KZ400 throttle issues

Just remembered something that happened to me with my 440 about 5 years ago and it sounds very similar to your original description: Running good from cold with choke on then by time it's warmed up & off choke it began to lag. Cruising down the road it felt like i had tossed the anchor out.
Ultimately i found the carb mounts had started to flex & a miniscule gap developed between the carb mounts (both of them in my case) & the cylinder head.
I solved this by cutting some sheet gasket. Put carb holder on page of gasket, traced the inner & outer perimeters & used a razor to cut them out. Installed them between mounts & head. Solved the problem.

Flipping a two year old filter seems like a bad idea. You are lible to end up with two years worth of spooge in your carbs. New ones are cheap.

Might not solve it but you never know. The filter will clog much faster in that direction though. If that filters old make sure you don't just flip it around and use it again. Then all that stuff from the filter will end up in your carb.
Edit: looks like TexasKZ edged me out for first :laugh:

One possibility might be insufficient valve clearances whereby minimal clearance could allow a cold engine to crank and run for a few moments until it warms enough for the clearance to disappear.

Could also inspect functioning of the advancer unit to assure it's clean and lubed and not hanging or sticking for whatever reason.

Good Fortune!

I think I'm going to try the new filter + refitting the boots first, if that doesn't work, I'll head to the valves and check the clearance.
Although the bike starts better after it's warm, the idle is just as rough and it still bogs down around 3.5k RPMs
I'll have an update either later today or later next week. Thanks!

Well, cleaned the carbs, adjusted the fuel filter and decided to keep it because the one I bought broke on installation. Put everything back together, now the bike won't turn over. I think I'm a little beyond my scope here and I'll probably just take it to a mechanic. I appreciate everyone's help.

I checked around and there doesn't seem to be a mechanic within several hours drive who will work on the bike, guess I'm figuring this out myself...any thoughts?

I've charged the battery and checked it with a volt meter, it's putting out , putting my hand over the intake I can tell I'm getting good compression, although when my hand was over the intake I got gas all over it. Is this normal?

I also checked the spark plugs, I'm getting good spark, it just won't catch. Sometime it sounds like it wants to start but just won't.

That's the downside to these bikes. Your pretty much stuck fixing it yourself. After a point you learn to find enjoyment in the struggle :evil: Have you tried seeing if it will turn over with starting fluid?

Yeah, sprayed starter fluid in a carb before trying to start. It did not turn over, but cam3 close a few times

Have you checked the valves?

Not yet, I need to get some shims to check. I'll be on vacation this week's so I'll update when I get back. Thanks for the help!

Does it bog with increasing throttle or increasing rpm?