Hi there fellas, new to the forum and hoping for some good advice. I figured I would ask since I am about to pull my hair out over this damn bike. So, I am trying to get this little bike up and running for a friend. Put a good battery in the bike, I have power to all of the lights, ignition switch works just fine, run stop switch also works. I crank over the bike and I get ac voltage out of the stator. I have power to the black/white wire at the ignition coil but I have no spark. I have tried 4 different coils, cleaned the points and tried 2 different condensers. I have traced and re-traced the wiring diagram 100 times and I can't figure out why I am not getting and fire at the plugs. Any help is very much appreciated.
I know my CT90 will not start without a battery. You said you changed that with a new one. Check your stops.
I'd try to jumper from the battery to the Positive side of the coil bypassing the wiring and switches and see if it works, if it does you'll need to figure out what's wrong with the wiring,
Also check your rectifier. I've never messed with one on any of my CTs or STs, but I've read that it won't run with a bad one. Since your lights work...I dunno.
I'd try to jumper from the battery to the Positive side of the coil bypassing the wiring and switches and see if it works, if it does you'll need to figure out what's wrong with the wiring,
Also check your rectifier. I've never messed with one on any of my CTs or STs, but I've read that it won't run with a bad one. Since your lights work...I dunno.
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No, I have not checked the kill switch besides the fact that when it's off I have no power to the black/white wire to the coil and when it's on run it goes back to battery voltage. Is there another test I should be doing to that particular switch? Also, the neutral light is inop, as well as the tail light and the signals stay on constantly without flashing. I would of mentioned these things earlier but I figured they were isolated issues and my main problem is the no spark.
Also, when I said I had stator output I meant that at the pink wire to the rectifier i was getting ac voltage spikes as I kicked over the bike. I am not sure that it is within the "spec" of the service manual but I figured I was ok. Does that rectifier play a part into this issue? I have re-checked my grounds and set my points gap again without any luck. Please help!
I didn't see it mentioned that you replaced the spark plug itself. It is possible for that to go bad, so if you haven't done that, I would try it.
Also check the flywheel "key", as if the flywheel spins on the shaft because of a sheared key, it can spin to a point where it isn't firing at the proper time to spark the spark plug. I had that happen to my Suzuki RV90, and it drove me nuts for a while. Until I realized it
Also check the flywheel "key", as if the flywheel spins on the shaft because of a sheared key, it can spin to a point where it isn't firing at the proper time to spark the spark plug. I had that happen to my Suzuki RV90, and it drove me nuts for a while. Until I realized it
The ST90 has battery-powered ignition, and the bike needs a charged battery to make a decent spark at kickover. A good 6 Volt wet cell battery will measure 6.3 Volts fully charged, and a few tenths of a Volt higher if the "topcharge" has not been used up.
First test, check for DC Volts at the points. Using the kickstarter, rotate the engine through until the points open (the points should be gapped to .012") and measure the DC Volts. This test is done with the ignition switch ON and the kill switch set to "RUN". Measure DC Volts between the engine block and the part of the points that moves. This should measure slightly less than the Voltage at the battery.
The points have to be super clean. I use electrical contact cleaner made by Caig, however brake parts cleaner is pretty good. With the points closed, drag a piece of clean paper between the points to burnish them clean. Check the gap by opening the points and using a clean feeler gauge between them.
Ground connections give trouble on these bikes over time. The battery negative wire terminal is "grounded" to the chassis at a bolt. The ignition coil and condenser are grounded to the chassis with bolts. The engine bloack is grounded to the chassis with bolts. The points are grounded to the points plate, which grounds to the head, which grounds to the block. Depending on corrosion levels, you may need to service the ground connections.
The wiring on these bikes gives trouble over time with corrosion. The 3.5mm male and female connectors corrode over time and cause lots of problems. Even if a connector "looks good" you should dismantle it and use Caig's DeOxite and Q-Tips to clean both connectors. Smear a dab of silicon dielectric grease on these to prevent future corrosion, and you can eliminate the wiring as a possible problem.
The coils on these bikes hardly EVER fail. Keep in mind, these bikes require a battery-powered 6 Volt coil. An AC magneto coil from another Honda will not work. A 12 Volt battery-operated coil will also not work. You can run a CT90, S90, ar another ST90 coil. JC Whitney has a 6 Volt generic coil that works, and the 6 Volt Volkwagen Beetle coil works - but mounting it is tough to do.
The spark plug wires tend to erode up inside the wire where the plug boot threads on. Remove boot, trim the spark plug wire back unitl fresh metal wire shows, and thread the boot on. You can get a spark plug wire splicer kit if the spark plug wire is too far gone, since the wire is embedded in the ignition coil.
The spark plug boots fail OFTEN. Many had a resistor inside that burns out. Replace with a non-resistor boot only if you use no electronics near the bike.
As mentioned, the spark plug is problematic. I have seen more spark plugs for these engines defective right out of the box, than any other plug. Its the narrow construction perhaps.
If you think the grounds are bad, you can use jumper leads to connect the battery ground wire to the coil mount and cylinder head for a test.
The ignition switches sometimes fail, or develop resistance and resulting Voltage drop issues.
Hope something in here helps.
First test, check for DC Volts at the points. Using the kickstarter, rotate the engine through until the points open (the points should be gapped to .012") and measure the DC Volts. This test is done with the ignition switch ON and the kill switch set to "RUN". Measure DC Volts between the engine block and the part of the points that moves. This should measure slightly less than the Voltage at the battery.
The points have to be super clean. I use electrical contact cleaner made by Caig, however brake parts cleaner is pretty good. With the points closed, drag a piece of clean paper between the points to burnish them clean. Check the gap by opening the points and using a clean feeler gauge between them.
Ground connections give trouble on these bikes over time. The battery negative wire terminal is "grounded" to the chassis at a bolt. The ignition coil and condenser are grounded to the chassis with bolts. The engine bloack is grounded to the chassis with bolts. The points are grounded to the points plate, which grounds to the head, which grounds to the block. Depending on corrosion levels, you may need to service the ground connections.
The wiring on these bikes gives trouble over time with corrosion. The 3.5mm male and female connectors corrode over time and cause lots of problems. Even if a connector "looks good" you should dismantle it and use Caig's DeOxite and Q-Tips to clean both connectors. Smear a dab of silicon dielectric grease on these to prevent future corrosion, and you can eliminate the wiring as a possible problem.
The coils on these bikes hardly EVER fail. Keep in mind, these bikes require a battery-powered 6 Volt coil. An AC magneto coil from another Honda will not work. A 12 Volt battery-operated coil will also not work. You can run a CT90, S90, ar another ST90 coil. JC Whitney has a 6 Volt generic coil that works, and the 6 Volt Volkwagen Beetle coil works - but mounting it is tough to do.
The spark plug wires tend to erode up inside the wire where the plug boot threads on. Remove boot, trim the spark plug wire back unitl fresh metal wire shows, and thread the boot on. You can get a spark plug wire splicer kit if the spark plug wire is too far gone, since the wire is embedded in the ignition coil.
The spark plug boots fail OFTEN. Many had a resistor inside that burns out. Replace with a non-resistor boot only if you use no electronics near the bike.
As mentioned, the spark plug is problematic. I have seen more spark plugs for these engines defective right out of the box, than any other plug. Its the narrow construction perhaps.
If you think the grounds are bad, you can use jumper leads to connect the battery ground wire to the coil mount and cylinder head for a test.
The ignition switches sometimes fail, or develop resistance and resulting Voltage drop issues.
Hope something in here helps.
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I did not see if you mentioned if it had electric start or not, but if you are only going to use the kickstart, you can use an NiMH RC pack made with sub-C batteries (not your typical RC battery pack which uses AA sized batteries, I am pretty sure Radio Shack carries them) at either 6.0 V or 7.2V in place of the lead-acid battery. I ran across someone who posted or has a website about his experience using a battery pack when I was looking for battery options for my 6 Volt C70 Passport. BUT if the ST90 has electric start, it will pull more amps than the battery pack can safely handle, so do not use it while using a battery pack.
Edit: Here is the article in Word format. I thought it was a website, instead it is a Yahoo Group, which you would have to join to see the file. Sorry.
http://f1.grp.yahoofs.com/v1/TPcAUk...JAMdT64BHA/6volt_NICAD_Battery_Conversion.doc
Paul
Edit: Here is the article in Word format. I thought it was a website, instead it is a Yahoo Group, which you would have to join to see the file. Sorry.
http://f1.grp.yahoofs.com/v1/TPcAUk...JAMdT64BHA/6volt_NICAD_Battery_Conversion.doc
Paul
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I do have a new, fully charged battery and it has 6.3 VDC when charged fully. The spark plug is also new but I felt it might be defective so I bought another plug with no luck. When I have the black/white wire unplugged from the coil with the switch on, I read battery voltage there. When I plug it into the coil the battery voltage completely disappears. Also, I do NOT have battery voltage to the points at any time while cranking the motor over. I have gapped the points to .012" and cleaned them. The timing looks like it may be a bit retarded but not enough to cause a no spark. I have tried grounding the coil to the engine block but still nothing. I suppose the spark plug wire could be defective but I still have no power to the points. This seems simple and would appear that the coil and/or condenser would be defective but I have tried two coils and 2 condensers. I am trying to pinpoint the exact problem before i buy more parts. I don't mind buying new points, coil, and condenser if they are really defective but I don't want to throw money away either.
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I'd disconnect black and ground wires from condensor and black from points, then check black wire for a ground. You shouldn't have one.
If you are not grounded, attach the lead for the points temporarily to ground and see if you can now read a short to ground. (You should) This checks continuity of the black wire from condensor to points.
I'm wondering if you are not achieving a ground for your coil to get the spark through the condensor. If wiring is intact, it could be a recessed pin in the engine disconnect connector.
If you are not grounded, attach the lead for the points temporarily to ground and see if you can now read a short to ground. (You should) This checks continuity of the black wire from condensor to points.
I'm wondering if you are not achieving a ground for your coil to get the spark through the condensor. If wiring is intact, it could be a recessed pin in the engine disconnect connector.