kz 900 jet size. help please

kz900, 26mm carbs. 4 to 1 v&h street header with insulation taken out. pods. its got 117.5 mains and 17.5 pilot jets in it now. does anybody know what set up i need and also the needle jet setting. thanx in advance.

Stock VM26 from a 76 KZ900 is rich from the factory. I would bump main jet to #120 #20 pilot

what is the elevation where your at also has any major topend work been done to the engine (piston's, cam's ,porting) that sort of thing or is completly bone stock other then the pipe. how does it run now is it running poorly or are you just trying to make it run crisper.

well i live in Indiana. so elevation is probably a little over sea level. Motor work. I put a new head on it. it have a valve job about 600 miles ago. The bike runs great at mid and high range. Now i say great but this is the only bike i have ever ridden. if i hit it hard from a dead stop it bogs down. it also pops on deceleration.

asevans wrote:

well i live in Indiana. so elevation is probably a little over sea level. Motor work. I put a new head on it. it have a valve job about 600 miles ago. The bike runs great at mid and high range. Now i say great but this is the only bike i have ever ridden. if i hit it hard from a dead stop it bogs down. it also pops on deceleration.

The altitude for Indianapolis is about 800 feet above sea level (see www.altimeters.net/cityaltitudes.html ).
Plus it gets real muggy there, I hail from Carmel just outside of Indy (30 years ago, though). So you apparently have the same carbs as on my 1978 kz1000, the vm26ss.

But the other reply was right, according to the carb jets specs I have, your model of the 900 is a richer setup from the factory -- your 900 had the bigger #115 mains and #117.5 pilots (my '78 kz1000 came stock with smaller #105 mains and #115 pilots).

You may in fact need to go to bigger mains/pilots/needle clip adjustment etc. but first, what do the spark plugs look like? Since this is your 1st bike, also important to know what shape the battery's in. Easy to check with a digital or analog meter -- 12v at rest, and 14+ volts when the bike's on and revving to 2000+ rpm.

Pull the 4 spark plugs -- you could have a 'lean' bog off idle, a 'lean bog' meaning that the pilot-to-needle jet transition in the carb's functioning isn't getting enough gas (the needle jet starts coming into action once the throttle is open 1/4 or more).

If the bike idles okay, but bogs right when you open the throttle, it could be a 'lean bog' as above. It's hard to imagine that it's NOT running lean because
- you have the stock jets in the carbs (115 mains and 117.5 pilots)
- you have much-less restrictive pods
- less-restrictive exhaust too.

I'm still trying to get around what Kawasaki did from your kz900 to my kz1000 that allowed the factory to ship my bike with MUCH smaller mains than yours (#105 vs. your #115s) seeing that the carbs are still the same in the bikes (vm26ss). Maybe my bike shipped with a much more restrictive airbox...? I just don't know.

I'd pull your plugs and if they look very dry, and whitish, you may be experiencing a 'lean bog' but check your battery! Just one whitish-looking cell in a wet acid battery means it's time to get a new one. The ignitions on these bikes are sensitive to having a strong battery.

It would be nice to know the following:
- does the bike idle well?
- is it firing on all 4 cylinders (check the head pipes and if you have a cold one you found a problem)
- does it run on all 4 cylinders once you get it going with a more-cranked-open throttle grip? By the sound of it, it sounds like it's only bogging off the line.

I looked at a '79 kz1000 a couple weeks ago that a guy was selling, it was bogging too - low power at low rpms, and I could hear it missing a cylinder. The guy didn't even know it (no harm in that), it felt strong to him (after all, 3 out of 4 cylinders on an 85hp bike is still a lot of power!) The #3 cylinder's head pipe was cold to the touch while the other 3 pipes were untouchable-hot.

Check the plugs too, maybe check the condition of the points, their gap, and the timing, and good luck to you.

OK the plugs look to be fine. they are a white tan color. they look good, it just bogs off the line. as far as the battery. it is good. checked that last summer. it idles just fine too. and all the cylinders are firing. i havent checked the points yet or the volts on the coil. need to do that. possably wg coil mod. i think what ill do is get the 120 and 20 check the points, need to do that anyways, and go from there. Thanx for all your help.

pods and pipe will need a 20 pilot all day long on a bike that is in a good state of tune....no packing in pipe?...120 main easy....i m sure the more knowledgeable will chime in........

it sounds to me like your main jets are pretty close i'd richen up the pilot jet one size and lower (richen up) the clip on the needles by one spot and you should be able to get real close.to perfection.

timebomb33 wrote:

it sounds to me like your main jets are pretty close i'd richen up the pilot jet one size and lower (richen up) the clip on the needles by one spot and you should be able to get real close.to perfection.

forgot the clip position.....like i said the more knowledgeable will chime in and have ....:laugh:
tim knows his sheeeat.....:laugh:

i'm sorry i only human it's been a rough week already and it's only tuesday24 new student i'm in the middle of a nightmare. help!

asevans wrote:

OK the plugs look to be fine. they are a white tan color. they look good, it just bogs off the line. as far as the battery. it is good. checked that last summer. it idles just fine too. and all the cylinders are firing. i havent checked the points yet or the volts on the coil. need to do that. possably wg coil mod. i think what ill do is get the 120 and 20 check the points, need to do that anyways, and go from there. Thanx for all your help.

my bike had the same jets and ran very well except the off stop sighn bog where it would almost quit. Coil mod took that completely away.

timebomb33 wrote:

i'm sorry i only human it's been a rough week already and it's only tuesday24 new student i'm in the middle of a nightmare. help!

no tim,i meant i forgot to mention clips.....you are good......no worries