Selecting the right pilot jets

Early last year I rebuilt my carbs (VM26's) for my 79 KZ1000 LTD. I believe the kit I used included #15.0 pilot jets, and 102.5 mains. The bike acted like it ran lean, so I ordered #110 mains for it, and it didn't seem to solve the problem. After riding the bike for so long and doing some research, I've come to the conclusion that my pilot jets are too small. I am going to double check that the pilots I have are #15.0 before I order any more.

I've recently read a post on here talking about MAC headers and having to rejet. My bike has a 4 into 1 MAC header and stock airbox. The member said when he installed his MAC header, he had to install larger pilot jets. Once I read this, I started looking into the symptoms of having too small of pilot jets. On a cold start, my bike will not run without the choke being fully applied. Even on a warm day, it still needs the choke. It also does not rev smooth with a small blip of the throttle, or while gradually increasing the gas. It just sounds lean until it has fully warmed up. Once warmed up, the bike runs great. I've also cleaned these carbs multiple times and I know they are clean, so this should not be the problem.

So assuming my pilots are the problem, what would be the next best size to try? On z1enterprises, they only list #15, #20, and #22. Would #20 be too big of a jump? I've always heard of people using #17.5, but I'm not sure why Z1 doesn't list it.

i ue 20 pilots in all my stock carbs i bought a couple of sets over the years but the rest i have a set of small number drills and just drilled them out to the same size as 20's. i have my fuel screws set at about a turn out on most of them so it is right in the ball park.

Awesome, thanks! I wonder why they even include #15 in the rebuild kits? My carbs have an accelerator pump on them, so I guess that maybe #15s would be alright on a completely stock bike with the accelerator pump. Hard to believe a header can throw it off that much.

more air out more air in the whole theroy of an air pump and thats all these engines are is an air pump so if you make the exhaust more efficent then you have to add more fuel to keep it from going lean, right.

toadson wrote:

...79 KZ1000 LTD...#15.0 pilot jets...ran lean...pilot jets are too small...cold start, my bike will not run without the choke being fully applied. Even on a warm day, it still needs the choke. It also does not rev smooth with a small blip of the throttle, or while gradually increasing the gas. It just sounds lean until it has fully warmed up. Once warmed up, the bike runs great....

Am thinking oem default pilot air screw position is 1.25 turns out from lightly seated.

Likely already done in this case, but if not, could enrichen pilot circuit mixture by turning IN the pilot screw 1/4 turn and test run for effect. As known, turning IN restricts volume of air reaching the pilot jet, which allows less air past the pointed tip of the screw needle.

Good Luck!

I have the same problem with my kz 700a1. I want to know the pilot adj for my bike from experience on working on similar jap bike I was thinking about 1.5 turns out and go from there.

1 1/4 to 1 1/2 turns is pretty standard for most carbs it is a good starting point at least.

I checked my pilots today and they are #15's. I've got some #20's on the way so I'll let you know how it runs after I install them. Thanks for the help!

You will not believe the diffrence. Roy

I have diddled with VM26 more than I care to admit (and they are still semi-baffling)...I have two sets and have rebuilt them both. These are both off KZ1000A1's and presumably identical. On one set, when the air pilot jet is fully seated, the very tip of air pilot screw ever so slightly protrudes into the throat of the exhaust side...equally in all four carbs. On the other set of carbs, when fully seated, the tip of the air pilot screw does not protrude into the carb throat. I have replaced the o-rings on all these air pilot screws and the springs also. So, in seemingly identical carbs from similar bikes, backing off a set number of turns will yield different results...anyone else notice this?

Wow Z1 Enterprises is fast on shipping. I ordered the jets late Friday night, and they have made their way from New York to Illinois already, I'm impressed! I won't be able to install them until Wednesday at the earliest, but here's to hoping it fixes my problem.

McDroid, my air pilots were set about two full turns out, but I'll have to check and see if mine will protrude into the carb throat like you mentioned. I know how it is to mess with these carbs all the time. I bet I've removed and worked on them 15-20 times since I bought the bike almost two years ago.

so there real easy to takeoff now then, i usally go thru this for the first little while if i'm usig a new to me anyway set of carbs or a new style of them i'm doing that right now with my lectrons and also with a set of 33 smoothies i just put on my little bike .