My TaoTao TBR7 Mikuni Carburetor Jet Sizes

I moved up to the Nibbi Racing Carburetor, model PE30, and a common question is how to tune your carburetor for the TaoTao TBR7 (and Hawk 250). So being that my TaoTao TBR7 Mikuni carburetor jet sizes finally worked out, I would go over what I did and how others can relate to this.

Why I Need A TBR7 Carburetor Upgrade.

Oh, I do like the Nibbi Racing Carb( TBR7 Nibbi Carburetor Installation Instructions (With Hawk 250 info) ), although more expensive than the Mikuni Carb ( My TBR7’s Carburetor Upgrade! (Mikuni) ) and the Nibbi PE30 is finicky with tuning the jets. However, I did get a real boost out of the Mikuni carb when I upgraded from the stock TaoTao TBR7 carburetor. Just an FYI.

Altitude Is Key For Carburetor Jet Sizes.

I Live In Eastern Pennsylvania.

I am told that altitude changes oxygen concentration for the same volume of air running through the carburetor. Which can affect the ideal fuel/air(‘oxygen’) ratio.

When you go higher in altitude, you have to run your carburetor with less fuel flow due to less available oxygen molecules for the volume of air passing through the carburetor, which means smaller carburetor jets.

Conversely, at lower altitudes, the amount of available oxygen molecules increases for the same amount of air volume passing through the carburetor. So to maintain the ideal fuel/air(“oxygen”) ratio, you must increase the fuel amount entering the engine intake—therefore, larger carburetor jets are needed.

Pennsylvania has mountains, farmlands, and even some waterfront areas, so saying I’m from Pennsylvania and mostly ride in Pa is not very helpful for people copying the Mikuni carb settings I use. I have to give you the elevation so you can compare apples to apples. I ride primarily around the Lehigh Valley area of Pa, venturing into the Bucks County and NJ areas with my TaoTao TBR7 motorcycle.  

I have not played much in the Poconos area, which is an actual altitude increase, so I can’t give you information about riding at those altitudes. However, I can only guess the motorcycle would have run a little rich.

I would have had to go down a size with my jets to operate my carburetor correctly. But only if I noticed a real power change. I figure the Mikuni carb can tolerate some altitude changes before needing adjustment. However, going to the Nibbi carb now, I will not be able to test this.

So guessing to give you an average elevation I operate my TBR7 motorcycle, I would imagine 360 feet above sea level, per the Wikipedia page about Bethlehem, Pa. https://en.wikipedia.org/wiki/Bethlehem,_Pennsylvania

My Final Mikuni Carburetor Jet Settings

These are the last settings I made to the carb jets before I upgraded to the Racing Nibbi Carb (PE30): TBR7 Nibbi Carburetor Installation Instructions (W/ Hawk 250 info).

My VM-26 Carburetor Fuel/Air Screw Setting:

• The Fuel/Air screw controls fuel flow at idle.

First the fuel/air screw is not a jet, but part of the idle circuit. 

Note: It’s a fuel/air screw on the carburetor’s downstream side and meters fuel flow. If the screw were on the upstream side, it would meter airflow to maintain a proper idle ratio.  

My fuel/air screw is turned 1, and a half (1.5) turns open from lightly closed.  

With this setting, I don’t recall any excessive popping noises when decelerating or idling the motorcycle.

My Carburetor Pilot Jet, or Idle Jet Setting:

• Pilot Jet usually controls fuel flow at about 0%-25% throttle open.

Again, no popping noises during deceleration or idling, so this size worked for me. I use a Mikuni Jet Size of 20

Others have said a 20 is too small for the TBR7, but it worked for me.

My Motorcycle Carburetor Needle Jet Setting:

• Needle Jet Setting controls fuel flow at about 25-75% throttle position.

Some would argue that the needle valve isn’t a jet since it has an opening/orifice, but it controls fuel flow and is adjustable. So for the sake of argument, I’ll give you my setting.

There are five-needle clip positions; I am in the middle clip. The mid-position on the needle, and it was the stock needle that came with my Mikuni carb.

My Carburetor Main Jet Setting:

• The Main Jet controls fuel flow at about 75-100% throttle open position.

I played around with this and tested larger sizes, but I didn’t particularly appreciate how ‘white’ the spark plug looked when I checked. So I settled for a Mikuni main jet size of 110.

Motorcycle Carburetor Jet Settings Weirdness.

Many motorcycle carbs, Mikuni not excluded, have settings that aren’t precisely copy-able. 

You can have a room full of the same type of motorcycles, all having the same kind of carburetors, but some might not have the exact size of the group. It happens, so resizing the carb jets and testing the performance/operation of the motorcycle is the best way to find out what jet size you need. 

This post is only stating what worked for me with a TaoTao TBR7 motorcycle, using the stock engine( TaoTao TBR7 Review & Specs ), foam air filter( TBR7 Air Filter Pod Replacement ), aftermarket exhaust( TaoTao TBR7 Exhaust Upgrade ), and riding almost full throttle all the time to keep the RPMs up for quick acceleration.

It might be much to ride with high RPMs, but traffic can get stupid, and having as much acceleration to get out of the way has kept me alive.

Oh, high RPMs can affect the motorcycle engine temperature, so I also installed an engine oil cooler ( Oil Cooler Installation For My TaoTao TBR7 Motorcycle ).

I hope this helps, and if you have feedback about the jet sizes you are running in your Mikuni carburetor, please do so. Also, include what altitudes you are operating your motorcycle (A Chonda) at and your riding style(road, off-road, etc.).

Ride Safe, Ride Fun!

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