Post by woowilly on Mar 31, 2013 21:36:01 GMT -5
a while back I bought a dead gy6 150cc scooter with 10 inch rims, It ran after I repaired the open ground problem.
the top end had a lean surge, going to a # 112.5 main jet fixed that. ( just a hair rich though.)
hard to start, backfired out carb when the throttle was opened when it didn't just die.
moving needle clip to raise needle and opening mixture screw to 3 turns out helped.
( No rpm drop off when the mixture screw was opened past the peak rpm indicated slow jet was too small.)
going to a # 38 slow jet gave a sweet spot at about 2-1/2 turns out.
I set it to 2-3/4 to be just slightly rich for easy starts and to make it easier to get off idle with no accelerator pump.
Then I gutted the muffler. ( all else is stock )
that made it hard to start when cold, and die if the throttle was snapped open, even when warmed up.
I went to readjust the mixture screw and found 2-3/4 turns was right at where it was too far closed,
and no rpm drop off once past the rpm peak like I need an even bigger slow jet.
I set it at 4 turns out for now. Starts easier, doesn't die getting off idle, less deaccel popping out the muffler.
Main jet size requirement seems pretty much unaffected.
I've read is that going to a # 38 slow jet when doing just filter & muffler performance upgrades isn't really needed.
Has anyone else had to go bigger than a # 38 slow jet for just a muffler mod?
( or for any other reason? )
the top end had a lean surge, going to a # 112.5 main jet fixed that. ( just a hair rich though.)
hard to start, backfired out carb when the throttle was opened when it didn't just die.
moving needle clip to raise needle and opening mixture screw to 3 turns out helped.
( No rpm drop off when the mixture screw was opened past the peak rpm indicated slow jet was too small.)
going to a # 38 slow jet gave a sweet spot at about 2-1/2 turns out.
I set it to 2-3/4 to be just slightly rich for easy starts and to make it easier to get off idle with no accelerator pump.
Then I gutted the muffler. ( all else is stock )
that made it hard to start when cold, and die if the throttle was snapped open, even when warmed up.
I went to readjust the mixture screw and found 2-3/4 turns was right at where it was too far closed,
and no rpm drop off once past the rpm peak like I need an even bigger slow jet.
I set it at 4 turns out for now. Starts easier, doesn't die getting off idle, less deaccel popping out the muffler.
Main jet size requirement seems pretty much unaffected.
I've read is that going to a # 38 slow jet when doing just filter & muffler performance upgrades isn't really needed.
Has anyone else had to go bigger than a # 38 slow jet for just a muffler mod?
( or for any other reason? )