March 29, 2019 Geoff Warner

Carburetor Tuning 101

Carburetors are a thing of the past for most internal combustion engines these days. Pretty much all late model bikes, cars, even some golf carts come from the factory with EFI (electronic fuel injection).

Unfortunately, small engines haven't quite caught up to technology, and this is simply because of pressure to keep costs down. Lets be honest, if people would pay $3000 for a big block kit, all of our engines would come EFI...but that's just not the reality.

That being said, our engines are stuck in 1970 with their archaic 3 circuit - single barrel carburetors, yet still have to meet strict EPA emissions standards to be allowed into the country. In order to accomplish meeting emissions regulations, the carbs on our engines have to be run very lean (not enough fuel).

If you are having drivability issues, popping/backfiring issues, or hard starting issues..this is simply just a case of a carb in poor tune. We don't want to sell them this way, but we are required to by federal law! This isn't just our product, any new engine you buy from any vendor (Harbor Freight, Home Depot, etc) is going to have the exact same issue in a golf cart/automotive application.

So how do I fix this issue?

Simple, you have to "re-jet" your carb. The easiest way to do this is to actually drill out your jets, one size at a time, until the engine runs the way it should. You need to be careful not to go too big or the engine will run rich (too much fuel) and you will get terrible gas mileage and foul spark plugs. To get started, you will want to get your hands on a "micro drill bit set", they can usually be found at Harbor Freight or on eBay for under $10 shipped and will include a hand pin vise :

Micro Drill Bit Set

In most cases, the only jet that will need to be enlarged is the "Low Speed/Idle" jet. Its rare that the mid or high speed jets will need to be oversized. The pictures below will show you how to get to your jets:

Idle Jet

The first thing you will want to do is identify the current jet size by inserting the best fitting drill bit into the existing jet orifice. Once you have that, open the hole up to the next drill size and test the engine.

Remember, the engine must be at full operating temperature before tuning. Do not try to tune your carb on a cold engine. A properly tuned carb will start alot easier as well!

Repeat the above process until the cart is running like it should. If you go too big, you will need to buy another jet and start over.

ADVANCED TUNING:

If you want to experiment with the other circuits of the carb (Mid & High), you will need to remove the carb from the engine, drain and remove the fuel bowl and unscrew the jets on the bottom side of the carb. The Main or High Speed Jet is in the direct center of the carb, the Mid Range jet is offset from the center. Refer to the picture below: