Selecting the right pilot jets

Hey Tb33 it's thadley55 u helped me out with a manual for my kz900 last year, thanks it helped alot. U mentioned earlier in the thread that u use a numbered bit to drill out ur pilot jets, is that an easy task or do I need a machine shop set up to do it? BTW if pilots are too small will the motor be sluggish untill she revs a little?
ThanxB)

thadley55, what kind of carbs do you have? I would recommend buying new jets if they are readily available. I've heard that drilling them yourself can cause problems, but some say it's fine, while others say its not. It cost me $16 for four jets shipped to me, which isn't super cheap but its still a good price.

According to a manual I found for my carbs, there are a few things to try to see if your pilots are too small. It says to turn the grip a little under no load and see if the engine revs smoothly, if not, the pilots are too small. It also says if you cannot maintain a steady speed between 12-25 MPH that your pilots are too small. I assumed mine were too small because it will not start cold without the choke fully applied, revs very rough until it is warmed up, and if I try to maintain a speed of 25 mph, I will have a little bit of misfire. You might also want to try adjusting your air screws to see if that could help you out.

thadley55 glad i could be some help, i usally have have a dozen sets of carbs laying around at any given time so if i need to make a jet change like that i'll just make my ownby drilling out the originals to the size i need but in your case i would probably buy the same ones that toadson bought they are cheap and if you ever decide to got back to origanal you will still have the stock pilots to put back in.the main reason i do alot of this stuff my self is out of necessity it can be a real bitch trying to find replacement parts up here in a timely fashion or at all. so sometimes i have to make what i have at hand work the tool i use is called a pin vise they are operated by hand and they have a collet that holds the small size number drills and just take your time and go easy with it taking care not to put side loads on the bits because they are very thin and fragile the last thing you need is to break one of in the jet instant throw away.

Thanks Guys, I'm not sure which carbs I have. My bike is a "B" motor with an "A" frame and I think,according to a carb link I got off here last year,I have '75 Z1 carbs which I think are 28mm it was either '75 had 28 and they went to 26mm in '76 or the other way round I don't know if u guys know what link I'm talking about maybe you could post it. Anyway I checked my jet size and I have #20 pilot and 120 mains. I am running pods and V&H 4-into-1 headers. It is sluggish up to 4 g's and then takes off. I just ordered a vacum guage set so I can synch the carbs, so we"ll see. BTW she still needs rings but Maybe I can get the carbs good enough so I can toodle around town untill I can save the cash for a minor rebuild. Thanks so much for the help. "The spirit is willing but the knowledge is weak"
ThanxB)
P.S. This is a 76 kz900

check and clean your mechanical timing advancer might help..

Come to think of it I did clean it and then I lubed it with some dielectric grease that's when I started having trouble. I thought I fixed it when I cleaned it again. Is there any other lube u could recommend?

it should be good then,
check carbs and filters for debris then
i'd buy some more jets im going to order some of each size and a colour tune like OMR
should be easy to dial it in,
this is what i intend to do.

thadley i like to use moly grease it seems to work the best for me anyway i wont cake and dry out like so types of wheel bearing grease will and it doesn't seem to atract dirt as easily either dielectric grease is used for packing electrical connectors it really isn't a grease at all clean it out and start with some moly.

I got my new jets in today, but in the process I developed a migraine. I got the bike running, but haven't messed with the air jets or rode it yet. I had it idling off the choke pretty quickly, but I could tell it still needed some time to run to get all the air out of the carbs and accelerator pump. It always seems to pop a lot when running right after I've removed and replaced the carbs. If the weather is nice tomorrow, I plan to take it for a ride after school.

I got my first test run in today. My #1 cylinder kept backfiring through the carb the entire time I was cruising, but after riding it I checked the air screw. I only had it out 1 full turn, while the others were 1 1/2 turns out. I adjusted it to 1 1/2 turns, so I'll have to see if that fixes the backfiring. If not, something may have found its way into a jet while I had the bowls off. I think it will run a lot better if I can get that one cylinder straightened out. Even idling, you could tell it wasn't hitting on one cylinder, and the idle would fluctuate.

toadson wrote:

I got my first test run in today. My #1 cylinder kept backfiring through the carb the entire time I was cruising, but after riding it I checked the air screw. I only had it out 1 full turn, while the others were 1 1/2 turns out. I adjusted it to 1 1/2 turns, so I'll have to see if that fixes the backfiring. If not, something may have found its way into a jet while I had the bowls off. I think it will run a lot better if I can get that one cylinder straightened out. Even idling, you could tell it wasn't hitting on one cylinder, and the idle would fluctuate.

If not already done, would check/adjust valve clearances (especially #1 intake), and assure correct ignition timing and proper operation of advancer with strobe-type timing light by watching it move back and forth as rpm is varied by blipping the throttle.

Am doubtful that the above mentioned pilot air screw adjustment will resolve the backfiring, because turning the screw out leans the pilot mixture by allowing more air into the mix. But do concur with having them equally set initially prior to further fine tuning of the idle rpm.

Good Luck!

I never have checked the valve clearances on this bike, I think mainly due to the fact that you have to have a set of shims to change the clearances. I installed a new set of points and condensers last year and set the timing dead on, but I'm thinking about checking it again to make sure it is still set right.

I never had problems with the carbs backfiring until I installed the #20 pilots. It doesn't really make any sense since I am giving the carbs more gas. I might have to take them off again and make sure there is no junk caught in the needle seat or anywhere else.

If all else fails, I may check the valve clearances. This bike has over 30k miles so I'm sure its due for that.