Join Date: Feb 2019
Thanked 6 Times in 6 Posts
I ran into essentially the exact same problem you described on the exact same bike. The fuel pressure regulator lasted about a week after "reviving" the bike from sitting for years and then one day it just started running like complete crap, and it ended up being fuel was gushing out of the regulator's diaphragm and there was only like 15psi at the outlet. The bike would start but ran awful, exactly like you described. Very low power, stalling at idle, ect.
I ended up getting a complete used assembly (off a later model, so it had extra wiring for the gas gauge and stuff, but the rest was identical) off ebay and poaching the regulator off it since Suzuki does not sell just that part. I did find a company called HighFlow Fuel Systems, who sells aftermarket fuel pumps, sells replacement regulators for other Suzuki models that look similar (listed as for SVs and V stroms) that I strongly suspect could be adapted to work for the C50 by modifying the clip that holds it in place slightly.
The original filter was also totally blown out/rusted and I think was also contribuiting to clogging the injectors, so I swapped that with the newer one also. While it was apart I tossed the injectors in a ultrasonic cleaner and then blew them out with carb spray. Put it back together and the bike ran like new and has been for several thousand miles now.
Have you tested the new assembly to ensure you're getting ~45psi out the outlet? I mean you'd like to think it's ruled out being all new, but if you have the same symptoms, could very well be the same problem as before (low fuel pressure). Both MAP sensors hooked up? Easy to miss one of the hoses, and if left off will cause a massive vacuum leak and the bike will barely run.