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[pintheair]

hi there,  putting a chainsaw engine in a boat.  problem is , runs great with the original fuel tank in situ,
 but only runs for a few seconds with new tank from  pmb.   got new pipes for flow and return,    can anyone  help.

[Bill D203]

hi there,  putting a chainsaw engine in a boat.  problem is , runs great with the original fuel tank in situ,
 but only runs for a few seconds with new tank from  pmb.   got new pipes for flow and return,    can anyone  help.

OK What carb is it useing? Put some pics up and I will take a look for you. I need to see the tank/ carb hight. Dose your carb have a primer bowl fitted?

[triumphjon]

does the motor in its original use a gravity feed for the petrol ? where is your new tank in relation to the carb ? also have you changed the exhaust as back pressure from the exhaust to the engine can make a difference to it running properly .

[Bill D203]

Has the new fuel tank got a breather hole in it?

[50mm]

yes a breather hole is needed to allow the fule to move as trapped air will cause a vacuum!

best bet is off the tune pipe there should be a tube connector near the exit hole ( a little nipple) if not fit one! this tube is then connected to the breather hole,(also fitted with a nipple)  the force of the engines exhaust (back pressure) aids to pressurises the tank enough to push the fuel to the engine making it more efficient. This will solve your problem 

[Bill D203]

yes a breather hole is needed to allow the fule to move as trapped air will cause a vacuum!

best bet is off the tune pipe there should be a tube connector near the exit hole ( a little nipple) if not fit one! this tube is then connected to the breather hole,(also fitted with a nipple)  the force of the engines exhaust (back pressure) aids to pressurises the tank enough to push the fuel to the engine making it more efficient. This will solve your problem 

NO NO NO NO!!
DO NOT CONECT THE PRESSUE PIPE ON A PETROL TANK. It is OK on Nitro but a big no no on petrol.

[50mm]

i've had no issues in the past, maybe a different way or doing things your side of the world?

[pintheair]

thanks guys .old tank under engine, flow to primer then carb.   return to tank . no vent ,although green fitted bung on side.
new clunk tank  flow to primer ,return as before ,   tee off for vent on return  sorry about wait , computer at hone, boat at work, see what i do in tea breaks!




pipe,

[Bill D203]

OK Now I can see. I did the samething as you but i had to take out the primer bowl to get mine to run. It looks like a warborg carb. You may need to change it to a warborg 257 carb. However it will lift up petrol from a tank 3-4" below the carb. To prime it up, Pull the engine over slowly with finger over the carb then it should fire up OK. Now I see you still have the air filter on. Take it off! the inside of your boat will not be dusty as when it was a chain saw motor. This should short it out. Try and run it with just a supply pipe without the the return pipe. It will be OK to test.
I hope this helps.

[pintheair]

thanks bill , will try that tomorow, got a sneaky feeling might have the inlet and outlet pipes mixed up
at one point,  remind me,  top for fuel in?
 and thanks to all who answered,   every bit of advice is useful!!
that carb is by zami   

[Bill D203]

Looking at the pics fuel in on the bottom pipe.  The other thing there is a built in filter mesh on the inside of that carb. This can be seen if you remove the bottom plate which is held in place by 1 screw. It maybe worth looking at that!

[pintheair]

hi again, managed to solve my problems , thanks to you all.
it was so simple that i booted myself  , both flow  and return pipes have to be submerged in the tank !
just turned tank upside down so the return pipe was on the bottom and presto!   engine that runs again.
must be a syphoning system, 

 ps  got my next project lined up ,anyone tried this yet?