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XR650R BASED QUAD

 
(4/17/2013)

As part of the testing duties at Dirt Wheels, we have the opportunity to throw a leg over a variety of machines. From bone-stock new models to full-blown championship-winning racers, no one gets left out. However, from time to time, a machine comes along that stands out. This month, that example is a custom Honda built by Mike Davis out of Eureka, California. Davis is a little different, and he wanted his quad to reflect that as well. He’s not into flash and doesn’t particularly want to draw attention to his machine. His goal was to build a quad that was reliable, handles well and was fast, so he came up with the TRX650R.
PROBLEM-SOLVER
To get his objective, Mike started this project with a 2005 Honda TRX450R. The motor was removed, the frame stripped down and the modifications began. The main reason this build is different is that instead of using the 450 motor that came out of this machine, he sourced a powerplant out of the Honda XR650R dirt bike. This concept is not new, though. Skat Trak’s Greg Stewart and Nic Granlund raced a machine like this in the Best in the Desert series five years ago. However, the way Davis went about building his dune machine was a bit different.
The problem people face when trying to use the XR650R motor in any quad chassis is that it is a kickstart-only powerplant, and the long kickstart lever hits the rear fender when you try to start it. Companies like Baja Designs and Goki have built electric-start conversion kits for the XR in the past, but currently no longer build them. Furthermore, their designs were big, bulky, heavy and, not to mention, ugly.
To get his XR motor started up, Mike sourced a more compact starter kit from a Honda dealership in Switzerland (www.boechat.ch). This unit uses a starter motor of a 400EX quad, a billet-side cover spacer and hardened internal gears. The coolest thing about the unit is that it is compact and looks almost like stock equipment. Mike tells us he purchased the last kit produced, and it was a pain to even get that one. He also tells us he has plans on producing additional kits to sell to XR650R dirt bike owners or perhaps to build more custom quads like this.
 

THE BUILD
Surprisingly enough, the motor-mount modifications to the frame were minor and fairly simple. The XR motor slipped right into the rear frame section that also houses the swingarm. In this case, Davis used a stock swingarm out of a 2006 TRX450R. It’s slightly longer, thus helping to keep the front end on the ground.
The top and front mounts had to be altered slightly to hold the new motor. Plus, the top frame rail (under the gas tank) had to be bent slightly to clear the valve cover. More small modifications were made to install the TRX450R airbox that now sits a little further back in the subframe. For a carburetor, Mike used a 42mm FCR, as this setup was the choice of Team Honda when they used to dominate Baja races using the XR650R. On the exhaust side of this, a custom Looney Tuned system was installed.
Internally things were not left alone either. Mike ported and polished the head, installed stronger Kibble White valves and springs, then capped it off with a Web Cam Stage 2 camshaft. Under the head, a stock bore JE piston with 11:1 compression was attached to a Carrillo rod, and the crank was balanced to perfection by Crank Works. This attention to detail really paid off, as the motor had absolutely no noticeable vibration issues. In fact, it vibrated less than the stock Suzuki 450 we had on hand at the test. Mike did add small plastic damper sheets in each motor mount, which helped as well.
To make sure the engine ran cool in the dunes, an oversized radiator with an integrated oil cooler replaced the stock radiator. This was necessary, as the dirt bike carries its oil in the frame, so it helped add to the amount of oil the quad could carry.
About the only thing left stock in the powertrain were the clutch plates, although they were assisted by stiffer Hinson springs. Tokyo Mods supplied the ignition and the flywheel advance key. To go along with the ignition tuning, a Ricky Stator 200-watt stator unit was used. The extra juice helped provide electricity to a set of Trail Tech lights. An Antigravity-brand battery replaced the bulky stock unit.

CHASSIS
While the chassis was bare, Davis welded in a Lonestar Racing gusset kit. LSR also built the rear hubs, bearing carrier, anti-fade nut, axle, subframe, handlebar clamp and rear hubs. Baldwin hubs replaced the stockers up front. The handlebars used in this project were Fasst Co.’s 15-degree Quad Racer bend. The steering stem was a Laeger’s Racing product  that measured an inch taller than stock. Further down on the front end, a complete Laeger’s Protrax setup was used. This is one of the most complete racing front ends you can buy for any sport quad. It comes with A-arms, spindles and tie-rods. For this project, Fox Float Evol shocks were used up front and a Fox Podium was found in the rear.
Mike tells us Phil Leonard at Alba Action and Paul Seibert of SoCal Powersports were instrumental in the build. Alba supplied the front and rear bumpers, the E-brake block-off plate, and brake-line clamps. Also, in the rear, a custom set of Teixeira Tech rotor and sprocket guards were used. For nerf bars, Mike mounted Houser Pro Bounce products, and the seat was from Quad Tech.
TAKE IT TO THE DUNES
We met up with Mike at the Pismo Dunes to throw a leg over his creation. Before the ride, we inspected the frame, engine mounts and all the accessories. The thing was trick yet not at all flashy. There wasn’t a sign of chrome anywhere. Even the aluminum was unpolished. Don’t get us wrong, the machine was clean and cool. The fabrication on the frame was factory-looking, and even the electric starter was hard to notice as not stock. We do wish Mike had installed all-red full-bore bodywork instead of the mix of black-and-red products he used. It would have been even harder to notice that it wasn’t a stock Honda product.
A small motorcycle kill switch was mounted on the handlebars and employed as a starter button and it worked well. The big thumper started up without struggle. Like we mentioned before, vibration was a nonissue. The big bore idled smoothly and revved up quickly, although you could tell you were operating a much larger mill than a standard 450. All the controls were well placed and worked as well as, if not better than, stock Honda equipment.
When we ventured into the dunes, the Laeger’s, Lonestar and Fox components offered a plush ride. Ripples in the sand virtually disappeared, as did the smaller bumps and whoops. The quad feels light and well balanced. In fact, Davis claims the whole quad with gas only weighs 438 pounds and is almost a 50/50 weight-distribution setup. For example, a stock 450R and Raptor 700 weigh 388 and 422 pounds, respectively. Keep in mind those numbers are with stock (narrow) suspension and no nerf bars.
In the dunes, it was easy to pull the front end up and ride a wheelie for as long as you wanted. In fact, if you were hard on the throttle from a rolling start, you could lift the front end even in third gear. Third gear was about the only gear we rode in. The quad would lug around and never hint at stalling. And if you wanted to take off, all you had to do was stab the throttle and hang on. Speeds in fourth and fifth gear were blindingly fast. The Suzuki 450 we had along for the test was definitely no match for the torque and horsepower Mike’s machine put out. We are positive a stock or even slightly modified Raptor 700 would be left in the dust if put up against this Honda.
Another great thing is that the machine was comfortable enough to cruise around while sitting or standing all day. It wouldn’t wear on you like most modified 450s and all built two-strokes do. Mike’s setup of installing the (right- and left-specific) ITP Sand Stars on the wrong Hiper carbon fiber wheels turned out to work perfectly. They allowed the machine to hold a line well, but if you wanted it to step out, put a little body English into the back end and you could throw a roost to the sun. We couldn’t get enough ride time on this machine. It was that good.
The biggest disappointment in the test was that Mike’s TRX650R is not a production machine. Honda could easily offer a quad similar to this that would run right with Yamaha’s Raptor 700. It is possible that Honda could be working on this project as we speak. If you can’t wait that long, Mike Davis may just build one for you. You can contact him at mechanical concepts@ymail.com.

Topic: Tests

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WARNING: Much of the action de­pict­­ed in this magazine is potentially dan­gerous. Virtually all of the riders seen in our photos are experienced ex­­perts or professionals. Do not at­tempt to duplicate any stunts that are be­­yond your own capabilities. Always wear the appropriate safety gear.
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