Yamaha 5hp 2 stroke-weak spark

[C08]

This engine was used as a reserve engine before I bought it and I have never used it but ti ran fine 3 years ago. Done very little hours by the look under the cover.
No start and sparks are barely visible. So either no volts to drive the CDI unit or a dead CDI.
There are only two wires for the CDI, a live and earth wire. How can I check this with a meter?

 

[VicS]

See the CDI Electronics trouble shooting guide

https://www.cdielectronics.com/wp-content/uploads/2016/12/7th-Edition-Troubleshooting-Guide_RS.pdf

or the service manual to which a link was posted on here a few days ago ( Sorry I dont have the link .. I downloaded the manual!) **

You will need a "peak reading" meter, or a DVA adapter for an ordinary meter ( easily made if you can solder a few simple components together), for the procedures described in the CDI guide

Or the special equipment described in the Service manual

For a start perhaps check the coil resistances they might identify the problem

BUT you lost me at the point whre you said only two wires for the CDI unit ....



** http://www.johansilen.se/Manual1/Yamaha 4AC Service & Repair Manual.pdf

 

[Boathook]

This engine was used as a reserve engine before I bought it and I have never used it but ti ran fine 3 years ago. Done very little hours by the look under the cover.
No start and sparks are barely visible. So either no volts to drive the CDI unit or a dead CDI.
There are only two wires for the CDI, a live and earth wire. How can I check this with a meter?

The spark on my malta is difficult to see and is I belive a characteristic of the smaller yamaha's.

 

[VicS]

The spark on my malta is difficult to see and is I belive a characteristic of the smaller yamaha's.

The spark should jump a minimum of 8mm when tested with an adjustable gap spark tester

 

[DownWest]

See the CDI Electronics trouble shooting guide

https://www.cdielectronics.com/wp-content/uploads/2016/12/7th-Edition-Troubleshooting-Guide_RS.pdf

or the service manual to which a link was posted on here a few days ago ( Sorry I dont have the link .. I downloaded the manual!) **

You will need a "peak reading" meter, or a DVA adapter for an ordinary meter ( easily made if you can solder a few simple components together), for the procedures described in the CDI guide

Or the special equipment described in the Service manual

For a start perhaps check the coil resistances they might identify the problem

BUT you lost me at the point whre you said only two wires for the CDI unit ....

View attachment 121771

** http://www.johansilen.se/Manual1/Yamaha 4AC Service & Repair Manual.pdf

Thanks for that, got a Malta on the bench with no spark..

 

[C08]

D...oh. Because the ignition coil has CDI on it I assumed that was the CDI and the other plastic block was just a termination/connector box not the CDI. It gets expensive fault finding by substitution! Perhaps I am expecting to see a better spark than they generate, certainly barely visible and not across the spark gap with a new plug, just to earth with a tiny gap.

 

[VicS]

D...oh. Because the ignition coil has CDI on it I assumed that was the CDI and the other plastic block was just a termination/connector box not the CDI. It gets expensive fault finding by substitution! Perhaps I am expecting to see a better spark than they generate, certainly barely visible and not across the spark gap with a new plug, just to earth with a tiny gap.

If it wont jump 8 mm there something wrong

Time make a DVA adapter and get troubleshooting