95 model thunderbird, runs great until idle, cuts out no spark bike starts again when it feels like it. when idling engine randomly miss fires as if you were flicking the kill switch on and off quickly. have fittered a new ignter box and bridged side stand switch

Check your tank vent. Ride the bike until it stalls, pull over and pop open the gas tank lid. If you hear a "ffffwwwwwah" of air being sucked in when you open the tank, your air vent is blocked. The bike runs great when you start out, but as fuel is taken out of the tank no air can get in to replace it and the tank develops a vacuum.

The idle speed will be dependent on model, particularly if 4- or 2-cycle, 2, 4, 6 cylinders, etc. If your engine uses carburetors, I'd say no less than 600 RPM, maybe up to 850 RPM at idle. If your engine is fuel injected, the computer should set the idle speed and air mixture for you (if it's functioning correctly), and a big twin could idle as high as 1150 RPM .

Your Idle air mixture settings are important for proper idle. A good approach is to let the engine tell you what it likes. For this method you will need either a tachometer or a vacuum gauge. Here are some steps to guide you.

1) If the engine will start and run, go from there. If not, a good initial setting is to turn the idle screw(s) all the way in (GENTLY--don't break the seats!), then back them out about 1 1/2 to 2 1/2 turns.
2) Attach either your tachometer or vacuum gauge to your engine. Tach is connected to the ignition system (usually at the coil); vacuum gauge would be connected to a manifold vacuum port. (The bike's built-in tach MAY work for this, but they are often not graduated finely enough.)
3) If using a tachometer, warm up the engine. Working on only one idle mixture screw at a time, begin turning it IN until RPM begins to decrease. Then back the screw OUT again until you achieve maximum RPM on that screw. Feel free to "play," turning the screw in and out until you achieve highest RPM at at minimum turn-out (if you leave it turned out too far, bike will run rich and foul spark plugs; if not far enough, bike will run lean and hot). Now do the other idle mixture screws the same way. Finally, go back and do all the mixture screws again (and again and again, if necessary) until all throttle bores are synchronized.
4) If using a vacuum gauge, engine temp is not as critical, but go ahead and warm it up anyway. Similarly to the tachometer method, turn the mixture screws in until RPM drops, then out until max vacuum reading at minimum turn-out. If you have multiple mixture screws, do the same on each, then repeat on all screws until you feel they are all synchronized.
5) Throughout the process of adjusting idle air mixture screws, you will probably have to adjust the idle screws to keep the engine in the RPM range you want it to idle. (If adjusting air mixture screws has no effect on the engine idle, the minimum requirement is probably a carburetor rebuild.)
6) Have fun getting to know what your engine "likes!"

Something like this is often a stuck or poorly sealing valve. A Vacuum gauge is the least obtrusive way to notice vacuum changes. If a cylinder fails to seal, vacuum will reflect the loss of compression and it will result in a bounce on the meter.

Hi Jason:
A Random/Multiple Cylinder Misfire Detected unfortunately doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

A code Random/Multiple Cylinder Misfire Detected may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

Possible Solutions:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

COMMON FAULT, FLOAT IN CARB CAN STICK CAUSING FUEL STARVATION REMOVE FUEL BOWL CHECK THE FLOATS FOR FREE MOVMENT {WD40} DOES THE BIKE START THEN CUT OUT OR ONLY RUN WHEN THROTTLE TURNED AND NOT IDLE. IDLE JET IN CARB COULD BE BLOCK WITH DIRT , IF DOES NOT START AT ALL CHECK YOU HAVE SPARK AT PLUG ,REMOVE PLUG FROM HEAD PUT INTO HT LEAD HOLD AGAINST ENGINE HEAD TURN ENGINE OVER YOU WILL SEE SPARK {IF YOUR UNLUCKY YOU,LL FEEL IT } HOPE YOU SORT IT OUT GOOD LUCK {FROM AN AUTO ELECTRICIAN]

The two carbs are not balanced to each other. Balance as follows; Start the bike then increase the idle on the left carb to a high idle. Now unplug the right cylinder and the engine will slow down some. Now slowly turn the idle down on the left carb until the engine just dies. Hook up the right plug wire then do the same proceedure for the right carb. Now both carbs are balanced. Hook up the left wire and start the engine again. The bike will be running faster than you want so now adjust the idle screws on both carbs equally to get the desired idle speed. Please rate my answer. Thanks.

DRAIN CARBS FROM PETCOCK AT BOTTOM OF EACH CARB MAKE SURE FUEL DRAINS COMPLETELY THEN TURN FUEL BACK ON, IF THIS IS AN INJECTED MODEL DRAIN TANK AND FLUSH THEN RUN IT HARD FOR 20 MILES OR SO, MAKE SURE YOUR OIL LEVEL IS OK

If you need further help, I’m available over the phone at https://www.6ya.com/expert/michael_00678fd4800d19c5

hi there, have you cleaned the carb lately? i have a honda anf 125, a tad bigger that a 100. anyways, usually a mis-tuned or dirty carb makes the idle of our bike go crazy. If your a do-it-yourselfer, dismantling the carb and cleaning the jets, air ports, and choke lines would be best. Not to mention replacing the fuel filter if you have one in series with the fuel line. If you have cleaned the carb and installed it back to the bike, tuning is next. don't worry if you don't know the right position of the air-fuel screw w/c is next to the idle screw. Turn the air-fuel screw clockwise until it stops. Remember the position of the screw. Turn the idle screw clockwise a few turns until you see the throttle piston moves upward a bit. Then, start the bike. Turn the idle screw until the bike is running without stalling(higher than idle rpm. just like the bike is cruising about 40kph) . Now its time for the tuning. Turn the air-fuel screw counter-clockwise count your turns while listening to the sound of the engine. You will will hear the engine runs smoother and the the rpm starts getting higher also. Stop when you do not hear anymore significant change. Then turn the air-fuel screw clockwise a little about 1/8 turn then stop. Slowly turn the idle screw counter clockwise until you reach 1200 or 1400 rpm (well thats the standard value). Now, try revving the engine, if the engine looses power at the high rpm, turn the air-fuel screw 1/8 clockwise more. Do this step until the pooot-pooting stops. Try the bike and feel the power. If it feels the bike is back in shape. try using the bike for a few weeks. After a week, remove the spark plug and look at the tip. If the tip of your spark plug is kinda grayish or slightly redish(depends on the type of petrol you're using). You're setting is good to go. If the tip color is dark gray to black, the setting is to rich. turn the air-fuel screw counterclockwise about 1/8 turn, then test again. if no color change occurs well the engine should be checked and that's another story.

Hope this helps. More power!

The "mechanic" who told you that is lying or stupid. Bikes come from the factory set to run properly, not miss and cut out. The first thing you need to do is find a different mechanic. I would try some different gasoline, perhaps add some "Seafoam", check the spark plugs and spark plug wires, and look for vacuum leaks. Good luck.

i recommend checking out your plugs and wires. If you take out any of the spark plugs look at their condition and compare them to each other if there is one darker or wetter than the others that is the one that is misfiring causing the vibration and difficulty in starting.