SKU: 50561105411

Ultimate Racing MXR .21 Nitro Racing Engine (Ceramic) Combo w/2142 Pipe & Header

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Description

Ultimate Racing MXR .21 Nitro Racing Engine (Ceramic) Combo w/2142 Pipe & HeaderThis is the Ultimate MXR Ceramic 3 Transfer . 21 Competition Engine. Like its predecessor the MXS, this engine is manufactured by the prestigious Japanese brand O. S. Engines, in this case based on their square stroke Speed B21 engine. Apart from the modifications that the MXS already had, such as the crankshaft and back plate, the sleeve of the MXR has been modified, modifying the ports to be able to vary the inlet and exhaust timing. The inner head

 

This is the Ultimate MXR Ceramic 3 Transfer .21 Competition Engine. Like its predecessor the MXS, this engine is manufactured by the prestigious Japanese brand O.S. Engines, in this case based on their square stroke Speed B21 engine. Apart from the modifications that the MXS already had, such as the crankshaft and back plate, the sleeve of the MXR has been modified, modifying the ports to be able to vary the inlet and exhaust timing. The inner head has also been modified and includes the innovative FlowMax venturi to improve performance, more specifically, to achieve greater power without compromising fuel consumption.

With this engine you will have a really good power band with a ton of usable power. It has a smooth bottom end which worked well on the bumpy track and then has a lot of mid-range pop and feel to it. It is one of the best idling engines you can find on the market.

COOLING HEAD

The MXR is equipped with the same cooling head as its predecessors (MXS, MTS). This 8-fin cooling head has a very low center of gravity and has been designed to focus most of the airflow directly to the glow plug. By cooling the glow plug we get a more stable carburetion and idle.

CARBURETOR

Once again, the MXR comes with the 21 J3 carburetor. Unlike the original OS carburetor, its high-speed needle holder was redesigned for a better refrigeration of the fuel flow into the carburetor, lowering the temp of the carb, and consequently it is more stable with a great idle stability, improves fuel mileage and overall engine performance.

Besides this, the uniball joint of the carb slide was also modified with two stoppers instead of one. With this new modified design, you can easier adjust the angle of the uniball joint without having to disassemble the engine.

This carb offers a higher accuracy tuning, a very interesting advantage to experienced drivers.

BACKPLATE

Same as in the MXS, the MXR backplate has been modified. The backplate is CNC machined and made of 7075-T6 Swiss Aluminum. It has been milled to improve the gas flow going to the piston and improving engine efficiency and performance.

Thanks to its design, you can remove the backplate without damaging the conrod even when it is on its lower position (PMI). The lateral grooves allow to easily remove the backplate without having to use any tool that can damage it.

CRANKSHAFT

The crankshaft of the MXR is an evolution of the DLC B2102 but with two balanced tungsten in order to increase the inertia to rotation.

BEARINGS

The MXR comes with the original OS ceramic bearing in the rear and Ultimate Racing steel double sealed in the front.

VENTURI

The MXR comes with the 6.5mm Ultimate Racing FLOWMAX venturi. With an innovative design, longer than the standard O.S. venturis and wider at the base, unlike all others, makes the inferior part of the venturi and the carburetor have exactly the same diameter. This new geometry improves fluid dynamics, providing extra power that allows the use of smaller venturis without decreasing power, and as a consequence improves fuel mileage.

SLEEVE AND PISTON

Starting from the great base of the MXS, the sleeve of the MXR has been modified, modifying the ports to be able to vary the inlet and exhaust timing to achieve more power without compromising fuel consumption.

The sleeve with 3 inlet port and an exhaust port guarantees a low fuel consumption with a very high but smooth and linear power.

Both, the sleeve and piston are made from a high strength aluminum bar to improve its durability.


TECHNICAL SPECIFICATIONS

Displacement: 3,49 cc

Power Output: 2.65 PS/2.61 hp @ 34,000 rpm

Practical Range RPM: 4,000 - 42,000 rpm

Bore x Stroke: 16,40x16,40mm

Sleeve: 3 + 1 ports

Rear Ball Bearing: ceramic

Front Ball Bearing: steel

Crankshaft: 14 mm

Carburetor: 21 J3

Glow plug: P3 Turbo

Exhaust Position: rear

Fuel type: Recommended Nitrolux Energy3 16%-25%.

PIPE AND HEADER

This is the Ultimate Racing Super Strong EFRA 2142 exhaust system. This EFRA 2142 hi-quality aluminum exhaust has been designed to improve the overall performance of your engine. This pipe set provides a precise and linear throttle response in high RPM range with a great top end speed. This pipe set will provide great power and speed at high RPM. This EFRA 2142 exhaust system is a great choice for your 1:8 off road engine, and it’s specially recommended for the M3R, M3X, M4R and M5 Ultimate engines. This exhaust system includes the pipe, the manifold, 3 short springs, 2 medium springs, 1 long spring and 2 manifold gaskets.

Shipping Notes
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Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
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SKU: 50561105411

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marsha
Omaha, US
★★★★★ 5
Great product!
Size: 5 Ounce (Pack of 1), Style: SPF 50+
I took this to Hawaii. It's great sunscreen and good to use in the ocean
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Reviewed in the United States on June 1, 2026
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Amazon Customer
Charlottesville, US
★★★★★ 5
Safe for reefs
Size: 5 Ounce (Pack of 1), Style: SPF 50+
Great product and essential when visiting st John
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Reviewed in the United States on April 28, 2026
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Kelly McGinnis
Cuba, US
★★★★★ 5
For Professional Outdoors Folks, THIS WORKS!
Size: 5 Ounce (Pack of 1), Style: SPF 50+
I am in the sun approximately 300 days a year and I have used everything available. I am on the water daily and there are only 2 products that 1) work and 2) stay on when wet; Blue Lizard and Doo's. Both have nutrients and moisturizers keeping your skin young. This stuff WORKS! Highly recommended.
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Reviewed in the United States on April 23, 2026
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J. M. C.
Lowell, US
★★★★★ 5
Worked well for 4 days spent poolside in 104° temps
Color: White, Size: 0.15 Ounce (Pack of 1)
I purchased this specifically for the Zinc/ mineral based SPF factor. There are not a lot of great options for a sun BLOCK lip balm. This is about the highest SPF I could find, in a tube/stick applicator. We use 70 and 50 alternatively and apply often for our bodies and face, but we needed an extra layer for the lips. (They really are very delicate tissues) We like the texture, I didn't notice a flavor or odor, so I guess that's good right? I did not see any white cast to it and honestly I would not care if it did, I just want a sun block for my lips while we are poolside. It worked well. A slight tingly feeling to my lips for the first 30 seconds when applying it, but it did not sting or irritate my skin/lips. We went 4 days of poolside lounging and swimming with about 5-6 hours a day at the pool. We were in and out of the shade, in and out of the water, at at very dry desert Nevada 104° sunny location. We reapplied about every 1.5 - 2 hours, or if we felt like we needed it after eating or drinking something. We did not burn nor peel, our lips were soft and great. I will keep using it and will likely purchase again, when needed. It's a good brand. Aside from straight up old fashioned white or colored lifeguard zinc sticks, this is a less "clown like makeup" option.
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Reviewed in the United States on July 11, 2025
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Jessica S.
Boise, US
★★★★★ 5
Great Product
Color: White, Size: 0.15 Ounce (Pack of 1)
This lip balm was recommended by my surgeon to protect my lip from uv rays. Surprisingly, it does not have that yucky spf taste other lip balms have. It does create a white cast, but I find if I lightly put it on the cast is not prominent, and I am Caribbean with deep tan skin. Very grateful this lip balm does its job!
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Reviewed in the United States on March 1, 2026

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