In article <97z5=sf@rpi.edu> chungy2@aix.rpi.edu (Yau Felix Chung) writes: > >I am having trouble starting (keeping running) my 1992 CBR600F2.  I have >had problems with it since last year, but it seemed to have subsided.  Now >it's back again.  Problem persists regardless of choke usage pattern, >gasoline type (brand & octane) and pretty much anything else I can imagine >to change.  The dealer is stumped (it's still under warranty). > >I start the bike.  It runs great for a while (45-90 seconds) then the engine >starts to slow down.  DECREASING the idle setting will INCREASE the engine >speed.  INCREASING the choke INCREASES the engine speed.  Regardless, the >engine will eventually slow down (and stop).   > >Once stopped, it will not restart (even after flooded engine drill).  If >I let it sit (45-90 minutes) it starts beautifully and runs great for ever. >So I go out, ride it hard for 100 miles and bring it back, ride it easy  >for a few miles to let it cool down, and put it away. > >Next day, I go thru the same drill to get it going. > >Any ideas?  Has anyone seen this before?  Another F2 rider had similiar problems, and this is the mail I sent him, hope this helps resolve you problem!  AT   >  > Allen Tobias writes: >  > Check the vent tube to the tank. Sometimes the tube is clogged or constricted. >  > This prevents gas from flowing into the carbs because of the vacuum created by >  > the displacement of the gasoline. This is the small tube on the bottom of the  >  > tank, the large tube is the overflow. You will have to remove the left side >  > tail section to get access to this area.  >  >  >  > Good Luck! >  >  > but if it was clogged, wouldn't this interfere with engine operation all > the time ? When it runs, it runs well.  >  Good point, did not catch this in the original post. The only other things  which come to mind, since this is a gravity feed fuel system, is this. The fuel petcock valve is vacuum controlled from the #1 carburator. Let suppose there is a small hole or bad seal either in the hose itself or the vacuum valve in the fuel petcock. When it is cold, the hole is open enough to open the valve just enough to allow gas to the carbs with the choke on,  since the choke creates more low pressure in the carbs when on to draw gas,  and as the engine and surrounding area warm up, the hole seals up.   One way to check fuel flow through the valve would be to pull the side  panels off and remove the fuel hose to the carbs. Connect a tube of the  correct size, preferably clear tubing to observe fuel flow, on the output side of the fuel petcock. Remove the control hose from #1 carburator. Make sure the tank is full. Place the valve in the ON position and apply vacuum  to the control hose, preferably with a vacuum device with a gauge, to check  for air leaks. With vacuum applied, fuel should flow freely. To see if there is a vent problem, do this with the fuel filler cap open and closed, if it  flows a lot faster with the filler cap open, then there may be something in  the vent airway which changes position and depending on the position may clog  or partially clog the vent. I have heard of some F2 fuel tanks being replaced  to fix this problem. So the things which might be defective are, the control hose from #1 carb, the petcock valve, and possibly the fuel tank vent.  Now if all of the above shows no problem of fuel flow when cold, then there  is something in the carbs screwed up, but there are so many things to check,  I would be typing all day to list them all!   Here are a few, with everything back together, apply vacuum to the petcock valve and open the drain holes on the carbs one by one to check fuel flow. Open up the airbox and check for foreign debris or clogged airways on the carbs, there are quite a few on each carb.  I hope something is flushed out with all this trouble shooting. If American Honda does not resolve this, get MAD AS HELL and report them to the BBB and call the Honda Customer Service HOTLINE. It is a 800 number, but I don't recall it off the top of my head. I called just about tires for my F2 and a few days later a customer satisfaction inquiry card arrived at home asking how I liked the support I received, here would be your chance to tell them what you think!