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Old September 13th, 2020, 02:47 PM   #1
crimsondragon member
Name: Tim
Location: NJ
Join Date: Sep 2013

Motorcycle(s): 2006 Ninja 250

Posts: 41
one cylinder richer than the other

I have a carburetor issue going on (don't most of us do?). The backstory is the bike was sitting in my garage for a while and with the pandemic, it has given me time to revive it. So long story short, I cleaned the carbs out multiple times due to one issue or the other, rebuilt it with new float bowl gasket, new idle mixture screws, o-rings, spring, and washer, and new float needles. I finally had it running great like a month ago.

Did a small road trip to pick up mail at my gf's place, about 60 miles away, then went to my mom's to pick up old mail, about 30 miles away, then on the way home, I lost all power while on the highway and could not rev past 6k RPM and had a real tough time going above 50 mph. I was able to limp it home and I cleaned the carb again. Honestly, no real findings but I did notice my air filter was disintegrated, so I replaced that with a stock style UNI. I took it for a test ride and it was hard to idle when warmed up. I played with the idle screws a bit and right now I currently have it idling decent while warm but it has a hell of a time starting when cold. This wasn't an issue when it was running great.

So my current issue is I have cylinder 1 running much richer at idle than cylinder 2. There was a misfire for sure and with the bike running at idle warmed up (fans kicking on), I have to set the idle screws at 1 turn out on 2 and like half a turn out on 1 for the misfire to go away. I've pulled the plugs to verify this. #2 is a good brown color but #1 is black. I've done a compression test and it is 155 on both cylinders. Checked spark and it fires right. Checked valve timing and it is at the limits of loose where I last set it.

I have a dynojet kit and I theorized that when I put the new filter in, it threw off the jetting so I stepped down the needle height one notch so its on the 3rd notch. I've also set the float height to 19mm, which is also the limit of what the service manual says. I thought maybe the coasting enricher is at fault but I took it apart and the o-ring and diaphragm looks good. Plus I think the design of the enricher throws fuel in both carbs if there is enough vacuum. What else can cause one side of the carb to dump more fuel than the other? Thanks in advance.
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