I Need A TBR7 Carburetor Upgrade.

Let me say one thing about the TBR7: I plan many upgrades that don’t make the TBR7 a bad motorcycle choice. I enjoy tinkering and doing upgrades that turn a mediocre motorcycle into a better, customized motorcycle. Thank you, and now on to my next project. TaoTao appears to have focused its designed power output as very low and controllable by the rider. This goal is evident with their stock carburetor. The motorcycle sips fuel and has very modest power output. Often the TBR7 “bogs” down when fully opening the throttle and reaching the top end of power output very soon after shifting gears. With all these performance issues, I feel my TaoTao TBR7 motorcycle needs this upgrade.

Now the past reasons for a carburetor upgrade are kind of subjective. I have been quoted many times as wanting more POWER! However, I found proof that the motorcycle was low-powered by a poor overall design but created to limit the power intentionally. When I changed the spark plug ( Spark Plug Upgrade ), the electrode area was white-ish.

Disclaimer: I plan to write this post outlining what ran through my head as I tried to understand why a spark plug’s color leads to me wanting to upgrade the carburetor. Bear with me; I am no expert, just learning as I go along.

What Does Spark Plug Color Mean for Carburetor Needs?

Having a spark plug with white-ish deposits indicates a lean operating environment in the engine’s combustion chamber. Simply put, this spark plug coloration indicates too much air for the amount of fuel entering the chamber or too little fuel for the amount of air entering the chamber.

Let me put this even more straightforward; the motorcycle wants more fuel! More fuel quickly translates to more POWER in my head. I could see a performance boost in the TBR7.

To see what I’m talking about, look at the TaoTao stock spark plug that came with my TBR7. I only ran it for a short period before upgrading it.

TBR7 Stock Spark Plug Electrode End.
Stock TBR7 Spark Plug.

What Is Planned, and How Is The Carburetor Involved?

Her I go, after some web and forums searches, this is what I learned. The carburetor’s internal components control the flow of fuel. There are internal, changeable jets(two for the TBR7, I found out) that control the amount of fuel that gets dawned into the air stream throttled by the, ah, throttle. An idle jet controls the lower power range fuel flow, basically the idle speed. As the throttle is opened, the airflow increased, a needle valve repositions itself further open and increases fuel flow through the throttle body. The carburetor needle seems to control the fuel flow with air, from low power range up to near max. Once the carburetor needle is fully open, the most restrictive fuel flow control device is the Main Jet.

So at low power, throttle closed – idle jet.

At mid-power range – needle valve positioning.

At High-power range – Main Jet Size(hole/orifice size).

What Is It I Want To Upgrade In the Carburetor?

The goals are to leave the idle jet the same and not mess with the needle valve, so my goal is to increase the Main Jet size. This increase in Main Jet size will increase fuel flow when the demand throttle is wide open, which is the greatest.

Can I Tune The Stock Carburetor, Instead Of Upgrading?

Any easy answer: YES, with some elbow grease. The stock carburetor has no exposed screws to disassemble the carburetor and change the jets. A quick web search will find many people showing how to ‘hack’ (literal hacksaw) the carburetor into having screws. I looked at the steps and found it created many metal filings, and I am fearful I will contaminate the engine or turn the stock carbonate into garbage. Ordering a carburetor upgrade from Amazon is too easy. But, have to remember to order appropriately sized jets with the carburetor too.

So Go The Easy Route To Upgrade The TBR7’s Carburetor?

I have watched the research, learned from people who upgraded both the TBR7 and the Hawk 250(it seems both motorcycles have the same type of carburetor ), and found ordering a new carburetor and jet kit makes too much sense.

What Parts Did I Order?

1-The Carburetor, A VM26 Mikuni Carburetor.

2-A Jet Kit to go with the new carburetor.

So, What Is Next?

I wait for the new carburetor and jets to arrive and set aside to upgrade my TBR7’s carburetor. In the meantime, I plan to continue riding the TBR7 and break it in. I’m sure a light-bulb went off in a couple of people’s heads. Breaking in? Throttle wide-open? Yes, not suppose to do it, but curiosity overtook me. I did, and the TBR7 basically bogged and almost stalled. Not going full throttle till after a proper break-in period and the carburetor is upgraded.

Check back later, and I will have a follow-up post to this post when I complete the upgrade.

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TBR7 Upgrades

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