This is part of the name for a type of engine oil, which you have wrongly parsed as meaning something as a group of three words - it doesn't! I suspect that the name of the company might be "X Works" and "Thumper® Racing Full Synthetic Ester 4T Engine Oil" might be the full name of this particular engine oil. In that case, arguably there should be an apostrophe on the end of "X Works", but one would omit it if that were the company's preference.

"Bel-Ray Thumper 4-Stroke Racing Motor Oil is specifically engineered to meet the ... Scott Voltage X Works Film System · Thor Hero Wrapped Motocross Goggle ..."
spy-optic-magneto.purelygreatdeals.info/belray-thumper-racing-oil-liter.htm

"I would be interested in trying this thumper oil to see if it keeps things quiet once its hot. I realise there is going to be some engine ..."
www.dirtbikeworld.net › ... › Manufacturers › Honda Forum

Thumper racing seems to be a type of dirt bike racing, with the "thumper" being a type of dirt bike.

The following mentions thumpers in this context:

"The different sections of 4Strokes.com include: 4-stroke related Articles; books, magazines, manuals, videos, and video games can be purchased through our Buy section; complete Forums for posting and reading about all thumpers; guest image Gallery for posting pictures of your ride; comprehensive Reviews on product and services related to four-stroke dirt bikes; manufacturer Model information on the more popular thumpers; an ever-growing Tech section that includes tips and links to technical information on the Internet; and much, much more!"

http://dirtbike.ws/links/weblink/103

Thumper Racing is also a retailer of motors and accessories for this type of dirt bike.

"We've been around the Big Bore Four Stroke industry for awhile now and have seen them come and go. Our kits and components have all undergone extensive torture test in the real world with real customers, real racing, real endurance riding, and we have fed that back into our kits.

You can experiment yourself on your expensive thumper four stroke, but when you want Big Bore Power that "Just Works" and won't leave you stranded, make your ride impossible to start, or give you power that's unpredictable and "peaky", give us a call."

http://www.thumper-racing.net/

I am not an expert on this type of sport, but I can confidently say that this type of racing is not limited to employees of X works, nor is it run by company X.


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Note added at 6 hrs (2010-05-13 21:39:32 GMT)
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Here's a bit more on motorcycle racing which includes entrants sponsored by Thumper, but the event is not sponsored by Thumper:

http://www.wera.com/
May is packed with WERA Motorcycle Roadracing events. It begins with Pirelli/WERA Sportsman events on the 1st & 2nd at Barber Motorsports Park in Leeds, AL which will host Fast from the Past Vintage Challenge and that same weekend see WERA racers at Nelson Ledges Roadcourse in Warren, OH. Then on May 8th & 9th the Pirelli/WERA West Sportsman Series presented by Lucas Oil moves into Buttonwillow Raceway Park in Buttonwillow, CA. This event has the added attraction of being Round #1 of the CA State Championship (http://www.castatechampionship.com). So the competition at this event should showcase some of California’s best motorcycle roadracers. On the 15th & 16th the Pirelli/WERA Sportsman Series moves to Grattan Raceway in Grattan, MI.
and

http://www.wera.com/legacy/results/1999/summit082999.asp
Vintage 4

1
854
Eric Mercer - Lynchburg, VA - YAM 620 - Sponsors: Millerbuilt Engines, Michelin

2
719
David Temple - W CHESTER, PA - Yamaha 750 - Sponsors: .

3
707
Cliff Murray - CHESTERSPRINGS, PA - YAM - Sponsors: CYCLE MAX

4
359
Ian Cuthbertson - CHARLOTTESVILLE, VA - YAM 600 - Sponsors: SELF

5
253
Mark Mitchell - Richmond, VA - BMW 750 - Sponsors: Moto EuRopa, BALLAS MACHINE

6
138
Craig Charles - Abington, PA - Triumph 750 - Sponsors: Bike Works

7
725
Bucky Sexton - Edgwood, MD - BMW 750 - Sponsors: The Print Doctor, L.C.M. Associates, BS

Racing

8
989
Frank Ty Pecoraro - New Egypt, NJ - Triumph 750 - Sponsors: N/A

98
125
William Alston - LANSDOWNE, PA - YAM 640 - Sponsors: THUMPER RACING

98
777
John V. Stauber - Raleigh, NC - Yamaha 540 - Sponsors: Narrow Focus Prod, Crimson Clock Co.,