I have a 1996 620 rxc.after sitting for a night,i can kickstart the bike,but after that it acts like there is no spark.i have good compression and a new carburator.

Is the air filter clean or no air leaks in the manifolds intake or the jets or carby haven't been damage when cleaning it or is there fuel flowing into the carby maybe fuel filter can on try

no compression
has the spark plug come loose,
could be bust piston, rings or valves,
right googled it, its a 2 stroke no valves,
moving on, your have to remove the head and barrell to see whats gone, the piston or the rings. its probably the rings.
its not as hard as it sounds on a 2 stroke so even a novice could do it.

Rock the bike gently forward and back while shifting into fifth gear. Now push the bike forward while sitting on it and see if the rear tire turning will turn the motor. If not, your motor is stuck. If it turns, you have a kickstarter issue.
Many people never learned to depress the kickstarter down until you feel it engage before kicking it through. Kicking from the top slams the gear teeth together and causes damage. You may need to pull of the engine cover to determine if there’s damage.

Does it have strong compression? If not, running it on straight gas could have done its damage. If the compression is strong, use a spray bottle to spray some fuel/oil mix directly into the throat of the carburetor. If it fires after using the spray, it means you're not getting fuel to the engine; make sure fuel is flowing from the tank. If it is, check your carburetor for gumming, clogs or stuck float.

Ok, a two stroke engine basicly needs 3 things to run: fuel, compression and ignition.

First, check that the fuelline, fuelfilter, or fueltap is not blocked. If the fuelflow is alright, check that the compression is fine. try kicking the kickstarter a few time: the should be a certain resistance.If the compression is wrong try changing the headgasket. If it is alright, check the ignition. This is done by taking the sparkplug out at placing it on the frame, when you kick the kickstarter a spark should jump from the sparkplug to the frame.

But my guess would be that you have a partly blocked fuelsystem.

I have one of these also. Push lightly on kickstart until compression is felt. Pull in the decompression lever and press kickstarter down another 2 inches, release the decompression lever, and and then let up on the kickstarter to get a full swift kick. It seems like alot to do, but once you get the hang of it, it really is easy. Also, I upgraded the copper spark plug (NGK CR8E) to an Iridium one (NGK CR8EIX) and it made it much easier also.

Also, I have heard that an exhaust cam from an ' 03 YZ450F has the same cam lobes, but with the built in auto-decompress will swap straight into this bike, I was looking into doing this with mine, but just got so good with the above procedure I did not waste the money on it.

I suspect coil / wire / spark plug cap issues. Start with plugs and plug caps. Start the bike at night and observe coils and wires . Spray coils and wires with water if necessary to look for arcing wires. If coils are bad you may have to get Accell coil kit(comes with wires and caps). Honda coils are no longer available.

There is a sequence to follow when these bikes are hot to get them started.But first.Does the bike start easily when hot if it is push started? If the answer is yes,you need to use the hot start pull switch on the carby and the get the motor in compression before you pull in the small compression lever and slowly push on the kickstarter halfway down.Release lever and fully kick the motor over from the top of the kickstarter.Don't let these bikes sit around idling.They will overheat because they need air to get through the radiator.Hope this helps

Your bike needs 4 things to run-Fuel, Spark, Air and Compression. One or some of these are missing.

1) Crank engine over several times to start. Remove spark plug. If plug is wet and smells like gas then it is getting fuel.

2) Check for spark
Put spark plug back into spark plug cap and lay spark end along side bolt or part of unpainted head making contact and crank over engine as if to start. If no spark then is electrical problem. Try changing spark plug. Check grounds. If not plug or grounds then purchase a shop manual from your local dealer and ohms test all electeical componet resistances as shop manual instructs. Be sure components do not meet specks before purchasing.

3) If has spark and plug was wet upon removal then gas has water or just old gas. If you drained the carb via bottom of carb screw into a clean clear container and see stuff at the bottom then carb is dirty with water and or dirt.

If your bike has been sitting along time condensation will build explaining water and or gas will loose its kick after sitting too long. If you think it has been sitting a long time it is best to dispose of old gas and refill with new. Water can also get into tank from gas can when fully tipped upright so dont dump every last drop into the tank...most ofter the last couple of cups are water.

If bike has been sitting for a few days and was running fine before that, turn off gas, drain carb via bottom of carb screw, close off screw and turn gas back on. This will refresh the gas in carb.

If none of these are the case and you have good fuel, good spark...check air filter for air flow. If all this is good then you need to do a compression check. A simple way to do it is to stick your finger in the spark plug hole and hold it in there with some force and have a friend try to start the bike. If it blows your finger out then it has compression. If it doesnt want to force your finger out then you have no compression and is a piston and ring problem. The only way to test compression for sure it to purchase a compression tester from auto parts store that has an adapter for your size plug hole and do a proper test. I hope this helps.

Hi!
You obviously look after your machine and very sensible when laying up, however as you are probably aware 2 strokes rely heavily on compression, A. to produce excellent combustion and B. to draw fuel into the chamber. So when you try kick starting you can't get enough revolutions to draw the correct amount of fuel into the cylinder, where as you push start you constantly turn over the engine increasing compression slightly and bingo it fires.
Can you remember how when kick starting it before this problem the feel on resistance when kicking over? has it now become a lot easier? if so you possibly have worn or broken compression piston rings.
A compression test will reveal this, I hope this sorts your query?
Press the Blue button please for my FREE effort,
Thank You!
Paul 'W' U.K.