superjet runs great for 5 min then bogs to idle

kwakhead

kwakhead

Location
macomb
Just as the title says. I'll take it out, it will run OK for about five min, then won't go full throttle only half, then 5min later only quarter, then it won't go over a quarter for longer then 10 sec without bogging to idle or shutting off.
Engine is nice and COOL
Fresh rebuild top and bottom, compression and leakdown is good
Has case porting and cylinder porting, just rec port jobs though, getting the carb jetted where it should be at but it makes no difference as of now, ski runs the same
Cleaned the carbs, fuel lines, fuel take, checked the tank check valve, replaced it, fuel system holds pressure..
So I'm believing it has to do with the electrical system, the stator is newer as in last year, so I'll count that out. I'm replacing the 61x cdi with a spare 6m6 I have, and also replacing ignition coil. Both of these items came off a good running ski... I will post my results... Oh, and the heat sensor us cut, ski is not going into limp mode unless it is malfunctioning in the cdi. (Or wires could be arking each other)). .... Any help appreciated, tomorrow I'll have pretty much covered everything so I'll let everybody know how it goes.. Oh and plugs are dark, but I've never really had problems running dark or foul plugs to be honest here however stupid that may seem lol
 
BIG JOHNSON

BIG JOHNSON

Location
Cornelius, NC
I my old 750 would start to run horrible after riding long enough to warm up. Turned out to be the ignition coil.

In my case it was intermittent and wouldn't get progressively worse like yours sounds. The warmer it would get, the more it would miss. It felt like it went from running fine to running on one cylinder, and it was instant. It would come back to running on both and be fine for a second, then get to the point where it barely stays on plane.

I know it sounds cray, but I would bring a couple bags of ice and strap it to the e box and see it if holds off the bogging. It's not a fool proof diagnosis but it couldn't hurt to try and rule out a temperature related electrical gremlin.
 
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kwakhead

kwakhead

Location
macomb
Tried a new cdi and a new ignition coil!!!!! Still runs the same. It will run fine if I open it up for literally 2 seconds then it bogs down to idle and shuts off. Its not in limp mode as I can still give it throttle and the rpms will climb...
 
BruceSki

BruceSki

Formerly Motoman25
Location
Long Island
Check fuel tank vent?

Check return on carb that it's not clogged?(pull return on tank side while ski is running on trailer and see if fuel comes out)

Ohm out stator? Heat soaked and malfunctioning once running
 
kwakhead

kwakhead

Location
macomb
Tomorrow I'll clean out the carb again.. I didn't clean the return, I don't think its clogged, but it could be clogged enough to restrict flow at higher rpms...
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
Have you run it with the hood off to see if it will still do it? That would rule out air starvation, exhaust leaks as well as fuel leaks. It might help with the temperatures too.
 
kwakhead

kwakhead

Location
macomb
Every time I run it with the hood off on land it runs fine, I'll try in water tomorrow... Tommorow going to try
Replacing check valve with different
Possibly fuel system not holding correct pressure?
Check the return on carb
Try running with hood off

My bet is its not getting enough fuel once I get going so its returning to idle... It doesn't have any exhaust leaks, I've ran it and watched many times... Air starvation seems unlikely since its a stock hood but I'll see....
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
I was going to ask about the coupler. It sprays a ton of water into a fine mist that would definitely cause what you are describing. There was a thread on it a few years back but good luck finding it.
 
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