won't rev off idle

the bike is warm when this is happening. I've looked at the plugs id say there on the rich side

Try dropping the needle a spot or two and see what it does.

34mm mechanical slide carbs seem way too big IMO, CV carbs flow less so their size doesnt translate directly over. Look at the kz900/1000 for example they ran 28/26mm mechanical slide and went to the 34mm CV carbs later on. I would think you should be around 26mm fr a mechanical carb

ill try that tomorrow. weren't the factory keihinsa 32 mm mechanical maybe 34

Factory carbs are CV (constant velocity) and work off of vacuum, kind of a displacement on demand type of thing, like the rochester quadrajet. They may say they're 34mm but flow more like a 26 or so mm mechanical slide carb

It sounds like he went with the VM32 kit that's supposedly pre-jetted and pre"needled" for CB450, CB500, etc. Sudco and others also make a VM30 kit that's jetted and needled specifically for the KZ400, but from reading posts from people who bought that VM30 kit, it runs lean out of the box, more so if the exhaust is opened up and pod filters are installed. Since he went with the 32s, it sounds like a really bad bog off idle due to being overly rich.

Like someone else suggested, try lowering the needle one clip (ie raise the clip position one notch) and drop a size on both pilot and main and see what it does and go from there.

If it gets better, but the bog is still there, find out what needle is in it and buy the next 2 or 3 thicker and less tapered needles and try each one til you find what works. That's the great thing about the Mikunis; Huge selection of needles and jets.

We just finished tuning our neighbor's '75 CB500T that we cafe'd for him. We strongly suggested upgrading to Miks, but budget wouldn't allow it, so he stuck with the stock CVs . The only performance upgrades he wanted were pod filters and a more open flowing exhaust. Stock jets for that carb/bike are 38 pilot, 38 slow and 145 main. Before even firing the bike, we upped the main to 150 and were surprised it was still quite lean on top, I mean stumbling lean, but not "white plugs" lean, but it idled well, if just a tad lean. We went to 155 mains, which cured the top end lean condition, but made it rich at idle (gotta love the CV carbs where the pilot gets its fuel from the main... Ugh!) So after jetting the pilots and slow jets down to 35, the bike is perfect. I know that has no bearing on this thread, but shows you how funky jetting can be. It'll be easier since the OP here has the Mikunis.

well thats good to know hmm. And correct i bought pre jetted and needed kit carb pod filters throttle cable... sounds good ill mess with the needle and pick up some jets for it. would the jetting be effecting the cylinder that isn't running that bad? since they are both jetted the same and the left cylinder is running pretty good and the right is barley firing

If one is running fine and the other isn't, since you have brand new carbs I'd look elsewhere, spark (plug/wire) or compression most likely, could be valve clearances etc

I would start by checking your valves/ doing a compression check on both cylinders to see if they are the same. They carbs may need to be adjusted separately ( slightly) to compensate for differences in the vacume between cylinders. Without any major jetting ( maybe just moving a needle clip) or mods at this point it should be running close to what you want from what it sounds like. I know on my 440 the right cylinder has lower vacume pressure and causes it to run a little funny.

sounds good ill look into the valve train on it first and try and source a compression gauge. the plugs coil and wire are new do i know its not that. thanks for all the info hopefully i van get this running and on the road soon.

Switch the plugs and see if the other cylinder becomes the problem. Otherwise checking valve clearance is really easy. Compression guage you can barrow from an auto store in most places.

ok so i checked the valves and the exhaust valve was out so i have it at .004". So with the choke on the bike has been running great and the bad cylinder has been coming back and is running better. When the choke is off it might as well be a single cylinder. I'm pulling the carbs off and making sure the jets are the same besides that I'm not to sure which direction to go in.

I'm inclined to think vacume leak or that the piolet circuit is not giving enough fuel.