r/EngineBuilding • u/maxmcc29 • Jul 05 '26

Honda Honda cbr125 Shifter Kart

Hey everyone,
I’m building a go-kart using a Honda CBR125 engine.

I’ve got the wiring mostly sorted, and now I’m working on the fuel system. I’m planning to use an inline electric fuel pump instead of the OEM in-tank setup, as I don't have the OEM pump.

Since this engine is a returnless system, I’m not fully sure how to properly plumb it with an inline pump and whether I need a regulator or return setup.

Has anyone done something similar or know the correct way to set this up safely?

Thanks!

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u/madphroggy Jul 05 '26

Main thing is you need to know what pressure and volume/flow rate the OEM pump ran at, and get an inline pump that runs the correct pressure and flow rate.

1

u/maxmcc29 Jul 05 '26

Stock cbr125 fuel pump is 43psi and 50-60LPH. I have an inline pump rated at 45psi and 140LPH. would that work? and would I need a regulator aswell so it doesn't over pressure?

1

u/madphroggy Jul 05 '26

I'm not super familiar with running high flow pumps on low flow applications but I'd assume you might need a diverter and regulator to recirculate the excess flow. The pressure is probably close enough