KZ650/VM22 idle tuning

Hey guys, i'm looking for a bit of advice on idle tuning my kz650. It has the VM22 carbs with a 4-1 exhaust and pods. 3000ft elevation

It runs great after warm but i get carb backfires if i try to rev it past 2000 before it warms up. It also just sounds like a crappy idle. I know this seems like a valve issue, but i checked the tolerances and all the gaps came out to .005in after i shimmed some.

I have an AFR gauge and used that to set my fuel screw and main jet sizes. It's pretty much a solid 0.9 lambda (13.2AFR) through out the whole rev range. No hesitations or backfires

As for the starting procedure: I set choke (enrichment lever) to about 3/4 and it generally starts on the second or third kick (no starter currently). I have to give it some throttle to keep it running. If i shut the choke as soon as I start it, it still runs (with some throttle of course), but runs best at 3/4 choke. Once warm it idles right at 1k RPM with no choke and no throttle. full choke kills the bike at idle and when warm or cold.

Its a 650 motor with a 550 ignition system and advancer. Ignition timing set right on mark.

Carbs were cleaned, synced. 105 main jets and 15 pilots. Fuel level set to the high end of the service spec.

No air leaks found on the boots etc.

timing was set like this after the valve clearances were done: 1 and 2

compression was a bit low at around 115 or so on every cylinder.

Maybe i'm running rich at idle because the choke doesn't cause the engine to rev up on its own? The weird thing is that i had some TK22 carbs on it with some real janky home made carb boots (still sealed good though) and it started like a dream on the second kick and didn't have any issues with a few revs bone cold. Perhaps ill check my AFRs again? Maybe double check my timing chain tension as i got some ticking at idle?

Thanks.

Let me start by saying I don't like the vmxx carbs they are a pain to tune but run good.
First did you do bench sync and insure that all of the slides go all the way up and when at the bottom, or relaxed position, are all slightly open?

Second if you did the above did you then try to sync them with a sync tool for 4 carbs? That maybe the source of your "crappy idle".

At 3000 ft you may be correct on the carbs running a little rich with choke.

Hope you get it sorted out.

Thanks for the reply.

I did sync the 4 carbs with vacuum gauges, but i think the issue was timing related. The bike is a mix of 550/650 parts and apparently the TDC marks on the 550s and 650s are a bit different on the timing advancer so timing wasn't set right. I found one cylinder with 25psi of compression but didn't find anything major in my engine teardown... I'm going through and refreshing the valves and pistons anyways so I think it'll run a lot better after that.

Parts come in tuesday!

Yes 25 lbs is a problem. Your OP said 115 on all. Before tear down a leak down test is in order so you know where the trouble is.
Old hot rod trick when timing marks were suspect or with engine mods was to retard the timing a little. Get the engine at idle and slowly advance timing, while looking at a vacuum gauge, for it's peak vacuum. Then retard timing 1 inch, on the vacuum gauge and lock it down. That usually resulted in a pretty good timed engine,

I did attempt a leak down test but TDC was far enough off that it would just push the piston down when pressurizing the cylinder.... I was quite confused. I did put some oil in the cyl and did another test which came out to 50psi.

Quite the adventure haha.

Oh and they were intially all around 115 a week or so a go. I did a compression test when the header was no longer warming up.