O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine

[OSM12180]
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This is the O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine. The 21XZ-B delivers top-of-the-line, affordable, competition-caliber performance and is much more affordable than you might expect. If you like the power of the 21VZ-B V-Spec, the 21XZ-B provides users with improved torque and acceleration. The 21XZ-B features an improved 21J2 three needle carburetor with a 7mm venturi for fine tuned control, while retaining the easy to tune characteristics that OS engines are known for. The 21XZ-B also features a stronger crankcase and weighs less than the previous VZ-B, for improved durability and a lower center of gravity.

Features:

  • Re-designed 21J2 three-needle carburetor
  • 7mm venturi for fine-tuned control
  • Improved fuel mileage
  • Stronger crankcase
  • ABC piston and liner construction

Specifications:
Displacement: 3.5cc (0.21 cu in)
Bore: 16.3mm (0.6 in)
Stroke: 16.8mm  (0.7 in)
Output: 2.5hp @ 33,000 rpm
Practical RPM: 4,000-40,000
Weight: 12.52 oz (362g)

Includes:

  • 21J2 carburetor
  • P3 glow plug
  • 7mm carb restrictor
  • Exhaust seal and dust cap set

Recommended Mufflers and Accessories:


This product was added to our catalog on November 5, 2010.

Wilson George
Verified Owner
Sunday, Jun 10 2012 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
For the price you can't go wrong with an OS engine. Once I figure out the adjustment screw high side low on the carb (which is a mid speed adjustment) this engine screams. Paired up with a JP3 pipe and it keeps up with and out preforms some of the higher end engines out there. You have to take your time and break it in right once it is done, set up and maintaining a tune are a breeze. very consistent engine.
Charles Mims
Verified Owner
Sunday, Sep 25 2011 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
I have 2.5 gallons through this mill and I am very pleased with the performance.great idle with no flame outs. good smoth powerband.I have owned alot of mills but os is the real deal.Its a great feeling to know that this engine is very reliable. THANK YOU OS!!!!!!!!
John Taylor
Verified Owner
Thursday, Aug 30 2012 (about 2 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
I like this motor better then the speed version, seriously. I ahve tried many motors and seem to always go back to O.S. for power, easy tune and reliability. I had the spee version earlier this year and it ran good but I wanted more low end power and this did it. Thanks and under $290 too!!
Sean Dickinson
Verified Owner
Thursday, Jun 21 2012 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
This is a great engine. Not the easiest to break in, but after break-in, it is easy to tune and very reliable. I use P4 plugs in Phoenix, AZ and as long as I have a smooth throttle, I easily get over 10 minutes run time in a buggy. Power is smooth and very predictable, not hard at all to control and definitely worth the less than 300 price tag. Overall pleased with my purchase.
Edward Yishar Quiroz
Verified Owner
Thursday, Feb 20 2014 (about a year ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
Amazing motor lo uso en 2700m sobre el nivel del mar, solo tuve que retirar el restrictor y su rendimiento es increible.
Themistoklis Kardamis
Monday, Jan 6 2014 (about a year ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
AMAZING engine !!! OS will never let you down ! Very easy break in (you MUST warm up the engine first) and is very fast ! I run with some lefrover 20% nitro fuel and i can say both acceleration and top speed are great in my Xray XB9 ! The engine was running at 80C-90C for about 20 minutes (2 tanks 127cc each) with the OS P3 glow plug ! (Ultra Hot) From now on i will run with 25% nitro fuel and OS P4 Glow Plug (Super Hot) i can't believe how fast this amazing engine will be !
Mike Johnston
Sunday, Jul 28 2013 (about 2 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
This is such a great engine! I have mine in a Jammin X1 CR and man does this engine run!! Awesome engine I would recommend this engine to any one just want a decent racing engine. I have a Jammin Jp 4 pipe hooked up too it. It just has so much power!
ALEJANDRO RIBERO RUEDA
Sunday, Jun 16 2013 (about 2 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
Solo puedo decir.... que motor.... Después de despegarlo con toda calma, 5 tanques quieto, y como ocho luego cerrando la aguja de altas de a una hora por cada tanque, empezó a despertar..... tiene todo, pique, fondo y sobre todo, cuando queda en mínimas se siente mejor que todos los motores que he tenido. Lo tengo con la pipa 2060 y de verdad que valió la pena la inversión. Después de varios años de competencias le había perdido el gusto a usar mi buggy por diversión en otro lugar que no fuera la pista, pero con este combo de verdad que dan ganas de salir a correrlo por ahí y gozarse toda esa potencia
Scott Hawkersmith
Verified Owner
Wednesday, Mar 6 2013 (about 2 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
I have raced and run numerous engines...this by far is the best engine for the money,,,I have run the OS speed for years and have found this engine performs just as well without the extra cost....Just be aware this is a racing engine so keep a good p3 plug in it and you will have no problems.....
Sergey Slavin
Monday, Jun 4 2012 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
Very high-priced hobby engine. Not more than hobby. May be I was not lucky with it, but RTR HPI .21 engine was better than this one. Although it didn't crash it's connecting's rod ring on 2nd gallon of fuel! Also 2 cents about it's performance: It's good enougth with right exhaust. 7-8 minutes on tank of fuel in my buggy or it screams and starts overheating. No more O.S. for me.
Marian Miller
Sunday, Sep 18 2011 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
This is a great engine with excellent run time my racing buddy has 2 one for each buggy and truggy & I've never saw him flame out . It actually makes me want to buy the speed version & go that extra mile just to make him jealous .
Alain Lizotte
Saturday, Sep 10 2011 (about 3 years ago)
O.S. 21XZ-B V-Spec Off-Road Competition Buggy Engine
Did't get lucky with this engine. Paid attention to do a very good brak in, but this engine is all but reliable. But the power and speed are very good. I just couldn't get the idle to be correct. It goes slower and slower as the engine is warming. After 5min, the engine want to stall. I replaced the front bearing but it didn't last 1 race day... My friend has the exact same engine and had no problem with it. I guess mine way made on a friday...

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