Jetting help. Gy6 engine in yerf dog kart.

N

Nathannewbie

Member
Hi all,
Thx in advance for the help. I recently bought a yerf dog spider box go kart, and I replaced the carb and welded just a straight header on because the exhaust was snapped off. It doesn’t want to start, idles like crap, and after it warms up it bogs in like the 1/8 through 1/2 throttle range. I’m thinking jetting but what would you guys recommend?
 
Did you compare the jet in the new carb to the one in the original carb? Did you set the float height? I have had several of the cheap imported 4 wheelers come thru the shop with the GY6 engines, and have bought replacement carbs for them. They are horribly inconsistent, the casting quality is terrible. First thing, check the float height and adjust it so the needle valve shuts off when the float is level with the carb bowl. Then determine if it is starving for fuel or running too rich. You can do that by placing your hand over the carb inlet and blocking some of the air off when it starts to bog, or by pulling up slightly on the choke when it starts to bog. If it accelerates it is too lean, if it bogs worse it is getting too much fuel.
 
IF its a Gy6 it probably has a constant velocity carb (diaphragm slide/spring mounted on the top), these are sensitive to proper air cleaner with some resistance for the slide to function properly. Are you running stock air filter? If not, or no air filter, it will mess up things bad.
 
Hey guys thanks for the reply's. The new carb seems fine other than it just doesnt seem jetted right. It runs great at full throttle just doesnt idle or low rpm well.
On the air filter, idk what to get cause I pulled the air filter off today and it is a piece of **** because the carb body was COVERED in dirt. Any idea what filter? Or is it cause I didnt oil the one that it has on it?

It will be hard to check if its rich or lean at idle since it has an electric choke, but I do know its running rich cause it was throwing fire out the header.
 
I'm not sure I can agree with you on the engine being rich at an idol. You say it hesitates when you go WOT, that indicates lean. Try partially choking the carburetor and going WOT, does it still hesitate?
 
Also, if anyone could tell me which jets are which... theres a flat head small jet which sits in a 6 mill jet or emulsion tube or something and then theres another jet which is pretty small but idk which is what.
 
"New carburetor" what does that mean. Stock carburetor? Can you post a picture? Does it have replaceable jets?
Do you have a picture of the kart? You replaced the exhaust, from what to what?
We're throwing darts in a room with no lights, we need more help!
 
alvin l nunley said:
"New carburetor" what does that mean. Stock carburetor? Can you post a picture? Does it have replaceable jets?
Do you have a picture of the kart? You replaced the exhaust, from what to what?
We're throwing darts in a room with no lights, we need more help!
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Sorry, aftermarket. Post a pic of inside or of the whole carb. Yes, it has replaceable jets.
Do you want a pic of the exhaust too? It just was an exhaust and now its a straight header.
 
I know for sure you can swap out the pilot jet, the main jet, and whatever the main jet sits in.
Is there supposed to be another jet?
 
"Another jet?" I have no idea, but we can work with those 2.

Was there a muffler on the exhaust before?

Do you have any way to measure the jet sizes? Within .001"? Do you have a source for new jets of different sizes? Knowing what the jet sizes are now will give me a clue as to how big you need to go with the new jets. Most machine shops will have pin gauges to measure the hole size if you don't. Right now were throwing darts in the dark. lol
 
alvin l nunley said:
"Another jet?" I have no idea, but we can work with those 2.

Was there a muffler on the exhaust before?

Do you have any way to measure the jet sizes? Within .001"? Do you have a source for new jets of different sizes? Knowing what the jet sizes are now will give me a clue as to how big you need to go with the new jets. Most machine shops will have pin gauges to measure the hole size if you don't. Right now were throwing darts in the dark. lol
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I meant, Idk if there is only a main and pilot jet or if there is supposed to be more.

Yes, there was a muffler before. So it runs ok on idle now that I changed the filter to a bigger one but now it SUCKS at almost the rest of the throttle. Im thinking I definitely need a bigger main.

I don't have a way to measure them. I did order a jet kit from amazon thats supposed to be here today. They do have sizes on them and the main is like a 103... not sure on the pilot is 34.

Also.... both the air filters I tried on there are sucking dirt so I think its the intake piece that is between the air filter and carb... and ideas on what to use? Radiator hose is EXPENSIVE.
 
Did you or should you oil them? Red Green used duct tape . Silicone works .
Like Al said we know you have a problem , the description just doesn't pin point it .
Put a nylon stocking over the air filter or some type of foam .
 
flattop1 said:
Did you or should you oil them? Red Green used duct tape . Silicone works .
Like Al said we know you have a problem , the description just doesn't pin point it .
Put a nylon stocking over the air filter or some type of foam .
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I dont know if they are supposed to be oiled

Well... idk what im supposed to pinpoint. It has a new carb. Header, without exhaust so its higher flow now..... just need better jetting I guess
 
Nathannewbie said:
I meant, Idk if there is only a main and pilot jet or if there is supposed to be more.

Yes, there was a muffler before. So it runs ok on idle now that I changed the filter to a bigger one but now it SUCKS at almost the rest of the throttle. Im thinking I definitely need a bigger main.

I don't have a way to measure them. I did order a jet kit from amazon thats supposed to be here today. They do have sizes on them and the main is like a 103... not sure on the pilot is 34.

Also.... both the air filters I tried on there are sucking dirt so I think its the intake piece that is between the air filter and carb... and ideas on what to use? Radiator hose is EXPENSIVE.
Click to expand...
Hi I'm fine and you will all out and will her and will you and well and will you go all in and in and in and no is an is a factor in her is she I like what you are about you are back in the is a and and I and thought about you can be you are you and you very and he will round of study in an and you are what.001" on the high-speed jet is a bout a plus/minus change of 2%. On the low-speed it's about 6%. Obviously that means the percentage difference in flow. I would work on the low-speed jet first. .001" bigger at a time. Obviously a 2% change in the big jet represents a lot more flow than 6% in the low-speed jet. Pictures would help!
 
alvin l nunley said:
Hi I'm fine and you will all out and will her and will you and well and will you go all in and in and in and no is an is a factor in her is she I like what you are about you are back in the is a and and I and thought about you can be you are you and you very and he will round of study in an and you are what.001" on the high-speed jet is a bout a plus/minus change of 2%. On the low-speed it's about 6%. Obviously that means the percentage difference in flow. I would work on the low-speed jet first. .001" bigger at a time. Obviously a 2% change in the big jet represents a lot more flow than 6% in the low-speed jet. Pictures would help!
Click to expand...
Can you rewrite that? I have no clue what you said. Confusing
 
Last edited by a moderator:
Nathannewbie said:
I dont know if they are supposed to be oiled

Well... idk what im supposed to pinpoint. It has a new carb. Header, without exhaust so its higher flow now..... just need better jetting I guess
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You say your getting dirt in the carb .
So the Question is from where ?
The connection or the filter itself . Generally paper does not get oiled .
The others do .
 
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