Gz250 gasoline fills the Air filter

wacio · 10-22-2019, 04:47 PM

Let me clarify something here for all GZ250 users.
GZ250 was designed to have safety redundancy preventing gasoline overflow into engine (most motorcycles do). Both petcock and carburetor needle valve operated by float have to fail before fuel overflow occurs. So if you have fuel in airbox or in oil you need to fix two separate issues:
1. You need to rebuild your petcock (or better yet - replace with manual one).
2. You need to take carburetor apart and make sure that float is good and valve it closes has good seal (both needle in the seat and seat in the carb body). Float needs to be adjusted so when needle valve closes (not carb upside down - service manual is actually wrong here) lowest part of float is 13 mm from bowl seal surface). Carburetor upside down causes float to not only close the valve but also collapse vibration dampening/overload spring inside the needle. Adjusting float with carb positioned upside down will result in fuel level too low.
Starting and running engine with both petcock and carb float needle valve leaking, is the best way to cause catastrophic engine failure. You may hydro lock the engine or cause to run it without lubrication - both not a good thing.
I recently noticed my engine getting hard to start if seating for just few minutes (would flood and need long crank with fully opened throttle). I have manual petcock and always close it for parking. Took carb apart - needle was good. Took seat out of carb body and oring around it was completely deteriorated. It was allowing gas flow around valve to fill bowl regardless of the float valve. It was happening fast enough that stopping engine for fill up at the gas station would end up flooding it. Leaving overnight could result in filling crank case and air box completely.

10-22-2019, 04:47 PM	#6
wacio Senior Member Join Date: Apr 2016 Location: Illinois Posts: 174	Let me clarify something here for all GZ250 users. GZ250 was designed to have safety redundancy preventing gasoline overflow into engine (most motorcycles do). Both petcock and carburetor needle valve operated by float have to fail before fuel overflow occurs. So if you have fuel in airbox or in oil you need to fix two separate issues: 1. You need to rebuild your petcock (or better yet - replace with manual one). 2. You need to take carburetor apart and make sure that float is good and valve it closes has good seal (both needle in the seat and seat in the carb body). Float needs to be adjusted so when needle valve closes (not carb upside down - service manual is actually wrong here) lowest part of float is 13 mm from bowl seal surface). Carburetor upside down causes float to not only close the valve but also collapse vibration dampening/overload spring inside the needle. Adjusting float with carb positioned upside down will result in fuel level too low. Starting and running engine with both petcock and carb float needle valve leaking, is the best way to cause catastrophic engine failure. You may hydro lock the engine or cause to run it without lubrication - both not a good thing. I recently noticed my engine getting hard to start if seating for just few minutes (would flood and need long crank with fully opened throttle). I have manual petcock and always close it for parking. Took carb apart - needle was good. Took seat out of carb body and oring around it was completely deteriorated. It was allowing gas flow around valve to fill bowl regardless of the float valve. It was happening fast enough that stopping engine for fill up at the gas station would end up flooding it. Leaving overnight could result in filling crank case and air box completely. Last edited by wacio; 01-01-2020 at 07:21 PM.
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