lack of fuel

Posts: 10

Well, I've been tinkering too much. I've finally installed a performance carb on the roketa 150 (gk28) we have. Getting it to fit was a challenge. I had to move the carb 7" from the intake manifold using the redneck intake. Then I mated it to a Uni filter. The buggy runs awesome until you hit a high speed run for any length of time. In about 15 seconds the float bowl is out of fuel and the buggy bogs down.

I've checked the vacuum line to the pump, seems normal. Filter isn't clogged. No leaks (vacuum or fuel). If you let the buggy idle the bowl fills up and you can do another short run. If you run and vary the throttle (low speed/high speed) the delivery keeps up.

So, what are my next steps? I'm thinking I could install an electric fuel pump? Is it jet related?

I do have the stock exhaust on still....that purchase needs the wife's approval.

Thanks everyone!

David

Posts: 1868

Your intake run is too long and causing these problems. You need to to use a riser on the intake elbow or reposition that carburetor into the original spot (many replace the top long engine mount bolt with two small ones to gain clearance).

Posts: 10

Why is it too long though? What is the cause? Is it because the distance decreases the vacuum pressure for the fuel pump?

I would have replaced the mounting bolt with two small ones but I hit on the casing and the air shroud/ducts so I have multiple issues. Stupid carb does not just "bolt on" as I expected.

I'll get in touch with BigE to get a carb spacer... But I still want to understand the cause.

Posts: 648

that new carb is using fuel faster than the stock gas line can deliver. It's a common problem when going to aftermarket stuff. upgrade the gas line to a larger size and use a good quality high volume inline filter.

Posts: 1868

Air and fuel atomize in the carburetor. If the path is too far to the combustion chamber, the fuel starts to reform into droplets. You can adjust that runner length to optimize a particular RPM range, but I do not know the formula or what other parameters (intake velocity, cfm, etc.) are required to get your length.