Thread: 96 SLT780 - The PWC from HELL!
06-01-2012, 09:08 AM #1
96 SLT780 - The PWC from HELL!
So I started working on this 96 SLT 780 I purchased last Fall. Cant get it to rev up, it just has no power. Rebuilding the carbs made no difference. Here is what Ive tested so far:
Compression - All within 1 PSI of each other.
Index - CNT is dead on, PTO is .5 degrees off.
Fuel pressure at idle is 2 PSI tested at the mag carb.
Carbs are clean and new diaphragms installed.
Stator Tests below done with a nice fluke. Lead resistance of .2 ohms subtracted from results:
Red/Purple - Yellow = 6 ohms = Good
White/Yellow - Black = 216.1 ohms = Good
Blue/Red - Red/White = 89.4 ohms = Good
Red/White - Green/Red - 462.4 ohms = Good
Swapped CDI with 95 SLX CDI
Coils = .2 ohms each Measured with two separate meters.
The pto cyl gets hot, all others cold. If i switch the spark plug wire order, the cyl that gets hot does not change. The ski will not run at all without the PTO cyl firing.
Here are the questions:
The book said that the coils should be .6 ohms. I saw one reference on the forums that the acceptable range is .2 - .6 ohms. IS this accurate?
I would think the coils were the issue, but Im leaning towards an issue with the carbs considering that only one cyl is really doing most of the work.
Ideas? (No I have yet to do a leak down test).
Last edited by ghostinstallations; 06-15-2012 at 04:57 PM. Reason: Title Change
06-01-2012, 10:16 AM #2
If you remove the PTO wire, can you get the other two to fire with premix down the carb throats?
What are your compression ratings, other than 1 psi between each?
Did you remove and inspect the reeds?
06-01-2012, 10:23 AM #3
Have you used a spark tester and verified spark at each of the wires? Have you replaced your plugs with BPR7 or 8ES plugs lately? There is spark on all, verified with a spark tester. Spark seems to be consistent between cyl's.
If you remove the PTO wire, can you get the other two to fire with premix down the carb throats? Have not tried...I can see fuel spray down the carbs.
What are your compression ratings, other than 1 psi between each? Compression is about 125.
Did you remove and inspect the reeds? No, plan to after I run a leakdown. I figured my compression would suck if there was a damaged reed.
06-01-2012, 11:24 AM #4
I would check your reeds!!
06-01-2012, 12:19 PM #5
Leakdown test = Good
Reeds = Perfect. Could not slide a feeler under any without them flexing
Carbs = Good
Went thru again. Very clean, set screws to specs in manual. Verified I am using the correct settings for the 03 780 engine. (Verified it as an 03 by serial number and by verifying the position of the first transition hole in the carbs.
Found that one of the leads to the CDI was disconnected from the last time I took it apart to test the stator. It now revs more out of the water 4-4500 RPM. This is what it did last year when I purchased it.
In the water it wont go over 2500 RPM. Fuel pressure is 4.5 PSI WOT.
Guessing at this point it is a coil problem, maybe a stator problem. What a PITA. Cant believe I have spent well over 15 hours on this ski and gotten no-where.
06-01-2012, 05:00 PM #6
- Join Date
- Oct 2006
- Cleveland OH
4.5 is acceptable, but should really be closer to the 6 PSI mark at WOT.
Have you checked out the piston wash?
Have you tried cutting the plug wires back 1/4" yet?
Is your exhaust hose REALLY soft and mushy?
06-01-2012, 05:41 PM #7
wires have been cut back twice.
checked temps everywhere. i can touch everything without issue. Rubber couplers are firm when engine is running.
I think i need to rip the coils out of my slt750 and try them in the 780. if that does not fix it, i am going to try to buy and install a stator. The static test for the stator shows its fine, but maybe it is breaking down when it is running.
As for fuel pressure, i would agree, but I assume the pressure will be higher if it would rev pas 4k.
thanks for the input so far!
06-14-2012, 10:21 AM #8
Swapped the coils with ones from my 94 SLT 750 that runs great. No dice. Removed MFD. No Dice.
At this point, the stator has been checked a million times. Im going to verify timing and then replace the stator anyways.
In its current state, if you ease into the throttle, it will rev up to 4k and then jump pack and forth between 2k and 4k every few seconds. Any other ideas?
06-14-2012, 11:30 AM #9
06-15-2012, 05:09 PM #10
Today I verified timing. BTW, what a PITA! Not only do the fujis not have decent timing marks, but because I have a 03 780, The timing verification is to be done at 1500 rpm. So after having to measure TDC then mark 26.5 degrees, I then had to turn the idle down so that out of the water it would run at 1500 RPM. At that low a speed, it was VERY hard to read the timing mark as it was bouncing all over. Typically, it seems much easier to use a timing light at higher engine speeds, but because of the curve of this CDI, it made it a pain.
Also took apart the fuel pump even with the good fuel pressure test. Clean and i believe recently rebuilt as I was able to separate the diaphragms and gaskets without damage.
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