Unconventional DIY ignition setup on 787

[Rconce01]

Hello,

I found this forum recently and I saw some folks here have ran the seadoo engines on the Zelltronics CDI and I figured some of you may be able to help me. I have an old 97 GSX and I had a very erratic timing issue and it turned out to be the MPEM. I did a pretty cheap setup with a low cost aftermarket CDI unit. I got the ski to run off the trailer and in the water which is great. Currently my problem is the idle is very unstable in the water and the engine is unstable hesitant up to midrange rpm. At high rpms 4k above it absolutely flies. Since the CDI unit is not programable i'm thinking the static angle timing is off. I read on some threads it's about 41 degrees on the 787. I noticed my line on the mag cup starts to trigger the pickup coil when the piston is at TDC. Do you think if I redrill the 6 holes with a 41 degrees advance I can solve the timing issue at idle to midrange?

I can post pics of my setup.

 

[bkspeedwerks]

@beerdart

 

[beerdart]

787 with Zeel static is 47 deg +/- 3

 

[Rconce01]

Thanks for confirming that's what I read on another thread. So I have two lobes on the mag should I set it to 47 degrees based on the start of the lobe or the end of the lobe?

The carbs were just rebuilt and it's not running lean. If I slightly choke it it dies faster so definitely getting fuel.

Attached is the timing chart and there are some dip switches with minimal instructions. Right now the leading edge of the lobe hits the trigger as the mag piston is at TDC. So im prob running way retarded by at least 40 degrees at idle.

 

[Jcary85]

Why don’t you hook a timing light up and check? That’s the only way you’ll know. Also, that curve kinda sucks. You probably want more timing down low then taper off after 5k ish to build heat in the pipe.

 

[Rconce01]

Why don’t you hook a timing light up and check? That’s the only way you’ll know. Also, that curve kinda sucks. You probably want more timing down low then taper off after 5k ish to build heat in the pipe.

I will go buy one and see what I got. Its a 20 dollar CDI and it's a simple build for my sister to cruise around so I wasn't looking for high end performance. When I hook up the timing light I'm supposed to get. 47 degree advance relative to the TDC mark of mag piston?

 

[Jcary85]

I will go buy one and see what I got. It’s a 20 dollar CDI and it's a simple build for my sister to cruise around so I wasn't looking for high end performance. When I hook up the timing light I'm supposed to get. 47 degree advance relative to the TDC mark of mag piston?

No you should get 20 after 3k rpm based on that curve. The static angle tells the ignition where the pickup is relative to TDC. Make a pointer at the coupler or flywheel and mark when piston is at TDC. Calculate distance for 5 degrees of rotation and mark flywheel or coupler every 5cDegrees. Run motor and set timing light at no offset. Rev motor up and mark should line up to 20 degree mark.

 

[Rconce01]

No you should get 20 after 3k rpm based on that curve. The static angle tells the ignition where the pickup is relative to TDC. Make a pointer at the coupler or flywheel and mark when piston is at TDC. Calculate distance for 5 degrees of rotation and mark flywheel or coupler every 5cDegrees. Run motor and set timing light at no offset. Rev motor up and mark should line up to 20 degree mark.

Gotcha I understand but right now my static angle is 0 not 47. Technically my trigger lobe needs to be hitting the pickup coil 47 degrees before the piston reaches TDC. Therefore the light will flash 47 degrees retarded under 3k once it gets up to 3k it will flash only 17 retarded. Am I not understanding correctly. Eventually when I redrill my mag cup the lobe needs to hit the trigger 47 degrees before the piston hits TDC for the timing to be "correct" at that point I'll get a 20 degree advance based in the curve and the engine should run right?

 

[beerdart]

Gotcha I understand but right now my static angle is 0 not 47. Technically my trigger lobe needs to be hitting the pickup coil 47 degrees before the piston reaches TDC. Therefore the light will flash 47 degrees retarded under 3k once it gets up to 3k it will flash only 17 retarded. Am I not understanding correctly. Eventually when I redrill my mag cup the lobe needs to hit the trigger 47 degrees before the piston hits TDC for the timing to be "correct" at that point I'll get a 20 degree advance based in the curve and the engine should run right?

47 degrees is the position on the pickup in relation to TDC it is a fixed location. The static angle is adjusted via the MPEM/CDI/Zeel as a reference.

 

[Rconce01]

47 degrees is the position on the pickup in relation to TDC it is a fixed location. The static angle is adjusted via the MPEM/CDI/Zeel as a reference.

Understood therefore 47 degrees before the piston hits TDC the lobe of the magnet needs to be hitting the trigger coil. Basically my CDI has no adjustment so I'm trying to vary the timing by altering it's physical position in the flywheel.

 

[Jcary85]

What ignition is it? Is it pre-configured for a specific static pickup angle? If so, you need to know that and need to set your pickup at that angle. This all sounds like way more hassle than its worth IMHO.

 

[OCD Solutions]

My thoughts exactly. There are countless reviews of the cheap CDI's and stators being absolute junk so your issues could all stem from a cheaply built unit that just isn't up to the task. I wouldn't make any timing mods without first verifying the actual timing. Pretty sure if you were off by 40deg, it wouldn't run at all.

 

[mikidymac]

5% of the time the cheap aftermarket Seadoo MPEM's work every time.
They are all junk so there is your issue.

 

[WFO Speedracer]

99% of the time when I get Seadoos in that customers have worked and used cheap Amazon-Ebay parts on those parts are defective. the same goes with ATV's,

I worked on a Yamaha 400 a few years back that had electrical issues , would not start and the Neutral light wouldn't come on, he had replaced the ignition switch and the starter solenoid with cheap Amazon parts, I replaced the parts with OEM parts and it is still running to this very day.

 

[Rconce01]

I appreciate the feedback but I know these little aftermarket CDI units are not great quality but I'm working with what I can afford. I set the TDC and the pointer every 1/4" is 5 degrees and this is the timing at idle up to 3k after that the timing gun doesn't flash but the engine still runs. Might be running too advanced? What timing do you typically get on a stroke idle to 3k ?

 

[Jcary85]

can’t really tell what’s going on in that picture. Was it supposed to be a video? What is the pointer?

 

[mikidymac]

The 787's don't really have static timing adjustment, everything is bolted in place. If the woodruff key isn't sheared it should not change.
For all the time you are wasting you could have pulled the MAG cover and checked the magneto cup and pickup.
Timing does not change between 3000 and 4000 rpm per the manual and the test procedure is in the manual. Timing mark should be 3.38mm BTDC at 3,500 rpm, you are not measuring degrees like on a car.

It';s the aftermarket MPEM.

 

[Rconce01]

can’t really tell what’s going on in that picture. Was it supposed to be a video? What is the pointer?

The pointer in the vertical threaded rod that's supported with the nut that's on the central hole the motor mount bracket has. Yes it's a screenshot of a video timing is at 37 degrees advanced at those rpms.

 

[Rconce01]

The 787's don't really have static timing adjustment, everything is bolted in place. If the woodruff key isn't sheared it should not change.
For all the time you are wasting you could have pulled the MAG cover and checked the magneto cup and pickup.
Timing does not change between 3000 and 4000 rpm per the manual and the test procedure is in the manual. Timing mark should be 3.38mm BTDC at 3,500 rpm, you are not measuring degrees like on a car.

It';s the aftermarket MPEM.

One of the first things I was did pull the front mag cover and I also pulled the flywheel and the mag cup pickup coil and key are good. I also made sure the timing plate was properly set.

Thanks I didn't know it was 3.38mm right now I converted my 1/4" marks and its 44 mm BTDC.

Here is the video. You can hear it's firing evenly. It just stutters in the water at idle all the way to midrange rpms.

 

[Jcary85]

The pointer in the vertical threaded rod that's supported with the nut that's on the central hole the motor mount bracket has. Yes it's a screenshot of a video timing is at 37 degrees advanced at those rpms.

Ok, so assuming your marks are correct and your light isn’t set for any advance and your TDC mark was accurate, your pickup would need to move 17 degrees. Should move so it’s triggered 17 degrees later. This tells me your ignition expects a static angle of 64. Did I math that correctly? I think someone said the factory static angle on 788 is 47, right?

Actually, looks like your curve doesn’t hit full timing advance until 3k. The fact you see the same timing from idle on up is fishy. You need to see what the mark is at after 3k