I have a 1996 Honda CB500 four-cylinder motorcycle with 21,000 miles on it that I bought new. I obviously have not ridden it a lot, but it has always started on the first crank and idled quietly at 1000 rpm. The only problem I was having with it was sometimes the carburetors would overflow gas when I shut it down. So I took it to the only repair shop in Augusta, GA that works on these old Hondas. They had it all last summer and it has not run right since. Although he said he replaced the needle valves and seats, it still leaks gas and now if the idle falls below 2500 rpm it dies, and it does not want to start without ether. I use to start it with the choke on and then in about 30 seconds open the coke fully. If I left it closed the engine would chug or die. Now, no matter what temperature it is, it idles much faster 5500 rpm with the choke closed. This is what I have checked: Points: OK Timing: OK Float level adjustments: they may not be perfect, but they are close. Vacuum: (I have the Honda vacuum gauge set) The vacuum is supposed to be 20 inches Hg at 1000 rpm, but since I cannot get it to run at 1000 rpm I checked the vacuum at 3000 rpm. They ranged from 4 to 5 inches Hg. I can adjust any one carburetor down to 20 inches, but not more than one at a time without it dying. I ended up setting them all at 7 inches Hg. Idle Mixture: Screws were originally open 1.5 turns which are spec, but I was able to get the idle down from 3000 to 2500 rpm by adjusting them all to 1.75 turns more there way did not help. There is no problem with the gas tank vent. Choke position: I even took the inlet manifold off and verified that the choke plates were closed when the lever was in the closed position. Does anyone know what is wrong with this bike?@
Don't know what your last mechanic did but if you have any confidence in him take it back and have the carbs cleaned and adjusted.There may be obstructions.Other than that I would take the carbs off and ship them to a good shop.
SOURCE: 99 olds alero 2.4
I'm sure you have installed a fuel pressure gauge and monitored the fuel pressure while the problem is occurring?Another diagnostic tool which is easy to do,is while the problem is occurring,unplug one sensor at a time beginning with the Mass Air Flow first,.if it uses one.Many times,not always,depending on the sensor,if the sensor is taken out of the picture as far as what the PCM is seeing,like unplugging the MAF,the PCM will substitute the missing sensor output with a generic value that will allow the engine to at least run,and if unplugging for example the MAF,the engine idle speed returns to normal,you know you're onto the problem.You didn't mention if the engine ran ok other than the idle problem.As far as checking for vacuum leaks,i use something like brake cleaner or WD 40,more of a liquid,and it does sound like a vacuum leak.Plastic intake manifolds do develop nearly invisible cracks that open up more with heat.Revsisit the possibility.And as for the PCM,it is possible,but more likely a mechanical problem.Lastly,remove an O2 sensor or two before the catalytic convertor,run the engine and see if anything changes.Cheap way to verify the catalytic convertor is flowing and not restricting engine airflow,as i have seen bad cats cause misfire codes and strange problems.Good luck.
SOURCE: my 2009 ninja 250r starts but dies when you remove
I had the same problem.. choke cable had to be adjusted. Check the manual, I don't have mine handy but the measurement is in there.. check it out.
SOURCE: 1984 CT110 won't idle consistently
On most bikes, opening the pilot needle screw actually leans the mixture , as it is an air screw, not a fuel screw. I'm not for sure that this is the case in your bike, but if you can find out exactly what carb it has, I can tell you. Also, a freshly rebuilt engine is going to idle erraticaly until the rings are seated and broken in. Be sure to check your carb boots and vaccum lines for cracks and leaks, as a vaccum leak can cause a lean condition.
Sarge
SOURCE: This is a 3 wheeler 125 m honda one cyl runs
Sounds like a loose piece of crud in the main jet. Have you had the jet and tube above it out? It could also be a spark problem. See if you have spark when it tries to die ( put a nail in the plug boot and get it sparking 1/4" or so to the plug at idle then rev it up, it should continue jumping. I think that bike will also have mechanical spark advance on the rotor on the end of the cam. If the springs are loose on that the spark timing will be all over the map and can make it run intermittantly.
Jordan
SOURCE: I have a Hobart Welder with a Kohler Engine CH20.
Ever try draining the carb ? it may have sediment in it.
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