Rough idle & Rough Running on cold starts

[Anonymous]

Hello,

When I first start my bike in the morning I have to use full choke and the bike starts fine, revs high, which has been normal. Normaly after a min or 2 of warming up, I could slowly turn the choke off and drive away. But recently, when I try to turn the choke off, it starts to cough and sputter and then stalls out. I can get it to drive off with the choke on full and then switch the choke off once I am moving, but it misses and sputters until its fully warmed up. Once its warmed up, it runs perfectly. Very smooth idle and lots of power.
Would this be a setting in the carb? Is my choke not opening or closing fully?
The only other factor I can think of, it that it has been cooler then normal here lately.

Thanks,
Jeff

[pkluss]

I'm going to hijack this thread because this is a perfect description of what is happening to my 1977 GS550. I'm brand new to the bike scene, so could you please walk me through what an experienced bike mechanic's thoughts are when this issue arises. I'm not looking to peg down the exact problem right now, but I'm always curious to see how an experienced individual arrives at the solution.

(I'm a network administrator and I often walk through my thought process when fixing a problem for someone in the hopes that it will help them better diagnose it next time. So that's where this request comes from.)

Thanks.

-pk

[chef1366]

This happened to me and I had a bad battery connection. Could also be a bad battery. If a problem suddenly appears usually it's an electrical problem.

[marvinsc]

This happened to me and I had a bad battery connection. Could also be a bad battery. If a problem suddenly appears usually it's an electrical problem.

I put a New Battery on My 850 Over the Winter and It has Made an Amazing Improvement in Starting AND Performance.

[KEITH KRAUSE]

pk, if your problem is just like Jeff's, you most likely have a dirty pilot circuit.
If you notice the warmed up idle is quite a bit higher than the cold idle, you have an intake leak.
If your idle stays within 100/200 rpm's gain from cold to hot, then your problem is fuel starvation, most likely a partially clogged pilot jet/pilot circuit passages. I'm assuming that you didn't move the side air screws or the pilot fuel screws underneath???
Playing with those screws will cause lots of trouble if you don't know how to set them.
If you do have a significant rpm rise from cold to hot, the most common cause is a leaking manifold o-ring, or sometimes the manifold itself. The o-rings should be replaced unless you know they're fairly new. They're cheap, so don't keep the old (most likely hard and flattened) o-rings in there. The manifolds are a little expensive. Check them for any cracking/hardening.