Yamaha P125a what are these wires

[paulwatkins]

p125a.jpg

hi I'm not getting any spark on this old motor, could it be these wires that are hanging I don't know what they are for any help please..there is a red a black and a stripped white

[pstephens46]

May need a few more pic, diff angles.

[boscoe99]

That is an oldy buy goody. Looks to be air cooled. From the 1970's I believe. I had a Sears **** Fisherman air cooled motor in the 70's. Worst motor I ever owned. A real POS.

Red should be for 12 volts positive battery power and black should be the ground.

With the motor running do you see voltage on the red and black wires? But if you got no spark I suspect you got no engine running.

I can't see the stripped white. Need to know the colour of the strip.

That motor has points I believe. Check the points.

[cpostis]

FYI, Check the link for some info on this motor. ***, it is an "Oldy" like Boscoe says!Yamaha P125A Page: 1 - iboats Boating Forums | 141297

[paulwatkins]

I will take some more picx in the morning I checked points all seem ok but will check again and take pics thank you and that is the same engine as posted in the link given thank you

[pstephens46]

That is an oldy buy goody. Looks to be air cooled. From the 1970's I believe. I had a Sears **** Fisherman air cooled motor in the 70's. Worst motor I ever owned. A real POS.

Red should be for 12 volts positive battery power and black should be the ground.

With the motor running do you see voltage on the red and black wires? But if you got no spark I suspect you got no engine running.

I can't see the stripped white. Need to know the colour of the strip.

That motor has points I believe. Check the points.

Is this motor electric start?

[paulwatkins]

no its pull start

[kieronr1]

P125a

Hi! Paul,
I have recently rebuilt one of these motors. Initially it was very difficult to start but after a total carb strip down and cleaning she fired up. The wires hanging in your photo are most likely coming from the lighting coil and you don't need to do anything with them unless you want to hook up a rectifier/regulator for charging etc. Do strip & clean your fuel pump also. Ensure that the wires coming from the stop switch on the tiller handle are not shorted or no hope of a start.
I have a full parts list and a lot of spare parts (all brand new) if you need anything. I am an outboard technician and will lend as much assistance as possible with your project. These are actually a 7.5hp 2 stroke air cooled motor and were mainly sold in Asia especially Bangladesh believe it or not. They are generally classified as 8hp and require a 40:1 fuel/oil mixture.

[pstephens46]

Makes sense now with the wires and being a pull start. Those things could probably run forever. How does it get enough cooling air with cowling on?

[paulwatkins]

Hi! Paul,
I have recently rebuilt one of these motors. Initially it was very difficult to start but after a total carb strip down and cleaning she fired up. The wires hanging in your photo are most likely coming from the lighting coil and you don't need to do anything with them unless you want to hook up a rectifier/regulator for charging etc. Do strip & clean your fuel pump also. Ensure that the wires coming from the stop switch on the tiller handle are not shorted or no hope of a start.
I have a full parts list and a lot of spare parts (all brand new) if you need anything. I am an outboard technician and will lend as much assistance as possible with your project. These are actually a 7.5hp 2 stroke air cooled motor and were mainly sold in Asia especially Bangladesh believe it or not. They are generally classified as 8hp and require a 40:1 fuel/oil mixture.

Hi Keiron1 thanks for your reply
a.jpg
here is my stop switch which seems not to be connected to anything

[paulwatkins]

b.jpg

here are some more photos this one is of the wires hanging

[paulwatkins]

d.jpg

this is what I got inside now the flat head screw at about 8pm on the picture is badly worn its attached to a spring contact switch or something, if this screw is loosened the contact switch rotates slightly. has this anything to do with a spark manythanks.p.s ive cleaned all the contacts still no spark

[TownsendsFJR1300]

[ATTACH]2603[/ATTACH]

this is what I got inside now the flat head screw at about 8pm on the picture is badly worn its attached to a spring contact switch or something, if this screw is loosened the contact switch rotates slightly. has this anything to do with a spark manythanks.p.s ive cleaned all the contacts still no spark

Your points don't appear to even be touching the "cam". That stripped head screw should be the lock down for the points. IE, your points don't look like they would even open... That spring (it really hard to see), may very well be the return spring to close the points..
It may also be the actual connector to the condenser as i don't see a separate wire for that.

Check the actual point contact surface for any arcing, etc. If no points are available, you can often use a cardboard nail file to clean up the surfaces...

In GENERAL, point opening is anywhere from .020" to .030" if you don't have the spec's for it

[kieronr1]

Yamaha P125A

I will be going to my workshop today. I will photograph and post all of the electrical connections on a working P125A. I can't remember the colour codes specific but will make sure to take detailed photos. This should clarify the situation.

[kieronr1]

Wire colours & use in P125A

There are 3 wires coming from underneath the Magneto. Colours are Red, Black & White. The White & Black go to the stop switch. You will note that the Black connector is a double lug. A connection can be taken from this and used with the Red to feed a voltage rectifier/regulator if you wish to charge a battery etc. Max current is 5A. If the Black & White wires are not connected to the stop switch this will not prevent the engine from starting but your options for stopping the engine are limited to cutting off the fuel supply & waiting for the carb to empty, disconnect the spark plug lead & run the risk of a nasty shock & possibly damaging the ignition coil or flooding the engine via the choke making it difficult to start again. However if the Black & White wires are connected to the stop switch & the stop switch is shorted via stuck contacts then you can not start the engine.
Also in a no spark scenario start at the very beginning. In order to generate current for the ignition coil primary side we need two things. A healthy Magneto with strong magnetism and a coil. When magnetos are left idle for years on end the magnets loose there magnetism or it gets so weak its unable to function properly. A quick test is to take some soft iron thats attracted to magnets and see if its pulled strongly to the magnets on the magneto. It should be difficult to pull away. If not the magnets themselves either need to be replaced or zapped back to life. ( different topic altogether ).
Next check the magneto coil for continuity. A multimeter with a low ohms scale is ideal for this purpose. A reading of around 15 to 25 Ohms is average for these coils.
After that your down to contact breakers or points as their well known. The rotating cam causes them to open and close. When the cam reaches its top lobe point the breakers should be open. As it passes they close. Without this happening the ignition coil will not function. A quick and easy check for this is to make up a small, say 6V light bulb and battery wired through the contact breakers. If they are working the light goes on and off. Permanently closed light stays on, permanently open no light at all. The gap between the contact breakers when there open and the time they take to close is related to whats known as the dwell angle but for these type of engines thats not overly critical. Rule of thumb in the old days we used a piece of cardboard from a cigarette packet to set them.
Doctors differ, patients live or die.
Assuming all above is ok and there is still no spark then the ignition coil is suspect or the HT lead going to the plug cap is damaged. Again a simple continuity test will answer that question.
Tried to post some photos but having no luck at the moment. Anyway feel free to PM me if more tech info needed.