motorbike crank but no ignition 3?

Question

im really new to motorbikes, so any help would be greatly appreciated.
i have a honda cm125 four stroke.today my bike died whilst i was driving it, about 10miles into a journey, and refused to start. it won't kick start, and won't even bump start. the engine cranks, but thats it. and it didn't just stall, there was a loss of power- i noticed it slowing down- and then slowly came to a halt. but lights, horn, etc work, and the starter motor turns.
what could it be? the KILL switch is on RUN, it has a new spark plug, and it sparks.it has a full tank of fresh fuel, and the spark plug is wet when i crank it.it makes no difference if the choke is on or if the petcock is on prime or reserve. the battery is fully charged, and connected.the carbs are clean, i can see through the jets, ive checked the valves, there is compression, the fuel lines are clean, and i don't have a kickstand switch.

WHAT THE HELL IS IT!?!

any answers appreciated

thanks!

oh, and the fuel filter is clean. and ive tried washing the air filter and running it without one-no difference.

Answer 1

Always give year, make, engine size and model # when asking questions. We need "all" of that info to give an informed answer.
From your description, it sounds like an electrical problem. Check for spark.
--Remove the spark plug.
--Insert it into the spark plug cap.
--Lay the threads of the spark plug on the motor.
--Turn on the key, kill switch on run and push the starter button.
--If no spark, it could be the pulse generator (pick up coil), ignition coil, high tension lead not making a good connection to the spark plug cap, or bad spark plug cap.
--First try - unscrew the spark plug cap from the wire, cut 1/4" off the end of the wire, screw the cap back on and check for spark again.
--If you still can't figure out the problem, you can bring your bike to a mechanic and spend over $150, or buy a shop manual for $50 and follow the trouble shooting instructions.
http://www.motocom.com/motorcycles/

Answer 2

If you have checked that a spark is present and your sure fuel is getting through, assuming you have not been 'tickering' with the electrics. I would say you ignition timeing has come lose and the static plate has been slowly moving (hence the loss of power over short period).
I would get the timing checked (an owners manual will tell you how to do this).
Also check theres no water in the carberator (as an outside chance).
Hope that helps.

Answer 3

It could be the starter solenoid, If it is then you will need a mechanic to fix it. It could be because the engine is flooding. Try turning the engine over with the spark plug removed and choke off. If that doesent help squirt some fuel into the cilinders and try starting it. Hope this helps thanks

Answer 4

Bad coil, check the regulator too, heck it could have an old magnito on it to. Your getting power, also does your bike run on points, if so have you ever advanced them, are you getting a spark, check to see if the coils is allowing a spark to generate threw the system.

Answer 5

Do you have oil in the crank case?(could have lost a crank bearing)2.Could have burned diode in rectifier.Generally a slowing down could indicate a rod bearing going out.

Answer 6

The ignition coil - been there done that 200 times

Answer 7

i notice you say carbs so its got to be a twin,my guess is the head gasket small blow between the cylinders,try a compression tester.

Answer 8

Check your ignition, kill switch. It is by the throttle and may have been activated by accident.

Answer 9

not being funny but it has got fresh fuel in it?