no starter problems...?

Question

i have a Honda CM125 four stroke with CDI.

the bike was having trouble starting-just clicked under the seat and didn't crank- but bump started fine.
i put WD40 on the contacts- ran perfectly.

10miles in it stopped.

it wouldn't bump start.lights ect. work, KILL switch is on RUN, fresh fuel, checked contacts, fuel lines ect....NO STARTER.

it cranks but won't fire.

but the spark plugs fires-weakly.not nice and fat and blue.

i replaced the spark plug and battery-no difference.

im pretty certain its electrical-but what is it?

it doesn't have points by the way...

Answer 1

If your bike has CDI, it will not have points, so there should be few problems with that.

Initially it sounds like a low voltage problem, usually caused by a bad battery, but you've said that you replaced that already. With electric start vehicles with CDI, you will need a small amount of voltage to operate the ignition system with while the starter is cranking. Usually this is ruled out if the bike can be bump started, but you've ruled that out as well.

It does sound like an ignition symptom to me and you're correct in starting with the connectors, making sure they are clean, dry, and that there aren't any intermittent loose connections behind the plugs.

You can also check the ignition coil resistance, making sure it's neither shorted nor completely open, but coils are pretty reliable.

Of course the obvious place to check would also be the fuses, making sure they're clean, not corroded, dry and not blown.

Beyond these simple external things, you will want to pick up a service manual and work the problem from the trigger to the plug, checking each component for proper resistance and each wire for continuity.

On a dis-related motorcycle (Yamaha) we had a similar problem years ago and it turned out to be a faulty voltage regulator. Just a thought.

In the meantime, read the link I've included below and good luck finding the problem...

Answer 2

right the click under the seat is the starter solenoid, t but thats ok now as will crank over, WE KNOW ITS NOT YOUR POINTS AS YOU SAY IN YOUR QUESTION ITS "CDI",
you have a week spark could be coil ,

but as you have had other power related faults ,i would go for an earthing problem corroded earth contacts, try clean them up that involves undoing them then clean crud off bolts & earth contact,
start with both ends of battery terminal one end will proberbaly bolt to back of engine, make sure you tighten them up properly,

mfactor says it might be charge prob, quick way to check that with out a meter is put bike in front of a wall start & turn lights on, then rev bike the light beam should get brighter when you first rev from tick over then will dim as drops back to tick over,
this tells you the generator is working but not what is coming through the reg rectifier,

Answer 3

regulator/rectifier , it sounds like its running off the battery for the 10 miles then stopping, put an electrical tester across the battery terminals and rev the bike a bit, you should see at least 13 volts going in, less than 12 and its not charging so you will need a regulator/rectifier.

Answer 4

Coil pack, wiring or crank sensor

Answer 5

Your points could be worn out and the WD40 just gave a temporary solution ?, try running some very fine sandpaper between the points and see if that helps ?.

Answer 6

it sounds like your coil to me, however I'm not that good when electrics are concerned

Answer 7

sounds like the coil to me

Answer 8

If it's an older bike and has points then it sounds like they either need adjustment or replacement.

Answer 9

coil

Answer 10

due to cold weather