Fuel pump on a Predator 420 install?

[JD466US]

I am having what I believe is a fuel pump issue with my 420 install. I did the predator 420 swap using the Vegas carts kit on a 1993 Marathon. On the engine I did the govenor removal, installed the heavier valve springs, header, and rejetted the stock carburetor. Well it runs great except if I run at WOT for a little ways. It seems to me that the fuel pump isn't keeping up with the amount of fuel the engine needs and its draining the bowl on the carb. It will start sputtering after a short distance run at wot. If I let off, feather the throttle a little it catches back up and runs fine. It also runs fine at 1/2 throttle. I decided to change out the carb with the 24mm bored carb and still have the same issue though the throttle response is much smoother. I am running the Walbro fuel pump which I bought last fall when I built the cart. So my question is has anybody else run into this issue? Is anybody running a electric fuel pump? I have one of the small Mr. Gasket electric pumps I have thought about using. Any thoughts or opinions would be greatly appreciated

[raydhd]

I run a B&S Mikuni #808656 on my heavily modified VC 460. With this I run a restricted return like. This was the only set up that worked for me on a very hot day running for miles @ 5000 rpms +. I have on my sled engine powered HD cart a Holley low pressure electric # 12-426. Getting the right fuel delivery to the clone engines has to be right. The more modded the engine the more critical it becomes.

[Shepard]

Originally Posted by JD466US

I am having what I believe is a fuel pump issue with my 420 install. I did the predator 420 swap using the Vegas carts kit on a 1993 Marathon. On the engine I did the govenor removal, installed the heavier valve springs, header, and rejetted the stock carburetor. Well it runs great except if I run at WOT for a little ways. It seems to me that the fuel pump isn't keeping up with the amount of fuel the engine needs and its draining the bowl on the carb. It will start sputtering after a short distance run at wot. If I let off, feather the throttle a little it catches back up and runs fine. It also runs fine at 1/2 throttle. I decided to change out the carb with the 24mm bored carb and still have the same issue though the throttle response is much smoother. I am running the Walbro fuel pump which I bought last fall when I built the cart. So my question is has anybody else run into this issue? Is anybody running a electric fuel pump? I have one of the small Mr. Gasket electric pumps I have thought about using. Any thoughts or opinions would be greatly appreciated

If you have the pulse line hooked up to the carb insulator plate you'll loose signal at WOT and run out of fuel. You can use the crankcase pulse to run the fuel pump but will need to have a simple return fuel line so the carb doesn't flood and leak. None of these carburetors are made for a fuel pump - there made for gravity feed. This is the major reason they run out of fuel or dribble gas. I haven't had a single fuel issue since I changed over to gravity feed fueling.

[KRAZYMATT]

Open the jet up more. My predator 420 did the same thing, I changed carbs, fuel lines filters pumps even put electric pump on at 1 point still did same ****. Opened the jet up more and didn’t have the problems anymore. I went back to the factory club car pulse pump. Pulse line off the carb insulator and haven’t had any issues. Either open jet up with torch tip cleaners or buy jet kit for Honda gx390. Drop the bowl screw the factory jet out and install the larger one. I don’t know the size of the factory jet but on my predator 420cc I went to a #44.

[slonomo]

Originally Posted by raydhd

I run a B&S Mikuni #808656 on my heavily modified VC 460. With this I run a restricted return like. This was the only set up that worked for me on a very hot day running for miles @ 5000 rpms +. I have on my sled engine powered HD cart a Holley low pressure electric # 12-426. Getting the right fuel delivery to the clone engines has to be right. The more modded the engine the more critical it becomes.

I run the same setup.

[slonomo]

Originally Posted by Shepard

If you have the pulse line hooked up to the carb insulator plate you'll loose signal at WOT and run out of fuel. You can use the crankcase pulse to run the fuel pump but will need to have a simple return fuel line so the carb doesn't flood and leak. None of these carburetors are made for a fuel pump - there made for gravity feed. This is the major reason they run out of fuel or dribble gas. I haven't had a single fuel issue since I changed over to gravity feed fueling.

You can sometimes get a new needle valve that is supposed to be for pressure feed. But, as Shepard says, gravity works best on these carbs. I didn't have a way to do that, so I ran the return line. Worked great that way. I ran mine off the intake pulse fitting and never had a problem.

[BIKERMIKEYBLACK]

I run both my engines off the valve cover with no problem 420 and Vanguard

[slonomo]

Originally Posted by BIKERMIKEYBLACK

I run both my engines off the valve cover with no problem 420 and Vanguard

I think all Vanguards use the valve cover pulse method from the factory.

[Field6565]

I had my clone pulse coming off the isolator and it never worked right. Always running out of gas. Drove me nuts. Finally tapped into the valve cover and never had a problem.