No pilot screws on KZ650?

ok so i pretty much sorted out my stuff in the electrical department, at least as much as i can without the bike actually running.

but now i can't get it to start. i rebuilt the carbs and as far as i can tell all my passages are clear. i'm going to go and double check the pilot and choke passages since that seems to be an issue according to other threads.

one thing that concerns me though is my carbs have no pilot screws. i was reading through the shop manual and it mentioned them in the adjustments. when i thought about it i didn't remember removing any screws from there. but my carbs have no provision for them.

it's not like they're missing. there are no threads and the hole is blind, it doesn't go anywhere.

are mine maybe just an early model that just doesn't have an adjustment for the pilot circuit?

i also have no vacuum petcock, just an on/off/reserve type, so i know mine is rather early.

hopefully i can figure it out on my own but i was wondering if anyone here has heard of this before.

It depends upon which set of carbs your 650 has. Some have just the pilot or fuel screw on the bottom of the carb. Some have just an air screw on the side of the carb, and some have both a pilot /fuel and air screw.

Further on some of the later models with just the air screws (on side of carb) there is a plug over them that has to be removed to get at the screw.

You don't say which model KZ650 you have; it does make a difference. My 1977 C1 has air screws on the sides and no pilot screws. Also, both 1977 models (B1 and C1) did not have the vacuum petcocks. Be happy your bike doesn't have the pilots or vacuum petcock - it makes life simpler. Ed

sorry, it's a 76. on the vin tag it says july of 76 and the vin says kz650B.

it's about as early a model as you can get.

i did manage to get it started. it lights up as soon as you hit the button and idles, but i think only two cylinders are firing.

as soon as you hit the throttle it pops and shuts off, and only the left two cylinders are hot. i know both the 3 and 4 cylinders have spark, so i'm guessing there's a blockage keeping fuel from the engine?

the overflow tubes on the bowls are also dripping slightly. the needles are not sticking though. i'm thinking something is just stopped up. the air adjustment screws wouldn't affect that right? they're out 1.5 turns. that's usually about right on most carbs but these don't seem to be most carbs haha

It may have been build in late 1976, but it is a 1977 model (there is no 1976 model KZ650). July is pretty early so it must have a very low VIN.

I doubt seriously that there is any blockage preventing 3 & 4 from firing; that is almost impossible. Air adjustment screws cannot cause a blockage, they simply control air - not fuel. Are your spark plugs wet or dry?

Regarding the overflow dripping -
Are your overflow tubes are dripping when the petcock is in the "OFF" position? If so, you have 2 problems and both need to be corrected. One is that the petcock is leaking internally allowing fuel to pass through it when it is turned OFF, and the other problem is a carb problem (described below). If the petcock is leaking internally you will need to disassemble it and carefully clean the internals with a non-abrasive cleaner (like carb cleaner). The petcock can get a little funky inside but usually cleaning the manual type like you have is enough to correct the problem. After cleaning you can test it to see if the leak stopped.


If the overflow tubes are dripping (even when the manual petcock is turned "ON") there are only 3 possibilities:

1. The float valves are a little dirty or sticking. Keep in mind it only takes a spec of crud from the fuel tank to keep the valves from closing tightly and this will make them drip. You can easily clean these by simply dropping the bowls with the carbs still on the bike and cleaning the float orifice and needle with a not abrasive cleaner like carb cleaner and a Q-tip. I also recommend a quality fuel filter.

2. The brass overflow tube in the carb bowl is cracked. This is unlikely but possible and easy to test. Drop the fuel bowl, sit the bowl level, fill bowl up to overflow with fuel (outside-no smoking) or alcohol, see if fuel leaks out. If not, brass tubes are fine. Otherwise - repair.

3. The fuel level is set too high; another easy thing to test. With the carbs fully assembled and still on the bike use the clear tube method to check the fuel level. Just do a search on this site for the test instructions - they're easy to follow. If the fuel level is too high you will need to adjust it.

number 4 plug is dry. it's also a new plug.

i just feel like something is keeping fuel from getting to the cylinder.

it will start and run somewhat, but you can't give it any throttle at all. almost like the ignition advance isn't working.

it doesn't seem like it's running on all four to me though.

maybe i missed a passage in the carbs when i cleaned them?

and the petcock is ok. it turns on and off and doesn't leak.

is it possible it's just plain not getting enough fuel to the carbs? like even though the bowls fill up they aren't getting enough to actually keep the bike running under a load? the flow does seem a little weak to me even though i've cleaned the screen as best i can. i just don't want to remove it yet because there is some junk in the tank. this is like the super early stages of getting the bike running, so an in line filter and all that will come once it's in running, riding shape.

JoeC650 wrote: number 4 plug is dry. it's also a new plug.
i just feel like something is keeping fuel from getting to the cylinder.
it will start and run somewhat, but you can't give it any throttle at all...
maybe i missed a passage in the carbs when i cleaned them?...
is it possible it's just plain not getting enough fuel to the carbs? like even though the bowls fill up they aren't getting enough to actually keep the bike running under a load?...

If fuel isn't being sucked into the combustion chamber, one possible reason might be an obstruction in the carb pilot circuit.

Here's a pretty good pilot circuit cleaning method that's usually successful:



Wear eye protection while spraying carb cleaner, because the spray always backfires.

For more gory details, click here > www.kzrider.com/forum/3-carburetor/48928...pilot-circuit#489287

Good Fortune!

Are the carbs hooked up to the stock airbox? Ed

no the airbox is off. i've just been pulling the carbs on and of so much i haven't bothered putting it on.

i know it will run lean without it because the jetting is meant to have it on there but i also figured that the bike would at least run and rev without it.

i'm going to try pulling them back off and doing what patton said.

i did spray good through all the visible holes but honestly i did not see whether or not it made it out of the actual orifice inside the bore.

would not having the airbox on really be enough to keep the bike from running at all like that?

It will run like crap without the airbox, so troubleshooting other engine problems becomes nearly impossible. Ed