Surging Problem

[Hi-z]

Hey guys, new here but hope you can help
Picked up a used 04 Sportster 883.
Had to replace the carb, picked up a used one
(HD CV) for same bike.
Started ok but seems to surge,
Surges up to 2500-3000 then slowly back down to idle.
No vacuum leaks I can find.
Diaphragm is not ripped
Any ideas where to start next?
Thanks

[coasty]

Originally Posted by Hi-z

Hey guys, new here but hope you can help
Picked up a used 04 Sportster 883.
Had to replace the carb, picked up a used one
(HD CV) for same bike.
Started ok but seems to surge,
Surges up to 2500-3000 then slowly back down to idle.
No vacuum leaks I can find.
Diaphragm is not ripped
Any ideas where to start next?
Thanks

Check to see if the throttle cables are properly adjusted.

[Hi-z]

Well it was a vacuum leak
Crack in the manifold
JB Weld and took care of that
Now to figure out if it needs rejetting
Back firing when you give it gas
Not all the time but most
Tried adjusting the fuel mixture but no changes
Thanks again

[Hillside]

Keep an eye on that JB Weld!
Start off with a 45 pilot/170 main/3 turns on air idle.

[Hi-z]

Making sure no other vacuum leaks
Pulling carb apart and cleaning all passageways with GumOut again
Filled fuel bowl half with gum out and rest gas
Cranking mixtures screws out about 5 turns
Running sea foam for 20 miles of hard riding.
Runs pretty good right now
Sometimes hesitation on accelerate with some back firing
Does it sound like still running lean?
Any idea on jet size?
Thanks again

[claydbal]

lok at hillsides post for jetting. then (if you think cleaning a carb is done with chemicals) replace jets with new. install new plugs, then you have a starting point. dont trust the j-b weld, or the manifold seals. bit this will give you an idea and a practical starting point.