#4 is cold, oh wait, not anymore.

I started it up today and ran it with the choke for couple of minutes to warm it up. I kept feeling #4 head/jug and it was not warm so I felt the others and they were. So I did a quick tap on each header to see which cylinders where working. Looks like just #4 was not firing. Note: the exhaust was whitish. I turned off the choke and it stayed running. I reved it up a few times and held it at mid to low RPM range. (Tach not functional) I let of the gas and turned it off, and refelt the headers. All 4 are hot, #4 was not as hot as the others though. I pulled the plugs and 1, 2, 3 are all black, IE rich. Number 4 was tanish in color.

Other info: carbs just cleaned with new pilot springs, washers and o-rings. All set at 3.5 turns out. I am building a DIY manometer and YICS tool but don't have them done yet. (Looking for high temp silcon tubing and 3 or 4 way 3/16" vacuum fitting) So I know I need to tune it yet.

 

That is a common symptom of a bike with just cleaned carbs and no tuneup or colortune performed yet. If #4 was tan while the others were black I would suspect it to be lean. All should have been black since it had run with the choke on. Most likely the lean condition is due to a still clogged starter jet. This would be the one in the bottom of the float bowl. If is only needed for start up so I would worry too much about it until you get the bike tuned and see if that one runs well off the pilot & main jets.

 

I was thinking it was the carbs, it's always the carbs. I think I have read that few times...
I will probilby pull the bowl off #4 and reclean that jet. Might as well make sure everything is good to go. I may give it a seafoam treatment first to see if that clears it up. As for it running rich with the choke on, which is understandable, how long will I have to run it with the choke off inorder to clean the plugs up? That is assuming the carbs are sync'ed and tuned. Are we looking at minutes, seconds?

 

I had the same problem after a good cleaning of my carbs. Turned out that the enrichment circut on #4 was plugged. The hole in the front of the bowl that the enrichment tube lives in was not filling from the bowls main chamber. #4 wouldn't come to life until I gave it some revs, and would obviously run lean compared to cyl 1-3 when the choke was on.

Be careful when shooting carb cleaner through this circuit. It will go exactly where the opposite end is aimed and travel a good distance with incredible preciscion. For me, it was first my eye and then the windshield on my snowmobile.

 

Haha, i think this happens to everyone at least once. I seriously can not over-state how painful carb cleaner is when it meets your eye. Wear goggles, please!