust the screw will this get me richer or how do i fix this or to be running richer what would i do?

The screws on the sides of the carbs are fuel screws for idle adjust. Backing them out riches up the pilot feed for idle. Start with about 2T out from all the way in.

Before trying to tune jets and needles (if not already done):

1) Clean fuel tank, petcock and install inline filters

2) Clean carbs and all passages, especially if you are having pilot problems.

3) Set fuel levels in bowls with clear tube before adjusting anything else.

4) Check for vacuum leaks at manifolds (carb holders) they are notorious for leaking.

5) Check timing/mechanical advancer with rising RPM. These will make all kinds of tuning problems.

I have done everything. that you mentioned above and how would i check for manifold leaks? are you talking about the boots that secure carbs to block. if so they are in great condition no leaks. i believe it just needs idle adjusted as it runs good above idle pops a little on decel but not much. mostly just idle where it pops and wants to sputter and die with choke no on.