Jumping timing mark during test

[chelminski]

During the ignition test, the timing mark moves and does not stay in one position. This is not caused by the changing ignition angle because I uploaded a flat curve of 12 degrees and I am doing the test at 1500 RPM. The RPM is held very steadily. I decided to write to you for help. Maybe you have some ideas. I've already spent about 100 hours on this problem and I can't figure out if the fault is my mistake or if there's something wrong with the electronics. I kindly ask you to watch the video I have posted in the link below.

Dropbox

www.dropbox.com

The engine is a SeaDoo 951 ported with a CDI from IgniPower. The original wiring harness was completely removed and a new one was installed from scratch. From the SeaDoo GTX, I removed the MPEM and installed the ignition system like in a stand-up model. I believe I did this very carefully and consciously.

I sent the IgniPower back to Wolfgang Luger for testing, and on the test bench, the system seems to work correctly.

Of course, the jetski starts every time immediately, accelerates, and runs fine. Three years ago, I rebuilt this jetski from scratch, mostly with new original parts.

Maybe screenshots from the oscilloscope will be helpful to someone. Interestingly, the intervals between the sparks are not equal, and I don't know why. Sometimes the IgniPower reacts to the falling edge, and sometimes it is triggered by the rising edge. I haven't found any pattern in this behavior. Regarding the time interval between the sparks - the inconsistencies are in the range of 7-9%, so this should cause the timing mark to slightly fluctuate, but not jump as it does in my case.

Teal (blue) - Spark signal
Yellow - Tachometer
Purple - CPS



RRP billet aluminum electric box enclosure, SJ700 coil rebuild by Jetski Solutions, stock relay, IgniPower CDI. Flywheel with 4 teeth. Unfortunately, to use the Zeeltronic CDI, I need a flywheel with two teeth (from an older model). However, to replace it in this jetski, I need to remove the exhaust, then the carburetors, and then the engine, disconnecting the pump beforehand. Otherwise, there's no access to it.

 

[WFO Speedracer]

Actually you can just pull the pipe then shove something under the engine to support it while you remove the front engine mount, flywheel cover and the flywheel, do it many a time here.

The problem with asking this here is there are only a couple of guys here that know Seadoos and maybe a couple that have messed with that ignition and you are probably the only one that has done both.

 

[chelminski]

In fact, it's an interesting idea. The only downside is the exhaust gasket replacement.
@WFO Speedracer do you happen to know the exact part number for the flywheel for the SD951 with two teeth? I know what the differences were. All models from and including 1999 had four teeth already. I just wish I could confirm the part number. I assume the charging coil and trigger are the same.

Regarding my case - do you have any idea where such fluctuations could come from? Does it immediately seem like a CDI problem to you? Have you encountered EMC interference issues affecting CDI operation?

 

[WFO Speedracer]

I think all the stators and triggers are the same on Carbed 951'S , pretty sure you are looking for a 98 flywheel as it had the single coil part # 290886598 , in 99 they went to dual coils and the part number on the flywheel changed to #290887945 and it stayed that part # till 2002 when the ceased production on the 951.

 

[chelminski]

Thank you very much for your comment. Yesterday, I bought a wheel with exactly those numbers (290886598).
If someone could comment on the shifting timing mark, I would be grateful.

 

[Harbor]

When I use a timing light on my skis, 2 stoke Yamaha engines, I notice the timing bouncing around all over the place, which I thought was odd. I expected a steady timing reading.

I could see the timing hit the number I was expecting then bounce 20 to 79 degrees either side of the expected number constantly. I also noted the RPM was not changing with the bouncing timing, so it was an anomaly. If the timing was actually changing then the RPM would change as the timing changes.

I call it phantom timing and normal and I disregard it as the ski’s have no related symptoms and run normally,