Excess 750: Yamaha XS650 Motocrosser!

Pikes Peak winner builds a 775cc twin motocross machine!

Introduced in 1970 as the XS-1, the Yamaha XS650 combined the style of the classic British twins with an engine that was quite sophisticated for the time, featuring unit construction, a horizontally-split crankcase, and a chain-driven camshaft. None other than “King Kenny” Roberts campaigned an XS650-powered tracker in Grand National dirt track competition, duking it out with Harley’s dominant XR750, and the XS has gone on to prove itself an exceptionally versatile machine. We’ve seen XS650 flat trackers, scramblers, choppers, bobbers, road racers, dual-sport / adventure bikes, and now…a motocrosser!

The man behind this beast is Travis Newbold of Newbold’s Motorbike Shop — a Colorado workshop focused on performance engine building and suspension tuning. Travis grew up racing motocross, attended Motorcycle Mechanics Institute, and raced down in Baja before the legendary 156 turns of the “Race to the Clouds” beckoned him — America’s last true road race, the Pikes Peak International Hill Climb. In 2012, Travis won the 450 class at Pike’s Peak on a “junkyard-poverty-built” CRF450 he pieced together on a shoestring, then used the winnings to open his shop:

“I decided to pack up my tools and my dog and move to the city, where I would use the money to open up my own motorcycle service shop. I might add there was a rather special girl involved. As with all good stories involving dirt bikes, of course there is a girl involved. With just what most business owners consider pocket change, and the moral support of a good lady, Newbold’s Motorbike Shop was born.” –Travis, Meta

Travis still keeps his foot in a number of racing disciplines.  When he built a fresh motor for his XS650 flat tracker not too long ago, the old engine — a heavily-massaged 775cc unit — needed a home. Travis decided to give the veteran race motor quite the retirement — some golden years on a motocross track!

“The engine is pretty heavily breathed upon, as that is what I do for a living. I estimate it a 75HP lump. The rest of the bike is mostly stock parts frankenstiened together.”

Nicknamed the “Excess 750,” this massive XS650 motocrosser has a stock frame with an RM swing arm, YZ front end / rear wheel, DT400 tank, first-gen Öhlins remote reservoir shocks that Travis restored, and a very trick set of stainless straight pipes welded up by his buddy Gary Pasquale of MONA Creations. Travis says the “Excess 750” might be a tank on the track, but he makes it work against the production motocross bikes of the same era:

“It is a bit top heavy and just plain heavy. It reminds me of riding a big wave runner for some reason. It has no problem spinning the rear wheel with a crack of the wrist. I find myself jumping jumps on it that should not see flight from a street bike.”

Below, we get the full story from Travis on the details of the build, and more gorgeous shots from his friend and photographer Jon Wallace.

Yamaha XS650 MX: Builder/Rider Interview

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.

My life has been racing and wrenching on bikes for over 25 years now. I won the 450 class at Pikes Peak in 2012 and used my winnings to open up my own service shop, where I do mostly performance metric work like engine building and suspension tuning.

• What’s the make, model, and year of the donor bike?

It is a 1979 Yamaha XS650.

• Why was this bike built?

After owning, racing, and building many Yamaha XS’s, I have become very fond of them and I enjoy seeing how many different forms they work in: flat tracker, road racer, hard tail, adventure, and now motocrosser.

• What was the design concept and what influenced the build?

I am a scavenger and it tickles me to spend as little money on builds as possible. I always try to use whatever I have available and lying around. This bike came to be after I built a new fresh engine for my flat track racer. The old engine had many years of redlining around ½ mile dirt ovals and rather than tempt its fate with another rebuild, I figured retiring it to a motocross bike would let it live longer.

• What custom work was done to the bike?

The engine is pretty heavily breathed upon, as that is what I do for a living. I estimate it a 75HP lump. The current crank is not rephased but I did balance it. Displacement is actually about 775cc. I have ported the head and radiused the valve seats; it’s running a Web cam with my own custom specs. Total loss points ignition with Accel coil and VM34 round slides.

The rest of the bike is mostly stock parts frankenstiened together. Stock frame with RM swing arm, YZ front end and rear wheel, DT400 tank, and a seat from the junk pile. My favorite bits are some nice and rusty K&N Supercross handlebars I found at the salvage yard and the old first-gen Öhlins remote reservoir shocks I restored. My buddy Gary with MONA Creations made the beautiful works of art that are the exhaust pipes.

• Does the bike have a nickname?

Excess 750.

• Can you tell us what it’s like to ride this bike?

It is a bit top heavy and just plain heavy. It reminds me of riding a big wave runner for some reason. It has no problem spinning the rear wheel with a crack of the wrist. I find myself jumping jumps on it that should not see flight from a street bike. If the landing is not stuck perfect it sure lets you know! The brakes don’t do anything whatsoever but luckily it has strong engine braking.

• Was there anything done during this build that you are particularly proud of?

Oh you know, just the sound of a straight piped twin firing up; it’s hard to beat!

Editor’s Note

We highly recommended Travis’s piece “Motorbikes Saved My Life” over at Meta.

Builder Thanks

@jonwallace_ took the killer photos, and @mona_gary built the exhaust.

Follow the Builder

You can find Travis and his shop @newbolds_motorbike_shop and his personal blog: 747rider.blogspot.com