Super Jet need help with low rpm break-up and loss of power...

[aramis]

Ok, here's my problem:

Ski has been running great for the last 12 hours out or so with gobs of power down low after putting in the EPIC, and then:

3 rides ago, the ski started to "miss" or "sputter" at low rpms after about 1 hour of riding. It never stalled, but was bad enough to screw up the exit of a few slides and spins. Actually figured I was just getting low on gas, but that wasn't it.

2 rides ago, it did the same thing at the 1 hour mark, but a bit worse...still missing or sputtering, but also almost cutting out completely like it was really lean down low.

last ride, it was missing and sputtering down low right away (after 3 minutes), and progressively getting worse throughout a 1 hour ride, to the point where it didn't ever run right at low rpms.

In all cases, it was OK at 1/2 to full throttle.

Ski details:
- EPIC ignition put in about 12 hours ago, replaced Enhancer
- new OEM coil, with JSS wires about 12 hours ago (just to replace crappy MSD coil)
- 62t/61x
- stock 38 carbs
- 70 Pilot, 135 Main, 1.5 N&S (don't know what spring - it's silver)
- b-pipe, top screw open 1/2 turn, others closed
- ADA head w/ 35CC domes


Any ideas? Here is what I have checked so far:
- compression was 180 F / 182 R when I checked 4 or 5 rides ago, forgot to check again
- no blown o-rings
- piston wash looks OK to me, but I'm running Castor 927 so I'm not sure. I'll post pics.
- plugs definitely did not look lean, they were a dark brown.
- reeds are all original SS, all look OK (they seal tight and no visible cracks)
- pulled carbs apart
- internal filters were clean (new last year)
- no visible wear rings on needles
- everything else looked pristine
- there was some minor gummy gas stuck to the insides of the Prok F/A "tips".
- stator plate is nice & tight, and both marks are lined up
- I need to replace the lighting coil now, since I nicked it with the puller bolts
- little bit of oil sitting on the pulse coil wire, where it bends and the outer insulation
created a gap.

When I checked compression before this problem started, I didn't ground the plug wires. But, I did hold the stop button in while cranking. Is that the right way to do it? Could I have damaged the ignition coil?

I always use 93 octane, but have been forced to use 93 octane w/ 10% ethanol lately. Could that be part of it?

I'm about to order a pop-off tester and some springs, jets and all 3 stator coils. I think I should get a bigger Pilot jet anyway, now that I'm running the EPIC...but it's been running freakin' great up until 3 rides ago.

What else could it be? Thanks!

 

[OCD Solutions]

Do you happen to charge your battery between rides?

 

[aramis]

nope, I never do. It's a sealed battery (Cycletron, I think) that's 1 year old now.

I also leave the lanyard in.

 

[aramis]

Here's the piston wash pics...pic on left is the rear cylinder.

 

[QJS]

If it ran great up till 3 rides ago your jetting should be fine unless you have had a recent significant temperature or altitude change. Couple of other things to check.....make sure the two round plastic discs in the fuel pump have no creases or imperfections, this is sometimes difficult to see with the naked eye. Also check the exhaust hose does not run anywhere near the holes in the diaphram covers, when the exhaust tube is hot and the engine is at maximum vibration at low revs you would be surprised how easy it can restrict the holes in the covers, this is common if you have a manifold spacer, tell tale signs are rub marks on the diaphram cover. Other one is a loose baffle in the waterbox but this would most likely feel rich.
Chris.

 

[augustaf]

It's possible the charge coil in the stator could have gone "bad". It actually gets quite warm during use and "print through" of the windings could increase after extended use. I've seen a few oem coils fail. Don't even consider that a/m replacement- it might not last a tankful.

 

[aramis]

I didn't think about the diaphragm holes, but I checked that and there's no rub marks.

I'm thinking it's the charge coil now, and am gonna order from AJS. I'm assuming it's an oem they sell, not an a/m...?

Could it be the battery and/or lighting coil? The ski sat for 2 weeks and ran fine, but those last three runs were back-to-back fri-sun.

Still scratching my head on this one...