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O.S. Speed B2102 .21 Low Profile Off-Road Nitro Engine (Turbo Plug)

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This is the O.S. Speed B2102 .21 Off-Road Nitro Engine. The innovative B2102 engine comes equipped with a low profile head which provides great influence to the running performance. The low-profile cooling head (-17mm) makes the vehicles center-of-gravity much lower, which improves car handling drastically without sacrificing cooling performance.

The B2102 also comes equipped with the O.S. 22C (B) carburetor for improved fuel mileage to go the distance; ten-minute runs on a single tank are no longer a privilege of top drivers with magic fingers.


  • Low cylinder head reduces the buggy's center of gravity by 0.67"
  • (17mm) for better stability during aggressive driving
  • Redesigned 22C slide valve carburetor for better fuel economy
  • Tungsten weighted crankshaft with diamond-like coating and silicon potting
  • Bypass of crankcase is modified for better performance

Displacement: 0.211 cu (3.46 cc)
Bore: 0.646 in (16.40 mm)
Stroke: 0.646 in (16.40 mm)
Practical RPM: 4,000-42,000
Power Output: 2.65 PS/2.61 hp @ 34,000 rpm
Crankshaft Size: UNF1/4-28
Distance/Mounting Hole Centers Same Side: 0.83" (21mm)
Distance/Mounting Hole Centers Opposite Side: 1.45" (37mm)
Width of Crankcase below Mounting Tabs: 1.2" (31.6mm)
Width of Mounting Tabs: 1.8" (45mm)
Height/Mounting Tab to top of Cylinder Head: 2.6" (65.9mm)
Height/Mounting Tab to center of Exhaust Outlet: 1.1" (28mm)
Height Crankcase Bottom to top of Cylinder Head: 3.2" (81.5mm)
Length of Crankshaft end to Front Bearing: 1.2" (29.5mm)
Length of Crankshaft end to Backplate: 3.7" (94mm)
Length of Crankshaft end to Center of Crankcase: 2.9" (73.5mm)


  • O.S. Engines Speed B2102 Engine with P3 Turbo Glow Plug
  • 6.5mm Carburetor Reducer in Red
  • Exhaust Seal Ring
  • One each 3mm, 16mm and 18mm Dust Caps
  • Instruction Manual

Carburetor Settings: (Carburetor is preset from factory and should only require very small adjustments)
Needle Valve: 3 turns open from fully closed
Mixture Control Valve: One turn screwed in from flush position with carb body
Metering Needle: 0.3-0.4mm protruding from flush position with carb body
Throttle Stop Screw: Approximately 0.5mm from carb body when viewed from above

This product was added to our catalog on January 13, 2017

Andrew Darby
Average Rating: 5
Verified Owner
Thursday, Aug 30 2018 (6 months ago)
O.S. Speed B2102 .21 Low Profile Off-Road Nitro Engine (Turbo Plug)
I bought a few Sauare Stroke and Long Stroke Engines when I got back into Nitro after a few year break, and have ran them for a handful of races switching after say a gallon then run the same tracks with the other. I had a B2101 and the B2102 use the same P/S/R, I've measured ports, the case, crank timing is the only dimension I can't get exactly which could cause more power. But my B2102 feels identical, and once the metal pinch fades away and the engine is FULLY broken in, my engine felt identical and ran identical to my B2101 with the same 2090 Pipe and fuel. I ended up preferring the Long Stroke XZB II style engines but the Speed is worth the money (mainly or especially when they're on sale or A Main has a good $30-40 coupon code which they always do plus free shipping) because you're guaranteed to get an amazing engine, made with top quality Japanese materials, hand matched P/S, DLC crank etc. What a lot of people forget is that these engines aren't meant to be thrown away after they loose power and are worn out, you can pinch the sleeve maybe replace the rod and keep going. The case, DLC crank, head button, etc can be used with over a handful of Complete rebuilds. Pay $500 once, and after 10 gallons, pinch it if that's you're thing for $30 bam another 6 gallons, then get a complete P/S/R set for $220 and the engine is brand new like day one. Bearings you'll want to watch but can get a full set for $30. There's a reason there are 10 OS Made Engines to 1 of any other brand. Try the VS Racing Engine, less expensive, makes more power, and is designed by World Famous Engine Maker Rody Roem.

Average Rating: 4
Thursday, Aug 23 2018 (6 months ago)
O.S. Speed B2102 .21 Low Profile Off-Road Nitro Engine (Turbo Plug)
The uninformed and cheap among us will never appreciate OS quality. I've run every brand there is, and always come back to OS. That being said, thi sengine is lower on power than the B2101, which is why Tessmann put a B2101 crank into this engine and called it the Ty2 silver head engine that for some reason AMain doesn't carry. The 2102's lower power isn't a good trade off in my opinion because the engine doesn't produce significantly more run time. Still a great engine and I like the lower cooling head height during non summer months.
Mike Bayus
Average Rating: 5
Sunday, May 14 2017 (about a year ago)
O.S. Speed B2102 .21 Low Profile Off-Road Nitro Engine (Turbo Plug)
I don't care how long you've been manufacturing your engines or how great they are... I will never pay 500$+ for a nitro engine period. Time to take your marketing gimmicks back to the drawing board....