Super Jet RN SJ -2" Fast Elements, DASA, Skat Mag, Cold Fusion Build up

Proformance1

Proformance1

Liquid Insanity
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New York Crew
Me too Bruce, I'm getting very frustrated.

Update. I removed the carbs last weekend for anyone who is reading all of this, but I was told by two professionals to do it again and inspect everything. Especially the pump side with the clear plastic parts. A backfire or kickback can break one of those and cause more backfires.

I was completely frustrated after the new stator install, MSD Enhancer backfire. but I went and took the carbs off anyway. Inspected all. Averything looks as new. Reinstalled, changed front pulse line as all the on and offs have started to create a small tear, didnt appear to go all the way through, but 50 cents for a OEM fuel line is nothing compared to what I have spent on the rest of this mess.

Fired it up and its fine, reinstalled the Epic and its fine. I have ran it 6 times so far today, even had what I thought should have been a backfire when the motor and bendix released at a bad time trying to start. Everything is fine. Again it is an intermittent issue.

The saga goes on.

For what its worth, I also checked cyl PSI last night to be safe also. Front cyl 185, rear 183 PSI. So that is reasonable. Checked crank timing with Epic, it was 14-20 degrees advanced. More than I expected with the curve I have loaded but no different from MSD. Wish I could measure cranking RPM. I used to have a Snap On timing light that would do it, It had a digital tach and timing adjust, but not any more.
 
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Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
Zack, I'm ready to flip out, its only a matter of time before i break a wrist pin bearing and destroy this motor. This is stupid, I know others are having this same issue. Someone has to know something about this!

Today I went to the shop hoping for the best. Started the motor today, its fine. Got the hose out and ran it for a while to warm it up. Backfired the first time I restarted it.

I figured that if it was fuel related like a bad new tank check valve I could rule that out by loosening the gas cap. I did, nothing same issue, tried it a few times to make sure.

Closed the High speed jets totally to help rule that out partially, as there is still some fuel that just goes right through the jet itself. Bang, same issue, tried it after running a bit on the hose to help clean any residual fuel out, same issue.

All that I can come up with now, is a blocked water box baffle, or pop off to low at 22-23 psi. I am told this is fine and just checked it last sunday.

How about oil, can i use yamalube with a PV motor? Considering they make PV motors I assumed I could. Not really sure how this would affect the backfire issue??
 
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Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
One thing I should mention is that I have established a pattern for mine. Besides the original kickback caused by the low voltage battery, Epic combo. It only backfires after the motor is partially warm, and or after the carbs have been left on for some time. In other words, if I remove the carbs and take apart, it will not backfire for a while. Not sure how this relates, but i am sure over time, it will make sense.

Just had another thought sitting here reading the Mikuni manual. Would more rigid engine mounts from stock with a lower pop off combo cause the regulator diaphram to pop early and allow extra fuel to flow into the high speed side faster than normal? This could allow fuel leakage and cause the backfire, correct?
 
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Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
There is something to my theory. Narrowed it down more. Changed pop off from 22 to 26 psi, ran the ski for a while on the hose and warmed it up good. Just broke 5 hours on the hour meter. I didnt rejet so its probably a little lean on the bottom now. Problem is mostly gone. It did it once but very very mild and only after I shut off using the full throttle hold after hitting the kill switch.

This brings up and interesting theory. I never really started holding the throttle down on shut down until a few years back at Daytona after discussing with some X Scream guys. It makes sense to me to do this as it does kind of flood the motor, coat the bearings and pistons, and makes it easier to start the next day. Im wondering if my habit of killing it and then going full throttle is flodding it and causing my backfire issue as there may be too much fuel at start up? I think the jetting on the top end being a little rich may also "fuel" this issue also. Currently im at:

127.5 Mains, 1 turn out
120 Pilot, 1 1/2 turns out
2.0 N/S
95 gram spring
26 PSI pop off
 
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D-Roc

D-Roc

I forgot!
Location
Dirty River Rider
Brian, that is the same jetting i have but with 2.5n/s and 18-20 psi pop off. These are on my 48 powerbombs. I run 32 degree static as well. do you happen to have clear pulse lines? I have had fire shoot up mine when my cases get flooded with fuel.
 
Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
I have all OEM fuel and pulse lines. I wanted the reliabiliity, LOL Really made a difference for me going all OEM parts. No issues with the build. J/K


I had 2.3 N/s and 22 psi until today

How often do people have backfires with their skis and dont even know it. Without a PV motor I would never even know about it. Is this common?
 
D-Roc

D-Roc

I forgot!
Location
Dirty River Rider
My ski does not usually backfire, when it did in the past it was from the fuel pooling in the cases and then being started. It was very noticable. The clear pulse line allowed me to see the case backfiring. Its only happened to me twice, Both times was when i had my ski, turned carbs down on the stand to work on something, and left it over night.
 
Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
Yeah I think i rode the electronic thing into the ground, now Im on a fuel quest. I think im dumping fuel for some reason. After spending the day working on the Full Specs and reading the Mikuni manual for the 5th time, and combing over the flow chart, I believe that it has to do with fuel. Could still be a broken water box baffle also, but I'm going to try and jet it next. I will have to put an E box back together for water tests.
 
Proformance1

Proformance1

Liquid Insanity
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New York Crew
Well, spoke to Frosty, Patch, Wammer, Chris and all said go ride the damn thing and get the fuel out of the system and take it from there. Thanks to Frosty for sitting on the launch making sure I was fine out there today. All went great, tuning is not perfect yet, but problems seem to be gone. The issue may heve been fixed with something I did last week, but I could not tell by running it on the hose, the only way to get the fuel out of the system is to ride it. After the 3" snow the other day I figured we were done. It was perfect out there today. 2-3' mostly clean water was 50 deg air was 60. My hand warmers even work now. Still working on the jetting and cooling but she is close enough to ride. Im thinking NC or Daytona bound this winter for the ski.

FYI, I reinstalled the Epic today before I went out. Thanks to all for all the help. Hopefully it stays good
 
Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
I think the stator or somehing fixed it but i didnt know because i was running it on the water hose and not in the lake. The exhaust was not getting hot enough to burn the fuel left in the system. That is most likely why the backfire got less after the new stator etc
 
Proformance1

Proformance1

Liquid Insanity
Location
New York Crew
Steve Frosty and I were having a long discussion about this topic at breakfast yesterday. I now consider this my 2 stroke college education, well at least a semester. I now know more about carbs and 2 strokes than I really care to, lol
 
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