Redbarron%%
Chief Petty Officer
- Joined
- Dec 7, 2017
- Messages
- 479
OK Settle in for a read.
When I first got my Hobie Sport Jet 90 hp Force I had problems setting it up getting the timing at idle and WOT right and the throttle and WOT on the carbs correct.
I started with the stock CDI system (really the whole engine stock) and had numerous problems, I wanted the "Added Reliability of the newer CDM system so I bought a three cylinder harness and the CDM modules and following another's lead I used the original trigger, grounding the white/black wire.
I could not get the 30 Degree and 9 degree settings and still get WOT on the carbs and the book position or even close with the idle set screw.
Flash forward and I found that the system REALLY NEEDS BIAS voltage so I copied the CDM setup from the late trigger.
This got the timing retarded where it was close and the 30 degree and 9 degree correct and amazingly the idle timing screw is very close to the settings called out in the book, BUT it was hard to start. I noticed that the timing light did not flash on the first turn or later, but eventually it would fire. It started easily if I grounded the White/black wire when starting.
So I decided to try installing a 12 volt relay that is connected to the +12 volt solenoid coil that id powered from the start switch on the ignition.
Vroom started first turn immediately on the very first start in the morning. The timing, if the white/black were left grounded was very advanced due to the lack of bias voltage, but this is just at initial starting. This seems to work like a boost similar to that on aircraft magnetos.
While I am using the CDM modules and a copied bias circuit that is probably not fine tuned for the CDI trigger coils as the bias circuit is built in the switchbox for the CDI.
However there could be a problem in my CDI switch box in the bias circuit that made starting hard and also caused the timing difficulties.
So if you are having a problem starting, verify that the ignition will flash the timing light on the first turn and consider adding the start boost relay after careful thought.
The relay is connected from the yellow/red wire that pulls in the starter solenoid and it's other coil connection goes to ground. One of the SPST contact terminals also goes to this ground, The other contact is tied to the White/black trigger wire as it connects to the bias circuit in the switchbox. Normally a negative voltage is present when the engine is running and it is rectified from the AC voltage generated by the trigger coils and is used to charge a capacitor. It's purpose is to offset the higher voltage rise as the rpm increases and caused the CDI SCRs to fire more advanced compared to the flywheel.
I cannot guarantee the accuracy of the above on your particular engine and I am still early in fine tuning the bias circuit for the old style trigger and flywheel to work with the new CDM modules.
If you are having trouble starting try momentarily grounding the white/black trigger wire just long enough to start, After the engine is running the timing will be too far advanced so do not leave it grounded.
When I first got my Hobie Sport Jet 90 hp Force I had problems setting it up getting the timing at idle and WOT right and the throttle and WOT on the carbs correct.
I started with the stock CDI system (really the whole engine stock) and had numerous problems, I wanted the "Added Reliability of the newer CDM system so I bought a three cylinder harness and the CDM modules and following another's lead I used the original trigger, grounding the white/black wire.
I could not get the 30 Degree and 9 degree settings and still get WOT on the carbs and the book position or even close with the idle set screw.
Flash forward and I found that the system REALLY NEEDS BIAS voltage so I copied the CDM setup from the late trigger.
This got the timing retarded where it was close and the 30 degree and 9 degree correct and amazingly the idle timing screw is very close to the settings called out in the book, BUT it was hard to start. I noticed that the timing light did not flash on the first turn or later, but eventually it would fire. It started easily if I grounded the White/black wire when starting.
So I decided to try installing a 12 volt relay that is connected to the +12 volt solenoid coil that id powered from the start switch on the ignition.
Vroom started first turn immediately on the very first start in the morning. The timing, if the white/black were left grounded was very advanced due to the lack of bias voltage, but this is just at initial starting. This seems to work like a boost similar to that on aircraft magnetos.
While I am using the CDM modules and a copied bias circuit that is probably not fine tuned for the CDI trigger coils as the bias circuit is built in the switchbox for the CDI.
However there could be a problem in my CDI switch box in the bias circuit that made starting hard and also caused the timing difficulties.
So if you are having a problem starting, verify that the ignition will flash the timing light on the first turn and consider adding the start boost relay after careful thought.
The relay is connected from the yellow/red wire that pulls in the starter solenoid and it's other coil connection goes to ground. One of the SPST contact terminals also goes to this ground, The other contact is tied to the White/black trigger wire as it connects to the bias circuit in the switchbox. Normally a negative voltage is present when the engine is running and it is rectified from the AC voltage generated by the trigger coils and is used to charge a capacitor. It's purpose is to offset the higher voltage rise as the rpm increases and caused the CDI SCRs to fire more advanced compared to the flywheel.
I cannot guarantee the accuracy of the above on your particular engine and I am still early in fine tuning the bias circuit for the old style trigger and flywheel to work with the new CDM modules.
If you are having trouble starting try momentarily grounding the white/black trigger wire just long enough to start, After the engine is running the timing will be too far advanced so do not leave it grounded.