No idle change with air screw adjustment

Is it safe to assume this would be because pilot jets are too large? There is no change whether i turn them out or in.

Engine surges when started cold with choke, but dies before it warms up without it. I have to enrich the idle screw to get it to idle, then lean it back out once she's warmed up. After that everything seems fine except a very rich exhaust smell that follows wherever i go. Still have to do the wet float height check. Any help beforehand would be appreciated.

Thanks.

I took the pilot jets down incrementally from 25 to 17.5 and she now responds to the air screws, but they have to be only a half turn out at max or else unstable idle and lots of popping from the carbs.

And there's still the issue of cold start-ups. Needs choke, which should be normal, yet races to about 5,000 rpm and then dies with it on. Only way to reach stable idle at 1,000 rpm is to slowly turn off choke while enriching idle knob, then slowly lean it back out as she warms.

I'm confused as to whether this is a lean condition, rich, or something else, and caused by what?

Checked for vacuum leaks with starter spray and there are none. The fresh spark plugs I put in are slowly blackening. Clear tube test shows fuel level at about -3mm. Ignition timing at idle looks good. Something I'm forgetting?

I'm not familiar with the VM29 carb. Is it an air screw and not a fuel screw? My bike has the original VM26ss carbs and they have a fuel screw (on bottom engine side of carb) so I might be thinking backwards.

Have you checked to see what voltage you are getting to the coils? Check the link below....I have done this on three bikes now and it made a huge difference in how all three ran.

www.wgcarbs.com//index.php?option=com_co...sk=view&id=Itemid=89

Yes, the VM29s have air screws, not fuel.

I did think about checking the coils after reading that whole "jet needle" thread, and i'll do that as soon as the weather improves. I brought the bike to my buddy's house with a garage so I can work while it rains and of course I forgot to bring my multimeter.

But also while reading that thread and chatting with mrmaxstorey on youtube, I decided it could still be a mixture issue. My logic is as follows; please correct me if I'm wrong:

Even though the spark plugs are turning black and the choke kills the engine, which would indicate a rich condition, I still need larger pilot jets. That way I'll be able to turn out the air screws further, letting in more air to match the greater fuel flow. And hopefully this new proper mixture will eliminate the initial engine surging, as well as the subsequent idle adjustments needed to keep things stable.

Hoping someone else with more knowledge of your carbs will chime in....? But are you sure you have no vacuum leaks? Have you replaced the carb holders?

The symptoms sound to me like the same problems I was having with my bike and a friends 1978 KZ650. We couldnt find vacuum leaks around the holders on his KZ650 but he decided to buy new ones anyways. We put the new ones on and it was like a new bike. All that popping and erratic idle stuff when cold went away. He used to have to let his warm up for 5 minutes before he could ride it. Now its ready to go in less than a minute.

I just replaced the holders on my '77 KZ1000 LTD and I can tell a difference. Mine used to pop like crazy when it was cold but that stopped. I just made a lot of changes on my bike in addition to the holders, but when we changed them on my friends KZ650 thats all we did. We had already cleaned the carbs and made sure the jetting was correct and it didn't fix the problem. (stock airbox/jets on his bike)

If your holders are original I would bet you they are leaking. When new they have a raised ridge that compresses when installed to seal them to the intake. I bet when you take your old ones off they will be flat. The original holders may not be all your problem but I would bet they are at least part of it. If not it wont hurt to change them anyways. Then you wont have to worry about them again for the next 30 yrs or so.

www.z1enterprises.com/ItemDetails.aspx?i...&item=IMK16065-028-K

I read that you checked for carb holder vacuum leaks, but I highly recommend you give it another shot using the instructions in the link below. Notice carb cleaner rather than starter fluid works better when performing the test. Ed

kzrider.com/forum/3-carburetor/586732-kz...-and-sputters#586749

also are you on pod or stock airbox/ exhaust system or straight piped?

im on pods and straight pipe running 122.5 mains and 22.5 pilots most people are usually around the 17.5 area for both.

I changed out the original carb holders soon after I got the bike last summer. I was having some other problems with rough running and stalling after warming up and they may or may not have been part of it. The other thing was a lot of rust in the fuel tank and original petcock. Went through the whole fuel system after that, including a brand new petcock. Also, somehow along the way I had to adjust points and timing. She now runs fine when warm. It's cold starts that are the issue. But I will indeed recheck for leaks using those instructions.

The original set of VM29s were stolen from me one day while I had them off the bike. So I got another nicer set of VM29s, rebuilt by someone with much more experience than I. Only thing was I had never wrote down what size jets were in the stolen set, so I pretty much had to start from scratch. All I remember is the air screws were out 1 3/4 turns, and the mains MAY have been 122.5.

Another thing/update: the first fix I ever attempted on this bike, before I ever had any of the current issues, was try to get rid of an annoying tick coming from the front of the engine. My first reaction was a valve clearance adjustment, but when that didn't help I read it could be an exhaust leak at the header gaskets. After ignoring it until the other day, when I thought it could be contributing to my current issues, I went to tighten all the flange nuts and ended up cracking the flange on the number three pipe. Well, now that same tick is much louder, so I figure it is indeed an exhaust leak.

Not wanting this situation to complicate things further, and considering I was eventually going to put on a fresh 4-1 system anyway, I went ahead and ordered one along with a new mounting kit of course. So now I'm going to wait to do anything further until I have my new exhaust bolted on. I'll be going from an older, beat up Kerker 4-1 + pods, to a new Kerker Meg 4-1 + same pods. Eventual proper jetting should be similar, no? Thoughts and comments in the mean time much appreciated. Thanks to all so far.

For 29mm info at Z1E (scroll down to chart)--
www.z1enterprises.com/Z1CarbGuide.aspx

Good Fortune!

Can I assume that chart refers to VM29s on an otherwise stock KZ1000?

If that's the case I should be going up a step or two on the jets, which would make sense considering what I have in there now.

The air screws on the vm29 smoothbores are different than the air screws on other mikuni vm carbs. On the 29s they have a small hole near the end/tip and due to this hole they work differently than the others do. I would start more like 1/8 to 1/4 turn out from lightly seated and not and 1 3/4 turns out you have yours set at.

gd4now wrote: The air screws on the vm29 smoothbores are different than the air screws on other mikuni vm carbs. On the 29s they have a small hole near the end/tip and due to this hole they work differently than the others do. I would start more like 1/8 to 1/4 turn out from lightly seated and not and 1 3/4 turns out you have yours set at.

I have wondered about that hole before. Any more information on how it affects things?

1 3/4 is where they were set at originally, when the bike ran much better. Now I'm somewhere between a 1/2 and 1 turn out with 22.5 pilots. Any more and lots of popping through carbs and exhaust.

Coil check turned up 9.35v at both. Definitely low. Then I checked between battery terminals and there's only around 11.5v at idle. Enough to start the bike but not spark properly I suppose. So looks like I'm off to get a new battery, then get rid of voltage drops.