Won't stay running

formz said:

1980 CX500



Rebuilt the carbs, although they were immaculate when I pulled them apart so they didn't need much cleaning. The bike starts right up but it just will not stay running without the choke pulled. It responds to throttle input just fine and if I give it a little bit of gas it will stay running without the choke.



Some other things that may help: one cylinder seems to be running a lot hotter than the other judging by exhaust temp. I'm also getting slight backfires/sputters out of the exhaust. I know the gas is clean and I have a fuel filter on it.



Any ideas? I tried adjusting the idle with the screw but it doesn't seem to do anything. I'm stumped!

Click to expand...

hi formz,and a warm welcome from spain.first things first.put your bikes details and your location into your signiture line.



if you are happy your carbs are lean....sweet

because you need choke,it sounds as though you have dirty carbs.but,

...your last line says something else.idle screw is the only big black knob,yes?located between and under the carbs

winding it in or out does nothing,is that what you are saying?

Did you separate the carbies when you rebuilt them? If so, they MUST be syncronized so that they work together as one. This COULD be A reason one side is running hotter than the other, and a very GOOD reason why the bike won't idle.



To start working on the idle mixture screws, turn them inwards to "lightly" seat them, and then turn out 2 1/2 turns. This SHOULD keep the motor running so that you'll be able to "fine" tune each carb. IF those aluminum caps ON the idle mixture screws have like a "wing" on 'em? These should be cut off to help fascillatate your fine tuning, as they were added onto these bikes sold in America per E.P.A. guidelines (at the time) and are no longer needed.......not to mention making it QUITE a Pain in the backside when adjusting...lol.....For as you have probably already noticed, there are 2 "restricting" lips one either side of the idle mixture screw on the bottom of each float bowl, that was SUPPOSED to limit how FAR you could adjust each screw. But, without that corresponding "stop" tab on the cap?.......No problemo amigo...........lol



Hope this helps.

Thanks for the reply. I did indeed separate them when I rebuilt them. I was going to synchronize them but couldn't get it idling so I haven't gotten to that step yet. I replaced the idle mixture screws as they were included in the rebuild kits with versions that don't have that little wing on them so I can turn them to my hearts content! When I put the carbs back in I remember seating them then turning them out two turns, but its possible they may need to come out even more (or possibly go in??) to keep them running, correct? I will reseat them then turn them out again and see if I can get it running. Thanks for the tip!



This is a picture of the kit I bought:

http://i.imgur.com/UT3tl.jpg



The new mixture screw is (I think) on the bottom row, third from the right.

Before doing that, methinks turning that big black knurled knob in between the 2 carbs to a point where the bike would STAY running without choking or blipping the throttle, would be the first point of order I would address. Because FOR SURE ya can't sync or adjust anything, IF it won't stay running.



The idle speed can ALWAYS be set lower (or higher) AFTER the carbs are synch'd.



I think the carbs should be synced at idle, but think a running up the rpms and checking is in order. Some say at idle...some say at a higher rpm as this is where you'll be running most of the time, maybe adjust to some point between the 2?...er even if that is possible?



Hope this helps ya there.





Oh ya, you can probably put those caps on (minus the wing) as the replacement screws are just a knurled brass end with a slot. Makes it easier to adjust by hand rather then trying to angle a screwdriver in a tight space.