Clone Carb Tuning – Emulsion Tubes vs Jets

GX200 Clone Carb

GX200 Clone CarbWhen I first started working on the clone motors, especially the carbs, there seemed to be a limit on what you can change for tuning. Primary air jet setting is absolutely necessary for idle and low speed. Even a drop of oil in the primary air jet will ruin your day, and it happens. I use a .0225 primary jet for my modifies.

With the stock clone carb we are only given jets and emulsion tubes correct? Different jet sizes .038 thru .043 are used for both the smaller gx200 and the gx270 carb. All the tubes and jets are interchangeable. The real tuning is in the emulsion tubes. Most commonly, the 140 emulsion tube is offered by most companies selling parts. What’s the big difference between the 140 and stock? So far I have found 6 different tubes. Different size holes and at different locations on the tube. The measured volumes of all these holes varies very little. The big differences is in the inside diameter (id) of the tubes. They range from .063 thru .087. The 140 tube is .068, only the second largest. So if you solder holes and make the tubes close to the same except for the id, you can tune your head temp by ten degrees. Add spark plugs and a little air density information and your good to go.

Spark plugs can allow your engine to run at different temperatures and are also good for tuning. We all live in different climates so your tuning may differ from my tuning out here in the middle of California.

So far I haven’t seen a carb, Tillotson or stock, that couldn’t be helped with enlarging the mid-range fuel delivery. Good for 3 tenths or a second off your laptime with a stock carb.

I enjoy getting the most of what is available before I buy what everyone else has and I like using my mind and experiences rather than sticking on a Mikuni or Tillotson.

What are your experiences with stock carb tuning? Share your thoughts in the comments box below.

This post was written by Ken Hill, a karting engine builder with over 25 years in the industry.

Author: Jerad Hill

Husband, father, business owner.

2 thoughts on “Clone Carb Tuning – Emulsion Tubes vs Jets”

  1. Good morning, was intersted in the clone crburetor since i’ve just purchased my first red clone. My son has been racing for the past 8 years and is now 15yoa. We have not won much but have shown up and tryed to stay consistent over the years. With all the losses and very few wins….about 12, his love of the sport has deminished. I’m not an engine builder, just a dad. I have learned alot about the importance of all the parts from listenig and learning along the way. If there’s any information you can share to help me save my sons enjoyment it wold be appreciated. He now runs adult animal and adult clone 350/375. We cna never make it past mid pack and the shop guys are always 2 or 3 tenths faster somehow. Love the sport but can’t put him up front enough to keep the spark lit. We will try this last season and see what happens from there.

    1. Good after noon, it takes alot of money to run with the adult 350/375 they got alot of money in there carts rebuild the carb and the engine with after market parts

Leave a Reply

Your email address will not be published. Required fields are marked *