Engine idles fine, but dies when rev up :/

[AndyAndyAndy]

Engine idles fine. But dies when rev up. At high revs sounds like is firing only every X combustion stroke.

I thought it might be fuel delivery issue. I checked from tank to carb. No problem. I bough new carburetor. Nothing changed. I also checked timing. I checked valve lash.

See for yourself when I try to rev up:

 

[Zheking]

I have the same problem on my coleman except it completely dies. Following to see what replies you get.

 

[madprofessor]

Go to "Gokart Discussion" section of this forum. Search ""SchizoBallz" kart build started". 2nd page, think it's Feb.25 post, second one.
It's a discussion about double fuel filtering, transparent fuel filters, transparent tubing as a fuel gauge, etc.
When you "check" a carb, fuel line, whatever, and say "no problem", you need to really know that. My cone-shaped transparent fuel filters keep an air pocket for some reason, love that. Makes it really clear to see what the fuel is doing.
Simple substitute is transparent fuel tubing, where swoops and such dips will show it if you're getting air in with the fuel. At the least you need a way to check for fuel (while motor running) right at the carb.
Video says you're leaning it to death. Lots more air, no more fuel. If it ever sat a long time then fuel varnished everything, including the main jet. That's a microscopic hole, and any varnish at all is all it takes to shrink that hole to idle revs only. If you moved the jet over to the new carb, well....................

 

[DukeKL]

Go to "Gokart Discussion" section of this forum. Search ""SchizoBallz" kart build started". 2nd page, think it's Feb.25 post, second one.
It's a discussion about double fuel filtering, transparent fuel filters, transparent tubing as a fuel gauge, etc.
When you "check" a carb, fuel line, whatever, and say "no problem", you need to really know that. My cone-shaped transparent fuel filters keep an air pocket for some reason, love that. Makes it really clear to see what the fuel is doing.
Simple substitute is transparent fuel tubing, where swoops and such dips will show it if you're getting air in with the fuel. At the least you need a way to check for fuel (while motor running) right at the carb.
Video says you're leaning it to death. Lots more air, no more fuel. If it ever sat a long time then fuel varnished everything, including the main jet. That's a microscopic hole, and any varnish at all is all it takes to shrink that hole to idle revs only. If you moved the jet over to the new carb, well....................

My buddy might need to see that video for his incoming Coleman project. We're finishing the installation of the brake pads and hd wheels on his truck when he mentioned the Coleman having a revving issue.

 

[OPmini]

Try cleaning the carb (or getting a new one), adjusting the air / fuel mix screw, jetting the carb right, and adjusting the valves.

 

[DukeKL]

Try cleaning the carb (or getting a new one), adjusting the air / fuel mix screw, jetting the carb right, and adjusting the valves.

That's what we will do first.

 

[Budget GoKart]

carb adjustment is important your needle in the slide if not correct can cause many running issues expeccially with china knock off motors ive dealt with several of them and just got a free 125 tao tao four wheeler that doesnt run and iu will have to fix it as well