Replaced my fuel pump with eBay purchase, now bike runs like a carb bike. Cold natured, serious off idle stutter... High rpms are fine.
Any ideas?
Bike has decat, stock eexhaust otherwise, KN filter, non CA model.
Took tank off to fix a ding, broke stock pump in disassembly. Worked fine previously. Would a juice box or PC be the answer?
Have run the TPS diagnostic, it's within normal limits.
Sounds like the pressure relief valve is not holding pressure during low use times like idle and off idle response.
If perhaps the tank fell and broke the pumps housing and you still have it, you could pull the pump and swap parts internally. If the replacement pump ingested debris, it may not build adequate pressure or the relief valve may be leaking from debris being stuck in it. You can't fix the pump motor itself but you could swap your old one in.
The valve can be swapped or cleaned, but the pump if worn internally would need swapped to have adequate pressure. If you look at the pump housing it has tabs around the perimeter that when depressed allow it to be disassembled. Carefully pull it apart using the tabs and extract the motor and valve.
At the top of the pump is valve that can be removed, it controls the pressure. It should hold up to 36 PSI but you need a gauge to test it. It's likely it has something stuck in it so its leaking very slightly which under load of acceleration, makes the bike stumble.
That would be my guess if NO OTHER changes were made. However, if it were mine, I'd swap the pumps electric motor too (from your old unit). Also examine the mesh screen filter too. use the cleaner of the two. Also you can backflush it with soap and water to clean it. Make sure its not plugged but the screen is not impacting low speed use.
If you kinked the outlet hose, it would run out of power up high under load, so because it fails in this manor, I vote pressure regulator. See blue arrow in picture. That's the Pressure Regulator.
Take the broken one apart first. You have nothing to loose there.
