Carb won't rev

[eamartin]

Super 8 2t.  Sat for a long time.  Cleaned the jets and remainder of fuel system.  Fresh gas.  It ran but would stop after a few seconds.  Pulled the carb.  Carb looks super clean.  Verified all passages open with WD40, small brush, small broach or flashlight. Installed the carb and rode or ran the bike every day for a week.  Then, one day I started it,  after the 3-4 minutes the bystarter would do it's thing and close the enrichening circuit, the carb would idle down fine.  But if I give it gas, it dies.  It will start again okay, but I cannot rev it.  It dies.  Every day it starts fine, idles high while the enrichening circuit is open and I can rev it up until it's warmed up and the enrichening circuit is closed.  From the symptoms, it would seem that the idle circuit is partially blocked.  The passage from the idle jet to the carb throat has two 90 degree turns, so there is one turn I cannot see or get a cleaning brush to.  Like I said,  at one point it was running well and all of a sudden, it was not.  Are there any other problems which might show these symptoms?  I have the carb boy submerged in carb cleaner.  After that I may do an ultrasonic cleaning to it. 

[eamartin]

Shortly after my last post I submerged all the carb parts in carb cleaner for 24 hours.  After cleaning and allowing the parts to dry, I cleaned the carb body in an ultrasonic cleaner.   After re-assembling and installing, the bike ran fine, it revved properly and has worked well ever since.

[Mr. Paul]

Thanks for the update! I have had the same problem, more than once. I am getting pretty good at removing and cleaning the carbs. Sometimes I just turn them upside down and clean the jets while it is still attached.

[eamartin]

Mr. Paul,  My suspicion is that there were 2 idle circuit places which might have been the source of a fuel restriction preventing fuel just "off idle".  Both were places I could not visually inspect.  I mentioned the first, the idle passage with two 90 degree turns.  The second was the idle jet.  I could see reflected light through the passage bends and I felt pretty confident that it was quite clear.  And while I could see direct bright light through the idle jet, there were times when I thought that maybe I could see something on the edge of that light.  Since the hole on the emulsion tube side of the idle jet is quite a bit larger than the jet hole, I thought that there could conceivably be piece of debris attached inside the emulsion tube but somehow flapping against the jet hole blocking the passage when air and fuel passed by.  For me, it is impossible to see into this end of the idle jet for inspection of the walls.  So before re-cleaning the carb I whittled down a toothpick to clean the inside walls, break loose anything that might be attached.  Then I submerged the carb as I usually do and so far, so good.  The bike's been running correctly. That's my story.