FX-1 Fouling Plugs

G

Goose

Location
Maryland
701 61x completely stock, low hours
B pipe
Mikuni44
-95 gram
-140main
-120 pilot
-1 1/2 high speed, didn't touch low speed after engine swap.
-A/M Flame arrestor
Newly replaced coil

Ski rips great and idles well, no hesitations and runs like a bat out of hell BUT at any short idle or even if you kill the engine and try to start again the plugs will foul out. I even road specifically to avoid fouling by never idling and it was unavoidable once the engine was killed and restarted. I was running 40:1 on 4 gallons of gas in tank and fouled so I added 1 gallon of gas to ski to bring it to 50:1 and it still fouled plugs out. I also replaced the coil and ran it on what were previously fouled plugs and it ripped hard which confused me. If the plugs were fouled how did it push through then, but won't afterwards, did the cylinders dry out? Was thinking of replacing the CDI next and after that I don't know what else to try. Thoughts?
 
G

Goose

Location
Maryland
I pulled it out of the water fouled, it sat overnight and then I swapped the coil and before I put the new plugs in it ran great until those fouled. Put new plugs in, diluted gas ran until fouled again. It takes aprx 5-10 min to foul.

I'll have to lookup how to test the needle and seat and may just replace them. Could you help me understand better what the needle and seat do and what issues they can cause?
 
G

Goose

Location
Maryland
I never performed a pop off test, I just stuck the 95gram spring in per Factory specs for the pipe. I do not have access to the ski until July, is there a best guess at what size needle valve I should grab? What is stock in the mikuni 44?
 
badvinny

badvinny

Location
Saskatoon,SK
My FX1 started to foul a plug while I was doing tricks behind a buds boat. One last big 180 off the wake end up with a broken elbow, wrist, a separated shoulder and a lot of blood in the the boat! A free airplane ride, a 3 costly ambulances!
 
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G

Goose

Location
Maryland
Swapped CDI it ran much longer but still eventually fouled the plugs. It seems like it's loading up with fuel below 50% throttle sometimes it blows it out but eventually it fouls out and won't run well past 40/50% throttle...fouled plugs. I know I'm mixing exactly 50:1 I don't know how it can be loading up like that unless I'm stupid and it's as simple as closing down the high speed screw. Why is it that the low speed screw won't turn more than 180? It's like it's designed to have a very limited adjustability range whereas the high speed is literally a screw.
 
tomski

tomski

X
Location
LHC
Goose said:
Swapped CDI it ran much longer but still eventually fouled the plugs. It seems like it's loading up with fuel below 50% throttle sometimes it blows it out but eventually it fouls out and won't run well past 40/50% throttle...fouled plugs. I know I'm mixing exactly 50:1 I don't know how it can be loading up like that unless I'm stupid and it's as simple as closing down the high speed screw. Why is it that the low speed screw won't turn more than 180? It's like it's designed to have a very limited adjustability range whereas the high speed is literally a screw.
Click to expand...

Remove the plastic cap.
 
G

Goose

Location
Maryland
Been fine tuning the carbs now and noticing that as I adjust low speed or high speed it effects the other. Very cool. The biggest change came after I swapped the stock flame arrestor in for the after market prok. I'm sure this changed the mixture but I think I was taking in water which was preventing me from fine tuning the carb. Thanks guys for the help.
 
G

Goose

Location
Maryland
*SOLVED*
Ok, so after like 4 years of this never actually clearing up for good, I tore the ski down one more time and noticed, by chance that the exhaust hose to the hull exit pipe had a very weak spot at the 45 bend from the water box. I replaced it with a rad dudes silicone and can positively confirm that this was my issue all these years. It was pinching off, and choking the motor.
 
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