785 project - restoration work

[pascoea]

Thanks for the input gents. The more I was thinking about it, not having everything hooked up is probably not the best way to test. I'm going to get everything hooked up tonight and re-test.

I didn't test voltages on the other coils, as the resistance values were all within spec, but I'll give that a go as well. The prior owner didn't have any info on what electrical gremlins they were chasing down when they shelved it, so probably best to just check them all.

[K447]

That sounds low but I'm not 100% certain what it should be. How do the cranking voltages compare to the other windings in my thread? If the rest are all similar then I would assume the stator windings are too weak to create enough voltage.

If multiple stator coil voltages measure weak (and other factors such as slow engine cranking have been ruled out), sometimes the ring magnet inside the flywheel can become weakened. If you have another flywheel available you can compare the magnet strengths using a screwdriver tip, or just install the other flywheel and see if the results improve.

Stator windings can fail if the insulation between windings fails and effectively shorts those windings together. The insulation can fail if the winding wires rub against each other or against the armature structure with engine vibration. I would expect when this type of failure occurs it would affect one stator winding more than the others, as whichever winding fails first will prevent the engine from running, therefore no further vibration to further degrade the other windings.

[Myself]

That sounds low but I'm not 100% certain what it should be. How do the cranking voltages compare to the other windings in my thread? If the rest are all similar then I would assume the stator windings are too weak to create enough voltage.

[pascoea]

I don't ever condemn a stator on ohms alone UNLESS it's dead shorted to ground. Does it still produce a good AC voltage number while cranking? Around 20 VAC?
Maybe read through this thread..Troubleshooting Fuji 650 750 780 with no/intermittent spark - Greenhulk Personal Watercraft Performance Forums
I've been ALL OVER the Fuji electrical systems!

Hey Myself, read through your thread (the starter, really? Lol. Don't mean to laugh at your misery, but that sounded like a bear to chase down.) and tested the voltage on the pulser. It hits just north of 6vac while cranking. So the dumb question... how much of the CDI to I need to have hooked up to consider it a valid test? I connected the pulser, and a couple other random wires between the CDI and Stator, basically everything I could without involving the junction board. I have to assume that with the lower resistance, some of the windings are shorted together, and that's not letting the voltage get high enough. Maybe tomorrow I can get the rest of the jbox hooked up and give it a try again, I wouldn't think that would make a difference, but who knows.

If I wanted to get that coil re-wound do you have any recommendations on who I could send it to? I emailed a couple local motor shops, but they pretty much told me to kick rocks.

[xlint89]

Can I get some input on the stator? All of the readings are within the +/- 10% except the Pulser Coil. Supposed to be 90 (assuming the Pro stators are the same as the others) but it's testing at 22 ohms. Would that be enough difference for you guys to condemn the stator to a life of landfill duty?

I looked thru ebay for a replacement, but unsurprisingly came up empty. Any thoughts on where to source one? And I thought I had heard that the 750 or 780 stator/flywheel would be an acceptable alternative, is that accurate?

I agree with the previous replies. Keep it. Ohms can change due to ambient temp.

But to answer your Q, you can use a 1994-95 750 and any 780 magneto and flywheel as a replacement. (you cannot use a 785 flywheel with a 750 or 780 magneto. You need to use the matching magneto and flywheel)

[pascoea]

I don't ever condemn a stator on ohms alone UNLESS it's dead shorted to ground. Does it still produce a good AC voltage number while cranking? Around 20 VAC?
Maybe read through this thread..Troubleshooting Fuji 650 750 780 with no/intermittent spark - Greenhulk Personal Watercraft Performance Forums
I've been ALL OVER the Fuji electrical systems!

Thanks for the link. I'll take a look through that. (I tried going thru a similar link from the "Polaris knowledge" site, but they are all still busted since the GH update.)

I'll have to check the cranking voltage once I get this back together, the engine is still sitting naked on my bench. I assume I want the CDI hooked up when I do that test?

[pascoea]

Don't ever condemn a stator. They can be rewound and a ton of things if they aren't right. Though it's hard to find someone who will do it and it's usually easer to get a new one.

Hmm. That's an interesting idea. I poked around a bit, this is one of the wrapped coils, so it wouldn't be SUPER hard to re-do.

[sdlvx]

Don't ever condemn a stator. They can be rewound and a ton of things if they aren't right. Though it's hard to find someone who will do it and it's usually easer to get a new one.

[Myself]

I don't ever condemn a stator on ohms alone UNLESS it's dead shorted to ground. Does it still produce a good AC voltage number while cranking? Around 20 VAC?
Maybe read through this thread..Troubleshooting Fuji 650 750 780 with no/intermittent spark - Greenhulk Personal Watercraft Performance Forums
I've been ALL OVER the Fuji electrical systems!

[pascoea]

Can I get some input on the stator? All of the readings are within the +/- 10% except the Pulser Coil. Supposed to be 90 (assuming the Pro stators are the same as the others) but it's testing at 22 ohms. Would that be enough difference for you guys to condemn the stator to a life of landfill duty?

I looked thru ebay for a replacement, but unsurprisingly came up empty. Any thoughts on where to source one? And I thought I had heard that the 750 or 780 stator/flywheel would be an acceptable alternative, is that accurate?

[xlint89]

Absolutely. I wish everyone would do a leak down test after engine assembly. Would save a lot of headaches.

Many people replace pistons without figuring out why it failed. Then they fail again.

[pascoea]

Power valves are not an air tight seal. Remove them from the engine and blank off the opening. Then try the test.

Yeah, that's kind of what I figured, the whole "doesn't have a sealing mechanism" should have been a clue for me. I I'll give that a go, thank you.

What wear ring are you referring to? The collar on the tail end of the crankshaft? There's an O ring between the crank and the collar. Then you have the collar sealed with the main rear seals. What's leaking there?

That's the guy. I had forgot the o-ring on the prior test, so I think I've got that sorted. There wasn't a groove on the shaft where I was expecting, so I didn't think it needed the o-ring. And it had been so long since I disassembled I didn't remember taking one out of there. Live and learn, guess that's why we test.

[xlint89]

Power valves are not an air tight seal. Remove them from the engine and blank off the opening. Then try the test.

What wear ring are you referring to? The collar on the tail end of the crankshaft? There's an O ring between the crank and the collar. Then you have the collar sealed with the main rear seals. What's leaking there?

[pascoea]

I finally made some progress!
Engine is re-assembled, I did the leakdown test but it's failing because the power-valves and wear ring aren't sealing. I believe I have the wear ring figured out, need a new o-ring, but what the heck do I do with the power valves? There doesn't appear to be any sort of seal, besides the bellows. Would a dollop of grease on the shaft do the trick?

[pascoea]

Thanks for the reply. I ended up finding a washer at the local powersports place, as for the seats I had ordered from https://www.speedaddicts.com, they let me return and re-order the correct ones.

As far as the carb question, I believe I understand. Below the pump body makes sense, I'm using the rubber seal (hate to call it an o-ring) instead of the paper gasket. Above the pump body, I'm omitting the 2nd gasket because they substituted the o-ring on later 44s. I think it's the "Not used on BN 38" comment next to my red arrow that is really what's throwing me off. Seems like it should say "Not used on BN 38 and Late BN 44"