So I have a not so stock predator 212 that is dumping fuel out of the carb. The engine has a billet rod, billet flywheel, advanced timing, race prepped carb, 18lb valve springs, intake, and header exhaust. Engine runs great and strong. I’m running a Walbro pulse style fuel pump with it. I have cleaned the carb and I know the float is not sticking and that when closed the plunger works great. Last night we had our first big race (we started a little track at our family land) and out of 9 karts, 3 were running these same fuel pumps and all 3 were dumping fuel. Mine and 1 other engine were modified and the 3rd was stock except the gov was removed and was using the fuel pump. We are all new to this so excuse the ignorance...but is there something we don’t know about using a pulse pump with a predator engine? We are all fairly mechanically inclined but this one has us stumped. Is it possible that the small spring on the float needle isn’t strong enough to close the plunger under the pressure the pump is pumping fuel in??
Predator 212 carb dumping fuel.
- Thread starter Begarrett
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They all do it. Gopowersports in Keller Texas is working on a solution to the issue but haven’t quite got it right yet. Mine does the same thing.
On my other engine I ran a second line with a tee in the middle of the feed hose and ran it back to the tank and it helped as it acted like a return like a efi on a car uses.
On my other engine I ran a second line with a tee in the middle of the feed hose and ran it back to the tank and it helped as it acted like a return like a efi on a car uses.
I'm sure the needle valve can't handle the pressure. Mikuni carbs have different needle and seats for gravity fed setups and pulse fuel pump setups. You might want to see if the fuel tank is getting pressurized. After you shut the engine off take the gas cap off and see if there is pressure.
There isnt any pressure in the fuel tank as it is open vented. Good to know its s known issue. Sounds like its just what I thought. I had already got some 1/4” tee fittings and plan on trying that return line. I was figuring that would help releive some of that pressure from the pump. Also looked at the Mikuni carb. Not sure with my engine which would be the one to get. I am pushing somewhere between 12-15hp. Would the 22mm carb work? Or should i look at the 24? Also, will i be able to swap out the jet from my current carb to the mikuni? All i see stated is that they dont use mikuni jets so i assume my jet in the current predator carb will work? Any thoughts?
So much for that...talked to GoPowerSports. They informed me that they are NOT working on a solution and that they've never really had this problem on the stock predator carbs. He said they've seen it with the Mikuni carbs but not the stock predator ones. Talked to a few other shops and they said they hadn't seen this either. So I'm wondering if we all got a bad batch of predator carbs with our motors (we all did purchase from the same store at the same time).
JTSpeedDemon
2019 Build Off Winner!
That's what happens when ya buy stuff from China!
Sometimes there's just a bum engine.(or two, or three, or four....)
65ShelbyClone
Active member
Are you still using the stock tank on top of the engine? What fuel?
JTSpeedDemon
2019 Build Off Winner!
I gather that you also posted this question on KartFab.com as Brian.
Here's what he said on there in case you haven't seen his reply and also for other people wondering about a solution:
"Here is some background to help you understand why its dumping fuel. So the float itself can only push up so hard on the needle, and the needle pushes up on the needle seat to keep more gas from flowing into the bowl when the bowl is full. So you have a gravity fed system (stock carbs) that works great unless you either don’t get enough gravity fuel flow, or you have to mount the gas tank lower than the carb itself. In the instances where you dont get enough (or cant get any) fuel flow, that is where you need a pulsed fuel pump. The problem is that the pumps pulse pressure pushing the fuel into the bowl via the needle seat overcomes the pressure that the float and needle are applying to the seat. The fuel fills the bowl, and at the top of the bowl, you have a vent to atmosphere. The air vent now becomes a fuel vent and it looks like the carb is “leaking fuel” but in reality the carb is completely full of fuel, ruining your air fuel ratio, and you are blowing excess fuel out of the air vent that is supposed to help with optimal metering of fuel as well. So what to do? If you run a fuel pump, you MUST run a needle seat that is SMALLER than the stock one."
-Grant from KartFab.com
Hope this helps.
Here's what he said on there in case you haven't seen his reply and also for other people wondering about a solution:
"Here is some background to help you understand why its dumping fuel. So the float itself can only push up so hard on the needle, and the needle pushes up on the needle seat to keep more gas from flowing into the bowl when the bowl is full. So you have a gravity fed system (stock carbs) that works great unless you either don’t get enough gravity fuel flow, or you have to mount the gas tank lower than the carb itself. In the instances where you dont get enough (or cant get any) fuel flow, that is where you need a pulsed fuel pump. The problem is that the pumps pulse pressure pushing the fuel into the bowl via the needle seat overcomes the pressure that the float and needle are applying to the seat. The fuel fills the bowl, and at the top of the bowl, you have a vent to atmosphere. The air vent now becomes a fuel vent and it looks like the carb is “leaking fuel” but in reality the carb is completely full of fuel, ruining your air fuel ratio, and you are blowing excess fuel out of the air vent that is supposed to help with optimal metering of fuel as well. So what to do? If you run a fuel pump, you MUST run a needle seat that is SMALLER than the stock one."
-Grant from KartFab.com
Hope this helps.
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