Carb Issue Resolved

[Dan Filetti]

So, I wound up doing a 'light clean' on the Ninja 250 carbs over the weekend.  I had run it earlier in the day, and it ran well.  But on the way home, while riding, it stalled at the top of my driveway [convenient!] like it was fuel starved. I knew I had fuel but I switched over to the reserve and tried to fire it up. It would spin but not light. I coasted it back down to the garage to give it a look.  The tank is free of rust.  If there is a fuel filter, it's inside the tank.

Seeing that there was decent fuel delivery to the carbs, knowing this bike's carbs are especially sensitive to sitting, (been neglecting the old girl favoring the Gixxer) and that the gas in it was perhaps 2 months old, I suspected the carbs were gummed. This is especially true given this new ethanol gas, which it seems, tends to rot when it sits for more than like a minute... So, I had done this once before on this bike a few years ago. When I bought it, it was not running due to gummed carbs -which made it significantly cheaper to buy!! This time they looked similar to what they had looked like before, when I got them open -definite signs of gumage.   

I popped the carbs off, (easy as pie to work on -let me tell you) pulled the bowls off, removed the jets, cleaned them out with carb cleaner and compressed air. As before I did not break the racks apart, I just did not see the need as especially, this procedure had worked perfectly, right after I bought the bike. This time, after re-installing the carbs, and replacing the gas, the bike fired up immediately and ran really well. Feeling proud of myself, I put the bike back together the rest of the way.

Now, on the test ride, the bike rode flawlessly, except, there was a problem with the idle. It would idle fine until it warmed up. Once the choke was off though, the RPM would slowly dwindle, over say a minute, until it stalled. Started right back up though. If I turned the idle up and blip the throttle it would increase rested idle rpm, but still the same thing with the dwindle/ stall. If I kept turning the idle up it continued as above until it got so high, the idle hung at roughly 2,500 rpm, with no more dwindling.  I could not find a happy medium despite trying several times.

So after some tinkering, I figured it out.  I did this by trying to spray starter fluid around the intake boots.  Doing so got the motor revving up so I knew I was on to something.  So now I knew I had a leak/ lean condition. Turns out all I needed to do was ensure that the intake boots were seated properly.  So I went back and re-seated the intake boots and she purrs like kitten now. 

I suspect that this is directly translatable to the FJ.  If, after having removed and re-installed your carbs you get a dwindling idle/ then stall, first check that you do not have an intake leak.

FYI,

Dan

[Pat Conlon]

Good tip Dan. Thanks for the experimentation and explanation!

That is exactly what happened to me. I finally R&R'ed the carbs and the problem went away.... 

I'm scratching my head thinking....Hmmm, friggin FJ carbs are haunted. 
I never did figure out the problem, it just went away. Now I know what I did wrong. (I suspect I'm not alone) I like to feel the click as the carbs get seated in the intake boots, a hair dryer to soften them up and a light smear of silicone grease helps on old boots.

Dan...Before this little nugget gets buried, would you mind if I copy and pasted this tip over in the Files (carb) section?  Cheers!  Pat

[Dan Filetti]

Feel free to copy/ paste any-old-place!

Thanks,

Dan