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  1. #21
    Quote Originally Posted by sdlvx View Post
    The basic idea of how these ignition systems works is

    1. Flywheel spins around on the crankshaft
    2. Sensors on the flywheel are read by a stationary sensor on the crank case in the flywheel area
    3. When the sensor is tripped, it sends a signal to the CDI
    4. The CDI then has a brief delay (timing curve) based on RPMs before it sends the signal to the ignition coil
    5. The ignition coil sends the spark from the coil to the spark plug

    A regular Fuji fires all three ignition coils at the same time whenever the sensor is tripped. The flywheel must be aligned with the piston positions. If they're not, the signal for when to send the spark is wrong. I always thought it seemed like voodoo magic but once I understood how it works it's not that complex.
    Thank you for this explanation. It doesn't seem overly complicated after reading that! My next step is going to be putting spark testers on all the wires at once and also ohming out the leads for everything listed in the sticky thread about the 780's.


  2. #22
    Ok, I didn't have time to get individual testers for spark, but, I did work on it for 2 hours today and here are the results:

    Measured ohms on spark plug caps and realized there was an obvious issue there. Reinstalled caps and engine will now run on every cylinder by itself, PTO is still rough and sometimes cannot idle for longer than a few seconds. Ohms tests results as follows and my meter has a .2 offset.

    Red/Purple to Yellow= .7 ohms (.6 normal)
    Red/Purple or Yellow to Black= 0 ohms (infinite/open/no connection normal)
    White/Yellow to Black= 222.2 ohms (220 normal)
    Blue/Red to Red/White= 59.8 ohms (90 normal)
    Red/White to Black= 289.1 ohms (infinite/open/no connection normal)
    Red/White to Green/Red= 476.4 ohms (490 normal)

    I relocated battery negative ground wire from engine bed plate to PTO cylinder head bolt as noted from another post.

    Black Stator wire grounding check: .2 ohms (zero or very close to zero normal)

    All 3 ignition coils Black to Black/White= .4 ohms (.6 normal)

    After reinstalling spark plug caps, new reading for total resistance from cap through coils is: MAG=7.9k ohms, CEN=8.61k ohms, PTO=8.37 ohms (8k-9k normal)

    Ignition coils connected in series without connecting to CDI= .7 ohms (1.8 ohms normal)

    That's all I had time to test tonight. I also reinstalled a new small fuel filter (looks like it is in between tank and petcock) because I noticed a good amount of dark sediments inside of it. Let me know if these test results make any sense.

  3. #23
    Well, I couldn't figure it out. I ended up taking it to a mechanic that openly said he doesn't usually like to work on Polaris'. He couldn't figure it out either and his end guess was the cdi was bad. I found a used cdi and installed it last night, I didn't notice any change. I did find that the pink gas gauge wire had somehow been off. After reconnecting it, it now revs to about 5k. It was stuck at around 4200 before. One thing I can note that threw me off is I had it running and kept attempting revs with each test I attempted (removing gray wire, removing tan wire, etc), and twice it randomly rev'd all the way up to 6200rpms! I couldn't replicate it, and it only happened twice at different times. Both times however, all wires were attached and it was as it should be electrically.

    Does this make any sense? Beings that it did actually rev up twice, should I be looking into the ignition system now or somewhere else? Any help appreciated.

  4. #24
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Did you happen to check the resistance of the black ground wire that goes from the bed plate to the battery? I'd also maybe check the resistance from maybe a head bolt of each cylinder to the end of the black ground wire. My thought process: I had an issue with my ski before not firing and it was the ground cable corroded internally and was extremely high. Also I wonder if maybe one of the cylinders isn't getting a good ground connection to the crankcase and thus the ground cable.

  5. #25
    I have not checked that ground wire resistance. I did move that ground wire off of the bed plate and onto the PTO cylinder head bolt as advised in another post. Seems to be an electrical issue right?!

  6. #26
    So here's an update. I'm out here tinkering with this thing, and I managed to get it to hit max rpms consistently by slowly rolling the throttle to about 75%. Once I hit WOT, it bogs down and won't go back up. Could this just be a carb issue?

  7. #27
    Well, I've finally got my answers for this thing after it's been with a good local mechanic for a few weeks. He basically went through everything I had already done and here's the findings:

    Spark was weak and sometimes not firing leading to unburnt fuel spitting out of the excess causing the sludge to happen.

    The leaking fuel out of the carb was due to the aftermarket carb kit I used to rebuild them. A gasket on the back of the mag carb was just a hair too small and letting fuel by.

    After replacing the coils, rebuilding carbs again with oem kit, replacing the cdi, it still acted the same way and wouldn't rev up all the way. Little more digging....bad stator. Runs like a champ now. Thanks all for your help input, this is a great forum.

  8. #28
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Thank you for following up with the solution. With all that done, you should be good to go for a while.

  9. #29
    I sure hope so. This Polaris has been a tough one since I bought it but compression is good and now all these issues have been addressed so I'm hoping it runs like a champ now. I fired it up today when I picked it up and it sounds like a beast!

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