superjet running on one cylinder(has reworked coil)

[Gainera2582]

Details: Riding out last sunday, was going fine then all of a sudden power dropped down a ton without any prior event. My buddy brian rode the ski and it cleared out and ran with full power. I ride the ski today in the water, and it wont rev out fully. All of a sudden it gained full power back again, but then shortly after it went back to acting like it had no power!!! On land, it seems to rev up fully and not have a problem, which leads me to believe I have a chamber leak again(keep in mind the chamber has been rewelded).

Here is a video of what it sounds like:



YouTube - Broadcast Yourself.

 

[B-Roy]

Anyone have any ideas, help him out!!!!!!

Definatley sounds wierd.

 

[drodabaugh]

I have a Kawasaki that behaved in a similar fashion. It was a failing temp sensor which kept throwing the ignition into "limp mode" thinking that the motor was overheating. It was difficult to troubleshoot since it was an intermittent electrical problem.

Not sure if Yamaha has a similar circuit?

 

[Mouthfulloflake]

could be a bad spark plug, a bad spark plug wire end, could be water in the gas, could be the overheat sensor.

 

[sjetrider]

1st things 1st, check plug wires, this is simplest and most common problem with thes simptoms. If you have an OHM's meter use it, if not take off boots and cut back about 1/2" then use needle nose pliers to pull on copper wire and if any wires pull out then cut wires back to the length of the piece that came out. Start here for sure.

 

[jetskee]

That video sounded really similar to what my Kawi 750 did to me once.
It would run, but vibrated really bad and had no power.
Put new plugs in it and it was fine. I would try that before really tearing into anything....it's cheap, and new plugs never hurts.

 

[sjetrider]

That video sounded really similar to what my Kawi 750 did to me once.
It would run, but vibrated really bad and had no power.
Put new plugs in it and it was fine. I would try that before really tearing into anything....it's cheap, and new plugs never hurts.

I assumed he did that already, but usually plugs would not go good then bad then good in my experience.

 

[wydopen]

intermitant spark from bad plug wires???...could be the temp sensor...thats what the blaster i got did...is it like its hitting the rev limiter??

 

[jetskee]

I assumed he did that already, but usually plugs would not go good then bad then good in my experience.

Yeah, I was going off how it sounded in the video...forgot that part.
I'd still change plugs first anyway.

 

[demolition_x]

i had that same problem on my ski. i trimmed the wires back and it fixed it.

you can always send your coil to JSS and never have to worry about cutting wires again. he does top notch work.

 

[Gainera2582]

Thanks guys so far for the suggestions. Stupid me decided to pull the exhaust off before anything to check for a leak in the chamber(none found so far), so Ill have to reinstall that tomorrow and recheck everything else.

 

[Superjetjim]

Have you checked the little tiny bucket filters in the carbs? - sounds like one is blocked to me and not allowing enough fuel into one of the cylinders - the other is trying to 'carry' the starving one.. you can hear it 'hardening off' in your video..

My ski has done this twice in the past - same thing both times, sounded and behaved just like yours - I run a JSS inline gas filter now.

Pull the carbs and have a look.. they get blocked up with fluff, hair and crap out of gas stations..

 

[B-Roy]

Get it running right yet?

 

[Gainera2582]

Working on it hopefully tomorrow and sunday to get this solved. (btw brian i have your battery and socks to give you back) Been busy with work and graduation tomorrow.

 

[SUPERTUNE]

Pull the F/A off and look down the carbs when running against the dock to make sure you don't have a bad /stuck needle valve and flooding motor killing a cylinder...

 

[Kaveman]

You have MO numbers on your boat. I assume that you are not experiencing these problems in salt water.

Be methodical in your approach. Do a compression test on the engine (doesn't sound like a mechanical problem but if you verify adequate and equal compression you can eliminate it as the source), check for spark at each plug then check for fuel quality and delivery issues.

Once you have found the problem area let us know and further checks can be suggested.

 

[Superjetjim]

Still say its the carb filters - was it running fine then went like this or is it a 'new'/changed setup?

 

[#ZERO]

It's defiantly running on one cylinder and from the amount of smoke coming out the exhaust, I'd be in agreement with Chuck, saying one cylinder is getting flooded out.

 

[Gainera2582]

Ok, decided to put the boat back together and tested compression(roughly 155-160 even on both cylinders, so thats a big relief). Next, I checked spark. Back plug is sparking good on the rear cylinder, where the front isn't sparking at all.

Should I cut the plug wire back or should i test something out first before doing so?

Thanks,


Aaron

 

[Mouthfulloflake]

cut them back
some autoparts stores will sell spark plug ends for 24 cents or so each.

trim it back to good wire, crimp and solder that new connector to your wire, and you will be good to go.