Stalling when downshifting-only happens in first 5 min
 

I just bought my first bike, an 06 Ninja 250. My bike stalls when I downshift from 2nd to 1st, but only in the first 5-10 minutes of start-up. I have to have the choke on during this 5-10 minutes too or the bike stalls. If I don't have the choke engaged and try to roll on the throttle, the bike stalls. Once the engine warms up it stops stalling. The RPMs are too low when I start it I think. Have any of you had this problem? The carburetor was just cleaned, so it shouldn't be a problem with that. They cleaned the fuel passages and jetting and installed new spark plugs too.

I know questions on this have been answered before, but I just wanted to ask because I'm a college student and don't have much money to spend and I'm trying to pinpoint the problem. I also have zero knowledge about how motorcycles work, so I doubt I could fix anything myself.

Welcome to the forums, jrt. Some carbureted Kaw's (including mine) need to warm up before things work properly. (And, honestly, it's not a bad thing to warm the engine just a bit before you get going.) I'm guessing the gearbox may "clunk" a bit during the first 5-10 minutes as well? Your bike is probably fine, mechanically. Get used to needing an extra 5 minutes to get going. I've been doing this for years.
Glad to have you with us. Gear up; stay safe.

Now that I think about it the gearbox does seem a bit clunky for around 10 minutes. I've ridden a few different bikes before and I could ride those right away, so I just assumed something could be wrong. Thanks.

What idle speed are you running? oil? and are you sure that the clutch play is per the manual?

Welcome to KF

In my case, trust me; I've been through my 9 with a fine tooth comb. Give the bike 5 minutes, and it's a happy camper. Mysteries of the universe.......

It's idle speed without me having to use the choke is around a 1000 when I start it up. But after it warms up and I disengage the choke it's a bit higher (1300ish I think). I'll probably try to raise that a bit tomorrow when I have more time. The engine is supposed to be warmed up when I try to raise the idle speed right? Should it just require a small turn on the knob?

Oil is fine. What exactly do you mean by clutch play? The clutch seems fine.

just asking on the clutch play and engagement. you need some carb work and synch done. As in a good soak and tune. What is your elevation?

(Or, just do your bike a favor and let it warm up a few minutes....) ;)

Taken from CarGather.com. (Yes, oriented toward carbureted car engines, but the physics are bacially the same.) A few thoughts on "cylinder washing" on a cold engine before everything gets warm and friendly:

"These are all good points, but we keep dancing around the full story. On carbureted engines, idling them until they're warm is a convenience to drivability. It is true that the exessively rich (sometimes 5:1) mixtures will wash down cylinder walls, but keep in mind that at no load idle (especially fast idle) places almost NO load on the cylinder walls. There is little combustion chamber pressure forcing ring seal, so the wear in neglegible. What DOES kill these carbed engines is the excessive oil dilution from the poor ring seal and washed walls letting excessive gasoline into the oil. This was the original cause for concern on vehicles that were used for short distances, and the proliferation of the sales pitch, "highway miles." On short trip cars, the oil continually stayed diluted, but on highway cars, the oil reached temps that evaporated the junk out of the oil. The reason for the excessively rich mixtures, as we all know, was that the cold walls of the intake condensed the fuel making sheets of fuel break off and get sucked in. The high idle was to counteract the volatile nature of the mixture. Driving a carbureted car before it was warm did two things that sucked; 1) The excessively rich mixture washing down the walls, plus the load placed on the engine meant you had optimum ring-to-wall pressure, without the oil present to prevent cylinder wear. 2) Operating the accelerator pedal meant operating the accelerator pump, further exaggerating the rich mixture."

I just had the carbs cleaned up a couple weeks ago. And I'm at a few hundred feet.