HUGE carb problem BAD STARTS

Hi just got done cleaning my carburetor on my 1973 z1 by an ultrasonic cleaner, I took it compleately apart, it has new orings, gaskets, all jets were checked or rplaced. But when I start the bike;;; it has no big problems starting right away and goes into hi-rpms on chocke but it smokes like crazy, but than as it starts to get a little warm the chocke does not keep the bike at high rpms anymore and it dies with the chocke on all the way or part way, suddenly the chocke has no effect on the bike. So I restart the bike again and the chocke does nothing anymore for the bike, I have to try to hold the throttle but if I give it too much it will die and if I give it too little it will die. So I have to keep restarting or I have to hold the throttle just right so it does not die, And during this whole process the bike keeps smoking like crazy even with the chocke off. Finally after about 2-3minutes of trying to warm up the bike it finally sets into regular idle and than the bike runs like a dream and it does not smoke at all, I have had this problem for the last week everytime I start the bike from a cold start. DOES ANYONE KNOW WHAT COULD BE THE PROBLEM. I hate that it starts up so bad and I know there got to be something wrong with the chocke. any help would be great.

My '75 actually has the same behavior, and always has, except the choke losing effect doesn't happen to me. I generally start it at half-full choke, and get some smoke while it warms up. After about a minute, the smoking will stop, and then it will remain at 3-4k RPM until I drop the choke completely. Not sure on why the choke would have no effect, unless maybe the idle jet or needle is like completely open or something? Then that might explain why there would be no effect with the choke. I'm no expert to carbs myself though, so I could certainly be wrong. :blink:

take the tops off of the carbs and raise the needles a couple threads. worked for me when i decided to run straight pipes and had the same problem. also check the high idle screw.

This out-of-control behaviour is often reported as due to poorly seated or leaky Carb Holders, Carb Holder Vacuum Caps or difficult to tighten Carb Holder Bolts.



Be prepared to:

-1) Re-seat or replace Carb Holders,
-2) Re-seat or replace Carb Holder Vacuum Caps,
-3) Tighten or replace Carb Holder Bolts with new Allen/Hex Head bolts.

Best of success.
Bill

toolman5774 wrote:

My '75 actually has the same behavior, and always has, except the choke losing effect doesn't happen to me. I generally start it at half-full choke, and get some smoke while it warms up. After about a minute, the smoking will stop, and then it will remain at 3-4k RPM until I drop the choke completely. Not sure on why the choke would have no effect, unless maybe the idle jet or needle is like completely open or something? Then that might explain why there would be no effect with the choke. I'm no expert to carbs myself though, so I could certainly be wrong. :blink:

Might be leaving the choke applied too long which could be fuel-fouling the plugs.

Temporary exhaust smoke after cold start likely results from old hard worn valve stem seals. Usually a harmless condition which could be addressed next time the engine head is removed for some other reason.

Good Luck!

So I guess that I don't have an internal carb problem. I will have to start by checking the vacume leaks, but wouldn't a vacumme leak also cause regular driving problems?? the bike runs fine when warmed up. I will also check the top carb seals but those are new, is there any other seals that could be wrong? or could I have some idle or chocke jets/passages pluged??? Let me know. thanks