Unconventional DIY ignition setup on 787

[WFO Speedracer]

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

Pickups on these are fixed an no way in hell you are moving it 17 degrees and keeping it stable and in place, they broke pickup brackets as they were stock, the timing is adjusted with a hand held programmer and since he has rigged this there is now no way to adjust the timing except by continuing to rig stuff up, good luck going down this road , it's a bad road but it's yours to go down, I am just glad it's you and not me.

 

[Rconce01]

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

Awesome thanks yes I can confirm the mark on the PTO was set at TDC with a dial indicator at the mag piston. The timing gun was a cheap one and it wouldn't pulse at the higher rpms. I will try to get a better one.


I can redrill the holes in the mag cup 17 degrees back and that will set the trigger signal back. " like the 717 which allowed a mechanical adjustment of the timing" As far as the timing advance on this cdi I think I know why it's advancing it so much at idle. Since this CDI is for a single piston engine and the seadoo has dual mag lines 180 degrees apart when my engine is idling at 2,000 rpms the CDI multiplies it by 2 and thinks the motor is at 4k. That's prob why it's advancing it so much.

It has some dip switches for rpm limit and when I set it to 8k it stops reving at 4k. When I set it to 16k it stops at 8k.

 

[Sparkplug]

Perhaps get off xh20. Take those skills to a machine shop or tire shop. Tell them you will work for a day for 150 dollars. And get a proper cdi/controller. The amount of typing and time spent on this is crazy. I'm the cheapest guy in the world and I wouldn't want my sister stranded on the lake cause I bought a 20 dollar cdi and talked about it for 3 days online.

 

[Jcary85]

Perhaps get off xh20. Take those skills to a machine shop or tire shop. Tell them you will work for a day for 150 dollars. And get a proper cdi/controller. The amount of typing and time spent on this is crazy. I'm the cheapest guy in the world and I wouldn't want my sister stranded on the lake cause I bought a 20 dollar cdi and talked about it for 3 days online.

and this is why the forum is dead (posts like this). Guy is trying something different. cut him some slack and maybe give some advice. I agree, using something stock is way smarter but its a learning experience none the less.

 

[OCD Solutions]

A man who carries a cat by the tail learns something he can learn in no other way.

- Mark Twain


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[Sparkplug]

Encouraging a guy to waste time. Money. And risk his sister is why the forum is dead. They are all out on broken down jet skis in the middle of the lake searching for their sisters.

He's not doing anything new. He's wasting a whole bunch of his and others time. But hey. It's ours to waste.


The forum is dead. Cause jet skis aren't cool anymore man. The 90s was 30 yrs ago. Waverace was 28 yrs ago. It's such a niche hobby. Who's Wait 5-10 years and tc and high speed and all those guys. Will be doing turf on giant sit downs for their main line of business. Performance fun, is absolutely going the way of the


"They still make those?"

 

[Rconce01]

Guys I appreciate the insight I really enjoy tinkering and learning about these things. As far as safety we always ride in a group friends and family I would never just send anyone off alone into the ocean with an idea like this. I came here because I saw folks who contributed ideas and tried unconventional things and I do value people's time so it's not my intention to waste anyone's time. I love this old school 2 stroke niche and always wanted to create a simple CDI circuit that wouldn't cost hundreds of dollars for people to keep their skies running when an MPEM would go bad. I was inspired by others that did it in Yamahas like

And

I know it could be done and I know it works and I'm just trying to make it better.

No one enjoys paying $100 dollars for a dumb dess security key and an $500 MPEM that serves no purpose other than to send a cdi signal and provide 40 cables with of info of information to $300 digital gauge thats dead.

These old skis cost under 1k and solving an alternative solution to create a properly timed spark that costs under 50 bucks is worth trying. Spread the love it makes the world a better place.

 

[Jcary85]

Good stuff! If you are bored, go check out this thread https://www.x-h2o.com/threads/need-...ition-brain-design.206966/page-5#post-2133349 - I'm working on a speeduino based ECU for ignition only control. Not CDI, but uses "smart" coils that output CDI like spark energy and speed. Not as low cost as what you are looking to do, but might interest you.

 

[WFO Speedracer]

Good luck , those Chinese GY6 CDI boxes are usually not worth pissing on, you have taken a DC CDI system and installed an AC CDI ,if you are dead set on doing tis a Polaris DC conversion CDI box would probably be a much better option. RM Stator makes one. The one in the vid is for a four stroke but the make them for the 350-400 two strokers as well.

 

[Rconce01]

Good stuff! If you are bored, go check out this thread https://www.x-h2o.com/threads/need-...ition-brain-design.206966/page-5#post-2133349 - I'm working on a speeduino based ECU for ignition only control. Not CDI, but uses "smart" coils that output CDI like spark energy and speed. Not as low cost as what you are looking to do, but might interest you.

That's very cool! I took a look at the circuit and it's very complex way beyond my knowledge or basic circuits. I like the concept of reusing the start stop switch!

 

[Rconce01]

Good luck , those Chinese GY6 CDI boxes are usually not worth pissing on, you have taken a DC CDI system and installed an AC CDI ,if you are dead set on doing tis a Polaris DC conversion CDI box would probably be a much better option. RM Stator makes one. The one in the vid is for a four stroke but the make them for the 350-400 two strokers as well.

I installed a DC CDI not an AC one. My ski had a trigger coil for the DC setup so it was pretty easy wiring it in.

I will look at the Polaris DC conversion thanks!

 

[Rconce01]

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

I retarded the timing by 15 degrees by redrilling the mag cup. The idle is much better and the midrange too. High range is still insane. I'm going to redrill again and go back another 15 degrees and let you know if it keeps improving. Tomorrow I'll also have a new timing gun that hopefully works the entire rpm range and I'll make some new videos in the water. Typically the leading edge of the lobe lines up with the little hole in the flywheel.

 

[Rconce01]

Runs great decent idle good midrange and killer top end.

Thanks for all the help and insight.

 

[Jcary85]

So did you check it again with a different timing light? Keep us posted on long term reliability. Glad it’s running.

 

[Rconce01]

So did you check it again with a different timing light? Keep us posted on long term reliability. Glad it’s running.

I did even with the new timing light it shuts off after midrange rpm but at 3k and below I'm now at 20 degrees advanced.

I tried 15 degrees and it struggled to start. It would crank but not start. When it did run it didn't feel lively.

Anything beyond 20 would cause poor idle low end and mid range stall. It would cause like a shudder of the engine and it would clear out beyond 4k.

I will try other cheap DC CDI and see if it changes anything in the timing.

The ultimate test will be the reliability but one thing is for sure the factory MPEM makes a very weak spark and this setup creates a nice strong visible spark.

Hope all of you enjoy the weekend!

 

[G-Body]

Based on what I read it sounds like you are using one of the GY6 scooter AC CDI`s. They don`t have much of a curve to them and I don`t think I have found one yet that pulls timing on the top end which is what we should have for a 2 stroke jetski motor. That being said they will get you back running. My surfango Kayaks use them because they are GY6 powered. They also make programmable ignitions for the GY6 scooters, but I have not had luck with them. https://www.ebay.com/itm/273116074512?hash=item3f96fc9210:g:1isAAOSwc7RaMjpT&amdata=enc:AQAIAAAA4JeHVv0tsObr4uWXMbWRHjy96kpYCNcUaOk+MJEX6bmyn8Jme/to1Fwo57vPJTUddAEWnb8a7rE2+6D4f7KeDvJkOmVAQsXryFPLcEXb4xuRpmGkZ5SsJvEAiWMSAwmu5knJ9MhdByk4PD4pH+mmQv35yZtUIxrHvaoD99dfKLuHXKJ76RtK+rkRhKhzGVpSXGCIsvTUf7Sfz7eAcUZ//BTzPF6t5xBmKaVNR5kXYPyAl114bVbdz5nT6CJ8BMZ9jjltLSeCJEqisGvoLl0xd3xnBAC0z04DQa0AdAzpSqYc|tkp:Bk9SR-DA6s_PYg I bought 4 of these cause I had several motors that I wanted to switch to a programmable ignition. The first one let me idle the motor for about 15 minutes while i was checking it out, then stopped sparking. The next 2 I was never able to get a spark out of and the last one I don`t think it sparked more than 2 revolutions. Those CDI`s will think that they are running double the RPM that the motor is actually running as they are designed for the single cylinder gy6 motor which fires once per revolution (the gy6 is 4 stroke, but its a wasted spark design). The jet ski is 2 stroke wasted spark so it fires twice per revolution. So far the cheap GY6 CDI`s that I have used have been very reliable, with the exception of the programmable ones.

 

[WFO Speedracer]

Based on what I read it sounds like you are using one of the GY6 scooter AC CDI`s. They don`t have much of a curve to them and I don`t think I have found one yet that pulls timing on the top end which is what we should have for a 2 stroke jetski motor. That being said they will get you back running. My surfango Kayaks use them because they are GY6 powered. They also make programmable ignitions for the GY6 scooters, but I have not had luck with them. https://www.ebay.com/itm/273116074512?hash=item3f96fc9210:g:1isAAOSwc7RaMjpT&amdata=enc:AQAIAAAA4JeHVv0tsObr4uWXMbWRHjy96kpYCNcUaOk+MJEX6bmyn8Jme/to1Fwo57vPJTUddAEWnb8a7rE2+6D4f7KeDvJkOmVAQsXryFPLcEXb4xuRpmGkZ5SsJvEAiWMSAwmu5knJ9MhdByk4PD4pH+mmQv35yZtUIxrHvaoD99dfKLuHXKJ76RtK+rkRhKhzGVpSXGCIsvTUf7Sfz7eAcUZ//BTzPF6t5xBmKaVNR5kXYPyAl114bVbdz5nT6CJ8BMZ9jjltLSeCJEqisGvoLl0xd3xnBAC0z04DQa0AdAzpSqYc|tkp:Bk9SR-DA6s_PYg I bought 4 of these cause I had several motors that I wanted to switch to a programmable ignition. The first one let me idle the motor for about 15 minutes while i was checking it out, then stopped sparking. The next 2 I was never able to get a spark out of and the last one I don`t think it sparked more than 2 revolutions. Those CDI`s will think that they are running double the RPM that the motor is actually running as they are designed for the single cylinder gy6 motor which fires once per revolution (the gy6 is 4 stroke, but its a wasted spark design). The jet ski is 2 stroke wasted spark so it fires twice per revolution. So far the cheap GY6 CDI`s that I have used have been very reliable, with the exception of the programmable ones.

Thats why I suggested the RM stator Polaris CDI it should fire at the correct rate and pull back the timing at high RPM. My fear with that setup is that it will burn the exhaust side of the pistons slam off with that much timing and no way to retard it on top end

I usually run stock ignition or MSD total loss on my 787's . I do realize neither of those is a cheap option but I have a handheld programmer so I cvan make DESS keys and set timing on the stock setups.

 

[Rconce01]

Based on what I read it sounds like you are using one of the GY6 scooter AC CDI`s. They don`t have much of a curve to them and I don`t think I have found one yet that pulls timing on the top end which is what we should have for a 2 stroke jetski motor. That being said they will get you back running. My surfango Kayaks use them because they are GY6 powered. They also make programmable ignitions for the GY6 scooters, but I have not had luck with them. https://www.ebay.com/itm/273116074512?hash=item3f96fc9210:g:1isAAOSwc7RaMjpT&amdata=enc:AQAIAAAA4JeHVv0tsObr4uWXMbWRHjy96kpYCNcUaOk+MJEX6bmyn8Jme/to1Fwo57vPJTUddAEWnb8a7rE2+6D4f7KeDvJkOmVAQsXryFPLcEXb4xuRpmGkZ5SsJvEAiWMSAwmu5knJ9MhdByk4PD4pH+mmQv35yZtUIxrHvaoD99dfKLuHXKJ76RtK+rkRhKhzGVpSXGCIsvTUf7Sfz7eAcUZ//BTzPF6t5xBmKaVNR5kXYPyAl114bVbdz5nT6CJ8BMZ9jjltLSeCJEqisGvoLl0xd3xnBAC0z04DQa0AdAzpSqYc|tkp:Bk9SR-DA6s_PYg I bought 4 of these cause I had several motors that I wanted to switch to a programmable ignition. The first one let me idle the motor for about 15 minutes while i was checking it out, then stopped sparking. The next 2 I was never able to get a spark out of and the last one I don`t think it sparked more than 2 revolutions. Those CDI`s will think that they are running double the RPM that the motor is actually running as they are designed for the single cylinder gy6 motor which fires once per revolution (the gy6 is 4 stroke, but its a wasted spark design). The jet ski is 2 stroke wasted spark so it fires twice per revolution. So far the cheap GY6 CDI`s that I have used have been very reliable, with the exception of the programmable ones.

The one I'm using is not an AC Cdi it's a DC CDI. Yes I'm aware it thinks the motor is spinning twice as fast I noticed it when I set the dip switches to the different rev limiter values it stopped the motor at half the set value for the rpms. I really appreciate your insight again this is not meant to be "the best CDI" but it's intended to give someone with a bad MPEM an opportunity to run a seadoo without the proprietary electronics. We should call it SEADOO Open source ignition concepts! Proceed at your own risk. Side Effects include savings and fun in the water.

 

[Rconce01]

That's what I'm running for those that would like to know.