Super Jet Engine dies under load

[D-Roc]

the low speed needle is for setting a smooth idle. not jetting. if you change your idle stop screw, then adjust your low speed screw for a smooth idle at the new rpm. i always start at one turn out on both screws. ideal jetting would have me at one turn out but with my canadian temp changes i find myself adjusting my High screws to keep it clean running. so it was running good and then someone used your ski when you where not there and now there are problems? maybe don't let your friends borrow your ski............lol, not.

 

[Pablo]

nothing like that...i've got good riding buds and pretty knowledgeable too. I'd trust my ski all day with either of them.

the low speed needle is for setting a smooth idle. not jetting. if you change your idle stop screw, then adjust your low speed screw for a smooth idle at the new rpm. i always start at one turn out on both screws. ideal jetting would have me at one turn out but with my canadian temp changes i find myself adjusting my High screws to keep it clean running. so it was running good and then someone used your ski when you where not there and now there are problems? maybe don't let your friends borrow your ski............lol, not.

 

[Pablo]

PM sent

Are you sure this is electrical? The symptoms you describe make me wonder if you may have a part blocked low speed jet or similar. I don't think it would be the Epic but you could also try the stop circuit to make sure the white is not simply shorting somewhere.
Chris

 

[Pablo]

It took me all day and I practically tore my ski down and put it back together with no definitive answer. I have spark, compression, and fuel.

- pulled Ebox checked connections/Epic wiring (all was good before but just crossing off my list)
- reprogrammed Epic - 3rd time
- checked for spark - yes
- pulled flywheel to check stator position - all good and retorqued with fresh flywheel cover gasket
- pulled water box to check for broken baffle causing too much back pressure preventing combustion - water box good to go
- pulled fuel lines/filter - all fresh
- good fuel flow from pulse line during start
- pulled manifold to check reed condition - I was almost certain I had a broken reed...NOT. Both sets of reeds were good.
- previously I had pulled the carb to check and clean needle/seat, both jets. All was clean and reinstalled, but somewhere in this process I fubar'd my carb (sbn 46)

Ski turns over great, makes good spark, has compression, and has fuel (way too much fuel apparently). After I pulled the water box to check for baffle failure I moved to the carbs to check reeds. At each stage of tear down I would recheck for ignition. With the carbs and mani pulled I just turned it over (don't know why I tried this but it gave me some answers). The ski rumbled to life and burped out a large gush of fuel out of the intake orificies! So ski died out after burning what fuel was present. Reassembled ski and gave it a spritz of starting fluid (no fuel lines connected but carb/mani installed). Ski fired up like it normal and let me hit the throttle and died. Connected lines with fresh fuel. Couple primes and great fuel flow from pulse signal, but no ignition with ski turning over great. Still have positive spark. Pulled carb and hit start again without fuel and it fires up great!
So, I'm guessing my carb is flooding the engine. Do I assume needle/seat bad? The needle tip looked fine, no grooves. Jets were clean and clear.
Carb specs:

SBN 46
2.5 NS
137.5 low (was a 130 weeks ago but changed to accomodate lots of early, advanced timing on Epic curve)
150 high
80 gram (black spring)

Don't have a pop off gauge, but ordering one.

 

[Waternut]

My guess is all the excess fuel is because of all the excess cranking and priming with no ignition and probably not part of the real issue.

I'll throw this into the mix because I don't know anything about them. Pablo has power valves on this engine. Could poor adjustment or some malfunction cause an issue like this?

 

[Breese08SJ]

I had a problem just like this last year. Boat would run fine out of the water, put it in the water with a load on it and it would barely run at all. I chased the "Electrical problem" by changing 4 different CDI and coil combinations and it still ran the same way. I found my real problem by dumb luck by taking off the stock airbox and starting the motor on the trailer, with the motor running one carb had a needle and seat that was stuck open just enough to dribble fuel and flood the motor out and killing one cylinder. Turns out it was some nasty fuel deposits built up on the rubber tip of the needle. Not saying this is def your problem but sounds pretty close.... Just my .02

 

[Pablo]

Paul Lehr asked the same question.

My guess is all the excess fuel is because of all the excess cranking and priming with no ignition and probably not part of the real issue.

I'll throw this into the mix because I don't know anything about them. Pablo has power valves on this engine. Could poor adjustment or some malfunction cause an issue like this?

 

[McDog]

Paul is awesome. Always willing to help even if he has no skin in the game.

 

[Pablo]

I pulled my original SBN 46 and cleaned it from top to bottom. I didn't have a rebuild kit and I think I needed it. I had about 1/8 of my internal carb filter holding a mix of lint and sand. All the jets and needle seemed clean. Some of the gaskets/diaphrams seemed a bit worn but no perforations noted. I put it all back together and it fired up real easy, but ran like complete crap...on the lift. I'm at the point that I think it's a dribbling problem with the needle/seat due to excessive vibration and a low spring rate (80g). The ski will fire but it rumbles and stumbles real hard immediately after you open the throttle and never really cleans up.

On a side not, I changed out my carb to another sbn 46 from a set of duals I have and the ski fired and ran pretty good. There's a bit of hesitation off the bottom but it cleans up real fast. I used the same specs on my last carb that was having dribbling problems so that's a bit strange, but whatever works is fine. I've been told different carbs, although they are the same model, may have a different pop off with the same specs. We'll see how it tunes up this weekend.

 

[Pablo]

good tip...

I had a problem just like this last year. Boat would run fine out of the water, put it in the water with a load on it and it would barely run at all. I chased the "Electrical problem" by changing 4 different CDI and coil combinations and it still ran the same way. I found my real problem by dumb luck by taking off the stock airbox and starting the motor on the trailer, with the motor running one carb had a needle and seat that was stuck open just enough to dribble fuel and flood the motor out and killing one cylinder. Turns out it was some nasty fuel deposits built up on the rubber tip of the needle. Not saying this is def your problem but sounds pretty close.... Just my .02