Anyone have a clue how this ever worked???

[pcmandevon]

This is a little long but worth reading….(I Think)

Okay, some of you may remember this boat I have been working on for a while. It’s a 96 Sportster that the last owner put a 787 in. When I first got this thing the owner side he bought a SBT 787 and put it in the boat but was never able to get the carbs tuned.
I corrected the issues with the carbs and the boat ran, badly, but it did run. When at WOT the boat would sputter and then take off like a rocket. Then about 45 seconds later it would die.

The more I started to tear into engine the more concerned I became about how this boat was even running in the first place. Here is a small list of what I found…

1.The engine was connected to an MPEM (278000510) from a 95 Sportster, this should run a 717.
2.The MPEM was somehow connected to a CDI. ???

I removed all the electrical from the boat and replaced it with a MPEM and rear electrical from a ski. Then I discovered that the plug was missing from the Stator housing and a bunch of wires were coming out instead.

3. I order a new (to me) housing that came with a working stator and pickup coil.

When I removed the stator housing from the engine, I found a stator from a 717 that someone had made an adapter plate for to mount to the front of a 787 housing. To my surprise the mag cup was missing the protrusions on each side, and the there was no pickup coil.

Long story short (too late) this engine did run at one point…anyone have an idea how??? I’m completely stumped, everyone I’ve talked to looks at me like I’m crazy.

Devon

 

[kustomkarl]

Devon, praise the lord, it's a miracle!!! Seriously, the electrical is a funny thing. If you have fuel ,air and spark and the timing is just right under compression, it will fire. I have heard stranger things than this before, and it runs for some strange reason.

Karl,

 

[Dr Honda]

Well... it's easy. You had a complete ignition from a 720 engine. The 720 doesn't use a pick-up coil. It uses a standard high voltage MAG-CDI system. The problem is... unless they used a flywheel from a 720... I don't know how they timed it. (witch is why it may not have run well)

 

[pcmandevon]

I thought it was basically using the 717 ignition too. However, the ignition built into the 717 stator was only hooked up to the MPEM, and then to the 787 CDI. I guess at this point it doesn’t matter. The damage has already been done; now I just have to fix it.

I engine is going to need a top end rebuild already, because I think the guy that put it in, damaged it. I’m having a friend do that right away. As part of this whole adventure I think I’ve decided to put the oil injection system back in place. The fuel tank already has 15 gallons of fresh 35:1 premix in it (for break-in), and I’m not too worried about fouling the plugs. So I’ll clean up the injectors, replace all the hose, and fill the oil tank up with new BRP synthetic oil. Hopefully that will be the last of the big money items for a little while. Wish me luck. Devon.

 

[pcmandevon]

Devon, praise the lord, it's a miracle!!!

Thank you Karl, that made me laugh. :lols: Devon

 

[kustomkarl]

Devon, just be sure the oil in the fuel and injector tank now is synthetic, because it the other guy used mineral it won't mix properly...Synthetic blend or synthetic will mix ok, but never with mineral.

Karl

 

[pcmandevon]

The injector tank and all the lines running from it are now empty, but the fuel tank has about 15 gallons of premix (Seadoo Mineral Oil).

Should I drain the fuel tank?

I would be going from BRP Mineral to BRP Synthetic.

Thank you again. Devon.

 

[kustomkarl]

The 2 oils won't mix properly. Either drain and add all the same oil, or keep running mineral.

Karl