Super Jet Help! 781 Flame in fuel line, stumbling & rough idle

[Circus]

I've Had my 98RN with 781 on the water approx 8 times now, just before trailering and heading home the ski started running like it was only firing on 1 cylinder. A quick check revealed good plugs and spark to both.

When I got it home and tried to run it on the hose it started rough and wouldnt idle w/out at least half throttle. It sounds like its sucking air at the wrong time. I noticed a small exhaust leak out of a coupling on the speedworx pipe and also noticed that there was flame running in the T-d fuel line on the engine side of the rear carb every time it gasped and stumbled. Engine got hot quickly even with backflush running. Afterwards the rear plug was covered in black tar. Going to attempt to tear into it tomorrow if the weather cooperates but i was hoping someone had an Idea of what may be happening.

That's the best picture I have it's dark and raining now but the circled line on the front carb corresponds to the fuel line on the rear carb that has flame running in it.

 

[Matt_E]

That's the pulse line. Are you getting backfires?

 

[Circus]

That's the pulse line. Are you getting backfires?

Sounded like it was backfiring off the rear only but not consistently and the pulse line kept lighting up every few seconds. I didnt pull the flame arrestor because it starting pouring had to button everything up and run inside.

 

[964Chris]

think the timing may have slipped (loose stator/sheered woodruff key)?

 

[Fstrkls1]

Check your reeds sounds like a broken reed

 

[Matt_E]

Check your reeds sounds like a broken reed

Pulse is taken after the reeds, so that's probably not it. I'd check the woodruff key.

 

[Marcgraham27]

I have seen it happen from reeds

 

[964Chris]

we're gonna go through some things today. will definitely pull the flywheel cover and take a peak in there. will also go through the carbs to see if maybe there's a stuck needle etc. and have a look down the intake at the reeds. I haven't seen or heard the issue yet. Just trying to get some ideas before he brings it over.....anything else I should be looking for?

THANKS

 

[Circus]

I'll get a few pics and a video if possible, but the flame happens so fast its difficult to see it even in the dark.

 

[Circus]

NDB, Found the Problem...Nothing a little JB weld can't fix.

 

[BombThreat]

thats a good one

 

[Circus]

tear down

 

[964Chris]

First thing I did was pull a compression check......BINGO 170ish front 30 psi on the rear. That rear cylinder had an ate up piston, looks like the ring caught on the exhaust port and went to town. The front cylinder also looks like it ate something aluminum at one point. Has an aluminum streak that is embedded into the cylinder wall now.

The coupler that goes from the manifold to chamber (speedwerx) had a big gash in it....so there was an exhaust leak.

Carbs looked good, filters were clean, gaskets were good, no stuck needles. Fuel, return, pulse lines were all pretty loose/easy to pull off. Advised to find some OEM fuel lines.

Flywheel was good to go, nothing loose or floating around under the cover.

Could the exhaust leak cause this problem? I'm thinking it was a lean condition or water intrusion. He's running tau ceti/hot products filters no outerwear and his ski lets in a ton of water.......he's looking for a stock f/a setup now lol.

 

[Circus]

I figure a loss of back pressure could cause an over-scavenging effect, but the plugs were running dark chocolate.

 

[Yamer-Jammer]

I have read before that if you don't have the ports in the cylinder sleeve chamfer bored (grinded at angle), is a common cause for a ring to snag.