Ignition/spark ST50

Good morning members,

Can someone head me in the right direction, I have managed to find a Honda st 50 approx 1972 in a garage clearance and I loved it as soon as I seen it so do my twin boys aged 3.

Problem appears to be no spark so I will mention what I have done then all comments will be great fully taken.

New spark plug and spark plug cap, new battery but I got no ignition light on dash (does this make a difference)?

So where do I start guys.

Regards Matt

Check
- ignition timing
- condensor
- set up points correctly
- earthing of the coil
- all wiring
- ignition switch
(battery has nothing to do with the ignition)
Good luck!

The green lamp on the speedo is for the neutral position on the gears
Silly question but have you looked at some of the earlier posting regarding this issue as I am sure it has come up before
Regards Tufty
P.S welcome to the forum

Thank you for your welcome and response guys.

Will make a start checking through that list so cheers for that waynus.

Tufty will take a look at previous post and see what other input has been suggested thanks!

Thanks once again guys.

Waynus wrote:Check
- ignition timing
- condensor
- set up points correctly
- earthing of the coil
- all wiring
- ignition switch
(battery has nothing to do with the ignition)
Good luck!

I am having the same problem ,I have fitted new points and condenser , set the timing , new spark plug and cap .Is there anyway to test the coil and the stator/generator

Here's what I would do, hopefully it will help,

Make sure your battery is ok, your timing is correct so the points open when they are meant to
Also make sure the points are gapped correctly.
I'm assuming the rest of your wiring loom and earths are in good order and your ignition switch is working.

Get yourself a new spark plug, yes a new one, rule this out as I've seen new plugs that are faulty.
Pull the coil lead off the plug and connect it to the new spark plug.
With the new spark plug out of the engine hold the white part of the plug against the cylinder head and crank the engine.
Make sure you turn on the ignition and you do not touch the end of the plug when you do this!
No spark? Let's check the generator then as this is easier than checking the coil due to it's location,,,,

Get yourself a bulb with two wires attached with crocodile clips at the ends.
Locate the Black ignition wire from the generator that connects to the coil, disconnect it and connect it to one of the wires from the bulb. Connect the other wire from the bulb to a good earth.
Crank the engine, if the generator is ok you should see the bulb flash intermittently.
If the bulb stays on check the points and or replace the condenser.
If you don't get anything then you need to look further at the generator.

If your bulb flashed intermittently then it looks secondary coil related, to check this you need two wires with crocodile clips on each end. Connect one wire to the negative of the battery and the other to the ground point on the coil.
Connect the other wire to the positive terminal on the battery.
Hold the spark plug to the engine and brush the end of the positive test wire against the positive terminal of the coil.
No spark, then replace the coil.

This should hopefully help you localise the problem.

There's one last bit I'd check too, but as I'm no auto electrician I'm not sure if this is the case on 6v ST70's so if someone can confirm this I'd be grateful. Check the neutral light switch on the engine, I know on another bike I owned this went faulty, as the bike thought it was not in neutral if would not start. Hopefully someone can confirm this

Good luck, Let us know how you get on,

Best,

Blue

Good post Blue!

- no battery is needed for a correct working ignition system
- only bikes with a side stand or neutral safe switch can have the problem you're talking about

Waynus wrote:Good post Blue!

- no battery is needed for a correct working ignition system
- only bikes with a side stand or neutral safe switch can have the problem you're talking about

Thanks Waynus,

I'm learning and quite happy with electrics now.
Next step is a engine build, got myself z50 12v bottom end, honda 4 speed gearbox, honda manual clutch and cover, Tbolt 88cc barrel and piston, and an OT E22 head, just need to clear some space so I can put it together.
Still working on my Lady which I have to finish 1st as it's been far to long and I've had enough of the jokes about how long it's taking

Once you built your first engine, you'll be addicted!
Lego for adults (or someone in that age range)!

Blue wrote:Here's what I would do, hopefully it will help,

Make sure your battery is ok, your timing is correct so the points open when they are meant to
Also make sure the points are gapped correctly.
I'm assuming the rest of your wiring loom and earths are in good order and your ignition switch is working.

Get yourself a new spark plug, yes a new one, rule this out as I've seen new plugs that are faulty.
Pull the coil lead off the plug and connect it to the new spark plug.
With the new spark plug out of the engine hold the white part of the plug against the cylinder head and crank the engine.
Make sure you turn on the ignition and you do not touch the end of the plug when you do this!
No spark? Let's check the generator then as this is easier than checking the coil due to it's location,,,,

Get yourself a bulb with two wires attached with crocodile clips at the ends.
Locate the Black ignition wire from the generator that connects to the coil, disconnect it and connect it to one of the wires from the bulb. Connect the other wire from the bulb to a good earth.
Crank the engine, if the generator is ok you should see the bulb flash intermittently.
If the bulb stays on check the points and or replace the condenser.
If you don't get anything then you need to look further at the generator.

If your bulb flashed intermittently then it looks secondary coil related, to check this you need two wires with crocodile clips on each end. Connect one wire to the negative of the battery and the other to the ground point on the coil.
Connect the other wire to the positive terminal on the battery.
Hold the spark plug to the engine and brush the end of the positive test wire against the positive terminal of the coil.
No spark, then replace the coil.

This should hopefully help you localise the problem.

There's one last bit I'd check too, but as I'm no auto electrician I'm not sure if this is the case on 6v ST70's so if someone can confirm this I'd be grateful. Check the neutral light switch on the engine, I know on another bike I owned this went faulty, as the bike thought it was not in neutral if would not start. Hopefully someone can confirm this

Good luck, Let us know how you get on,

Best,

Blue

Hi Guys ,

Well due to work and holidays I have just managed to get back to the Dax , Well I checked all of the above and fitted a new coil checked the Earths and did the check on the Generator and it all checked out ok ,But I still have no spark so what I did was check the neutral light bulb was ok it was but only using the battery to test it .It was not coming on with the battery connected up as normal with the ignition switched on and it was in the neutral position . So I then unclip the neutral wire and ground the wire and the light came on does this mean the neutral light switch is broken and could this be the problem