FX-1 61x 701 really crackly under 1/4 throttle

550headache

550headache

tobacco grower
Location
tobacco valley
if i want to go cruise around the lake with my buddys my fx-1 is really crackly under 1/4 throttle. i jetted it with the kit pro-tec supplied me with for there pipe. the kit is 120 pilot, 140 high, 2.3 n&s and 95 gram spring(not positave on spring). set the needles like they recommended. really crackly on the bottom till i just start to open throttle then BAM!, shoots right out of water and motor smoothes out. if i open the low screw more(2 turns) it runs better but almost wont start. i went back to a 115 pilot and problem improved alot but still isnt perfect. is it bad i dropped my pilot down? do all 61x 701's act like this or is it just me. anything over 1/4 throttle and she just screams! i couldnt imagine a b pipe in there!!
 
kevbo

kevbo

Location
dfw
550headache said:
if i want to go cruise around the lake with my buddys my fx-1 is really crackly under 1/4 throttle. i jetted it with the kit pro-tec supplied me with for there pipe. the kit is 120 pilot, 140 high, 2.3 n&s and 95 gram spring(not positave on spring). set the needles like they recommended. really crackly on the bottom till i just start to open throttle then BAM!, shoots right out of water and motor smoothes out. if i open the low screw more(2 turns) it runs better but almost wont start. i went back to a 115 pilot and problem improved alot but still isnt perfect. is it bad i dropped my pilot down? do all 61x 701's act like this or is it just me. anything over 1/4 throttle and she just screams! i couldnt imagine a b pipe in there!!
Click to expand...

You can clean up 1/4 throttle by dropping the pilot but throttle response will get sluggish. Any aftermarket pipe need to sputter a little at 1/4 throttle for good response. The bottom screw is for idle only, the pilot is for 1/4 throttle. Installing a 115 gram spring will make both leaner. Check your popoff, a 2.3/95g is as low as I would go.
 
kevbo

kevbo

Location
dfw
550headache said:
Just checked. 2.3ns and 65gram spring. 15psi pop off. What do you guys recommend?
Click to expand...

Install a 95g spring and 120 pilot. This should still be a little rich at part throttle. If you do more cruising than throttle blipping then use a 115g spring.
 
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h2odesperado

h2odesperado

Pin it to win it
Location
Charlotte, NC
My ski does something similiar. Runs well, but I feel it could clean up. I doesn't really hesitate, just makes that popping/gargling noise at 1/3 throttle, cleans out instantly. Occasionally I can get some low-speed hesitation, in between 1/4 and 1/3.

Running a brand new 46 SBN on a b piped 61x cases 62t cyl. (odd I know). Carb has (as every new SBN 46 comes with) 120 low, 150 high, black 80 gram spring with 2.5 n/s for a 14 lb popoff. I have changed to a 95 gram, I think I noticed a difference but probably not.

Debating changing to a smaller n/s, got time to play with it so I might as well tune/experiment/learn.
 
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