Please help

[New Jack]

I purchased a 212 Predator Hemi brand new. It ran great and gave me no problems through the break in process and everything. We had a storm here and it sat up for a couple of weeks. I put fresh fuel in the tank fired it up to find it idling rough and it would only run with the choke on. I removed the carb cleaned it and put in a new plug, installed a performance air filter on it and ran a remote fuel tank with a fuel pump. It will start up fine with the choke on and run for a few minutes with the choke on and then stall, after that its hard to start can someone please help me?

 

[mckutzy]

Hello and welcome...
These are a gravity fed engine they dont need a pump... unless the tank is under the level of the carb(like a racing gokart)...
With a new performance filter you typically need to rejet to accommodate the more free flowing air...

After unbolting and removing a carb, sometime there might be an air leak with one of the gaskets or the insulator plate might be cracked... that will cause starting problems...

Unless the motor was submerged itll handle almost anything you can trow at it... these are industrial engines....

 

[bob58o]

What he said^. Just took me longer to type.

Air Filter only? No exhaust upgrade?
The stock exhaust is probably more restrictive than the stock air filter.
I'm not sure you will need to rejet the carb if you only do the air filter and not the exhaust. You might, but I'm not sure. Most do both intake and exhaust together. Then that definitely requires rejetting.

How did you clean the carb? Did you take it completely apart and poke out all the holes with thin wire? If you didn't poke each hole in the emulsion tube and also poke both jets, you didn't really clean it. If you did, you can try to clean it again.

These carbs are designed to be gravity fed. The pressure from a pump is often too much for these stock carbs. Many people run a "T" off of the fuel pump outlet. One line going to the carb. Other line going back into the fuel tank.

Also you can check for air leaks around the intake. While it is running spay carb cleaner or starting fluid around the intake gaskets and carb insulator (between the carb and cylinder head). Avoid spraying near the filter. Listen for a change in RPMs. If the engine speed changes when you spray, then it indicates a leak.

Hope some of this helps.

 

[New Jack]

I just installed one of these headers today RLV5438C. what size jet would you recommend using to rejet the carb? It has been running fine with the stock jet with the bigger intake filter, but I'll tyr rejetting it. I,ve also read something about the motor doesn't give enough pressure to run a fuel pump. And yes the tank is under the steering wheel the Predator is on a Hasse Blizzard chassis.

 

[Noseoil]

Try a 36 jet. Did you clean the idle jet? It sits under the black plastic screw head, it's a small jet you have to pop out after removing the screw, very fine wire to clean & make it idle properly.

 

[bob58o]

With the new exhaust, you WILL NEED to rejet. 0.036" - 0.039".

You can get a micro drill bit set and incrementally increase the size of the jets.
https://www.widgetsupply.com/produc...kXfMQhJJhj2KVCNmPQoM4BTiTJNMqGAgaAiISEALw_wcB
Bits #61-#80
0.0135" to 0.039"

That will be good for both the idle and main jets, or you can buy a few main jets in the 0.036" - 0.039" range.

You could probably drill the idle to around 0.018". Many just do the main jet and leave the idle stock. So it is not absolutely necessary, but going up a size or two shouldn't hurt.

The problem with the pump is that the float needle and seat are not designed for the pressure of the pump. Gravity provides less than 1 psi. Pumps provide 3-5 psi.

The float should rise and seat the needle. That should stop the gas from entering the fuel bowl. With the stock needle and seat, the pressure from the pump will force the fuel passed the needle and seat. The carb will flood. You will need to change the needle/seat for use will a fuel pump (don't think it is an option with stock carbs) or add a return line to the tank. I used a fuel shut off valve on the return line to regulate the pressure to the carb. Open the return valve all the way to reduce fuel to the carb to a minimum. Shut the return valve to maximize fuel flow to the carb. I have heard of people using a pump with a stock carb and no return line, but I don't recommend it.

And can't stress enough to make sure all the little holes in the carb have been cleared and cleaned out.

And to make sure there aren't leaks.
https://www.youtube.com/watch?v=kMw91fiIXNc
https://www.youtube.com/watch?v=tlRZitBposI