Pump around system

O

Outlaw69

New member
Putting a trx450 together for the kart. Is there a need to run a pump around system? If not what kinda fuel pump is everybody running and does it work properly?
 
I did the pump around(return line) on my 420cc predator, seems to make it more consistent as fuel pressure is far more stable. I didn't modify my carb like some do, just added a "T" in the line close to the carb, ran a return line back to the tank then restricted it with a drilled out main jet stuffed into the end of the line where it attaches to the tank. Adjusting the size of this jet adjusts the fuel pressure to a certain point which can change jetting...keep that in mind.
 
i dont run a pump around system on my CRF450R trannyless engine either and have yet to have an issue. the only reason for the fuel pump is to supply the carb with fuel. nothing more nothing less.
 
Outlaw69 said:
Putting a trx450 together for the kart. Is there a need to run a pump around system? If not what kinda fuel pump is everybody running and does it work properly?
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Assuming by "pump around" you are talking the shifter kart type setup with two fuel pumps? Or are you talking about one fuel pump with an inline T somewhere?
 
FWIW I tried without a return and the pump we use..the round mikuni does overrun the stock needle and seat....we have been running a return with a valve off an old honda oddessy either fl250 or 350 and part# 16710-VM0-770 to further that I felt it bypassed a little too much fuel back too easily so I added a restrictor in the return line (old briggs jet). It works great for us running gas. If we build one for alcohol I imagine we can reduce the size of the restrictor even more as it will use nearly 2 times the volume. The pump I use is the same style I used to supply twins on alcohol..so with less of a pump you may get by without the return.
 
tchase said:
FWIW I tried without a return and the pump we use..the round mikuni does overrun the stock needle and seat....we have been running a return with a valve off an old honda oddessy either fl250 or 350 and part# 16710-VM0-770 to further that I felt it bypassed a little too much fuel back too easily so I added a restrictor in the return line (old briggs jet). It works great for us running gas. If we build one for alcohol I imagine we can reduce the size of the restrictor even more as it will use nearly 2 times the volume. The pump I use is the same style I used to supply twins on alcohol..so with less of a pump you may get by without the return.
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I also run a pump around system. My set up uses two Fuel Valves, one on feed side one on return side. This allows you to set fuel PSI at any level you need. No Restrictor on jetting needed, with round pump.
 
Found on another post about a dellorto fuel pump with a valve in it. No pump around needed. Goggle it. Good info. I ordered one 39.00
 
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