Won't idle with choke, needs throttle without

Howdy; 750 with BS34s. For the past couple years, my starting sequence has been:

-Start with choke pulled both clicks out
-When idle begins dropping, push choke in one click
-When RPMs hit 1700, push in choke fully, idles at 1000

Following my rebuild (honed bores, new rings, and some lapped valves) the sequence is:

-Start with plunger out two clicks
-When idle drops (which happens quickly) push in both clicks, pulling throttle slightly to maintain ~1000 RPM idle
-After a couple minutes, bike has warmed sufficiently to idle ~1000 off idle
So, my first impression is maybe it's too rich on the idle circuit, but in spring 2021 I set the mixture screws just right (using both plug readings and a colortune) and haven't touched them since.

I'm admittedly not very knowledgeable about the physics of all this, but it seems that refreshing the engine would, if anything, raise compression and require more fuel anyway. 

My second thought is that I may have been overly conservative in my valve shimming, and that could affect it in some way...I'll check them out this weekend and see how they look. They do sound a bit loose, but my other bike's engine is much quieter. 

P.S. - I've got a hiccup at 7,000 during full throttle, but perfect performance otherwise. Maybe that's from the same root issue, I dunno. 

Inputs appreciated. 



 

Do you really need the choke to start it?
My XS1100 has BS34's, and after i got the jetting dialed in, i only need to choke if it's really cold outside.  maybe one click if it's been sitting for a while.

That being said, if you made changes to the engine, you'll likely need to tweak the jets a bit...
luckily the air jet is accessible without pulling the carbs.  i'd probably start there.

on mine, 1&3 have slightly different jetting than  2&4.

Thanks for the suggestion; I tried starting without choke today, no dice, but starts fine with it. It's like 30F in Michigan at the moment. 

However, I did get to the issue - 5/8 valves were too tight, which I didn't expect at all, and one was loose. After shimmying around it's behaving very normally, both warming up and passing 7k. Feeling kinda dumb for this one. 

I'll try starting with less or no choke when the weather warms, couldn't hurt!

When you pull the choke on, it does two things. It will raise the idle slightly by effectively opening the throttle a little. This should happen at even low levels of choke - turn the choke half on and you should see the throttle bar turn as if you are twisting the throttle slighlty.

The second thing it does is restrict air with a second set of butterflies. This makes the mixture richer which is important for starting. If dialed in correctly, this should happen in the second half of the choke's travel.

What this means is that - if dialed in correctly - part choke will only raise your idle a little to prevent stalling once partially warm. Full choke will enrichen the mixture and raise the idle. If you have problem with idling on part choke, but it starts and is responsive enough will full choke, it's usually that idle setting that you need to look at, and don't need to touch the enriching circuit.

I find Kawasaki's to be very cold blooded and always require choke unless previously started, even in the summer time.

Lash closing up after lapping is very common, check the lash again after the first oil change.

Sounds like classic vacuum leak to me. Have you try shooting either carb cleaner or starting fluid at the base of the insulator/rubber manifolds? If carb cleaner, idle drops or engine dies. If starting fluid, idle should pick up. Be careful using starting fluid though. Too much is not good thing. just a squirtshould be fine.