Published on April 22nd, 2014 | by Joe0
1985-1986 Honda ATC250R Motocross Project
From Rust to Glory, we turn a stock legend into a modern day vintage motocross dominator!
During the five or six years of mass-produced, high-performance three-wheelers, the 1985-1986 Honda ATC250R set the standard for handling, suspension, and attention to detail. As the only third generation, high-performance two-stoke, the ATC250R had a level of refinement that was unrivaled.Although its out of the box engine performance was a bit lacking in comparison to the 1986 Kawasaki KXT250, or Tecate 3, the detuned red mill offers lots of potential for a skilled engine builder. A little motor tuning and some chassis work resulted in a three-wheeler that was hard to beat on a rough motocross track back in the mid 80s.
Thanks to their robust build quality, there are still quite a few nice, water-cooled ATC250Rs on the used market today. What made them arguably the best machine of the time continues to make the Honda a winning choice in the growing sport of vintage three-wheeler racing.
Inspired by an article in ATV Action magazine from 1985, featuring a National Caliber CT Racing ATC250R, we decided to build our own modern day National Caliber 250R. We wanted our machine to be fully capable of winning races, taking advantage of modern components whenever possible, without wrecking the vintage design and appeal of the machine. We also wanted to provide enthusiasts with a buyer’s guide for companies still supporting the ATC250R with replacement and performance parts.
Our 250R’s rebirth began with a complete tear down. The frame was inspected for cracks, then repainted.We wanted a like-new, wobble-free ride, so a set of All-Balls head tube bearings replaced our worn stock bearings. Eliminating play by replacing worn bearings will improve handling and prevent wear and damage to other components.
With our stock axle carrier failing, we replaced it with a Lone Star Racing Billet Bearing Housing. It features 6061 billet aluminum construction, twin row pre-greased and sealed bearings, and a steel center tube. The housing will work with all stock or aftermarket swingarms and axles.
Simply adding wheel spacers or wider hubs to widen your machine will only put additional stress on an aging axle, making it more likely to bend or break. Lone Star Racing’s Axcaliber Pro Racing Axle is adjustable from between +1 and +4 inches longer than stock. Its extra width improves cornering stability and its wider stance reduces weight transfer in corners, reducing traction for easier, more predictable, sliding. The Axle’s stainless steel construction means no rusting, and its true full lifetime warranty means that it is the last axle you will ever have to buy for your R! The trick billet sprocket hub, all spacers, and new wheel hub nuts are included.
We wanted to significantly improve the 250R’s suspension while keeping it truly vintage, so we turned to vintage dirt bike and ATV suspension experts at Race Tech. They had done kits for the ATC250R in the past and created a custom setup for our Lone Star +1 Swingarm and 205 pound, expert level Motocross Racer, Rob Ray.
Race Tech drilled out the fork’s lower compression holes for unrestricted oil flow and installed their Gold Valve Emulator. The Emulator mimics the function of a cartridge fork, separating out the compression and rebound circuits for individual tunability. The Emulator valve controls compression damping, using various springs and variable spring preload to control how much the valve opens under a given amount of oil pressure.The Emulators are a trick add-on, not enjoyed by racers back in the 80s, so tuning options were more limited back then with the stock forks. Rebound damping is still handled by the original rebound circuit found in the damping rod.Changes in damping are achieved by using different weight fork oil. To finish off the fork, the stock fork springs were switched out for stiffer .47 kg springs. After an initial break-in ride, we switched over to 20-weight fork oil to slow rebound damping a bit.
One other reason we wanted to stick with a vintage fork was because of concerns regarding frame stress, as the old chassis weren’t developed to work with a more rigid upside down fork.
For our rear shock, Race Tech replaced the stock piston with their high-flow Gold Valve. It allows unrestricted oil flow at the piston, preventing mid-stroke harshness, and puts all of the damping work on Race Tech’s custom-built shim stack. Finishing off the rear shock conversion, the under sprung stock spring was replaced with a 5.4 kg spring. Both ends received fresh fluid, and any worn parts were replaced during reassembly.
Between the ATC and TRX250Rs, CT racing has Mickey Thompson stadium and AMA Grand National championships to their motor building credit. Discussing all our options, CT Racing owner, Allen Knowles, felt that a well-built 250 had all the power any three-wheeler racer would ever need for motocross.He felt big bores better suited for the hill shooter and drag race crowd, and since power valves smooth power delivery, they do the opposite of what’s needed to go fast on a trike–– hit hard, break loose, and slide.
Our 250cc class motor received CT Racing’s national porting package. The package includes porting and decking the cylinder, re-chambering the head, and a new LAPC piston with an intake window cut by CT. A top-end gasket kit is included to button it all back up.CT’s National porting package can be set up for pump or race gas. We opted to go with the lower compression pump gas setup, although CT says the high-compression setup makes a big difference in fun to ride low-end power, in addition to increased power across the board. We will try the higher compression setup in the future.
To complement their porting, CT recommends their midrange pipe and silencer, which comes in a beautiful show chrome finish. This exhaust, a rejet, and tossing the air-box lid would also be a great first step in building a competitive race machine.
CT recommends running a Keith 38mm PWK Air Striker carburetor, which we acquired from the carburetor experts at Sudco, who can help you with all your carburetor needs for two and four-stroke models. CT feels this carburetor is the ideal size for their National motor and offers the most jetting options. For the R, CT recommends running the Moto TassinariVForce 3,reed valve assembly.The VForce reeds feature double the edge surface of traditional reeds and travel half the distance to fully open. This is a trick part not available back in the day that CT’s dyno has proven to outperform the competition in horsepower, while providing enhanced throttle response.
CT focuses their power gains in the mid-range for motocross. This increases power across the RPM range pulling well off the bottom, while notably boosting top-end power and over-rev. The CT motor pulls harder than stock from 3500 to 9500 RPMs, producing more than the stock peak horsepower at any point from 5000 to 9500 RPMs. On CT’s dyno, the stock engine puts out 26HP at the rear wheels. Our CT engine is now producing around 42 rear wheel horsepower, nearly 40% more than stock.CT tells us that they can easily build a top-end motor with a higher peak horsepower number, but it wouldn’t be as effective on a motocross track.
To harness all the extra power, we replaced the R’s stock clutch basket, plates, and springs with components from Hinson Racing.Hinson’s Billetproof Basket is used by nearly every top ATV racer in the world. They improve clutch performance, life, and heat dissipation. Machined from billet T-6 aircraft-grade aluminum to aerospace tolerances, and then hard coated, Hinson’s baskets are claimed to last up to five times longer than stock. We can attest from experience that they do, indeed, last far longer and improve clutch feel. Hinson’s clutch plates are machined to work perfectly with their baskets, or your stock basket, inner hubs, and pressure plates. The plates are designed to provide optimum hook up with minimum heat buildup. The fiber plates use organic, non-abrasive materials that won’t damage the rest of your motor as the plate materials break down. Hinson’s Clutch Springs replaced our tired stock springs and are made of quality chrome silicon wire.
With fresh pads recently installed and the rotors in good condition, the only thing holding back our 250R’s braking performance was its stock brake lines. The old stock rubber brake lines were replaced with HEL Performance Brake Lines, which are constructed of stainless steel braided Teflon hoses. The lines feature a non-abrasive PVC outer coating, along with stainless steel fittings, which are permanently swaged together. The front line features a clear plastic guard which runs from the upper part of the number plate, down to the lower fork leg, keeping the line from bending and hitting the front tire. The steel braided lines enhance brake power and feel, while various line and fitment color options let you customize the look of your machine.
Tires and Wheels
Kenda’s Front Max and Scorpion Tires have been around since the three-wheeler days. The 23×8-11 front is an uncommon size due to the 11-inch wheel diameter. The Max features rows of long, perfectly vertical knobs providing good directional control. The knobs are tall for good hookup on soft tracks, while the top of each lug features vertical grooves, providing more biting edges on hard track surfaces.
The 18×9.5-8 rear Scorpion tires lower the machine’s center of gravity compared to stock. Their diamond shaped, dimpled knobs offer a good balance of forward drive with a willingness to slide on loamy or sandy tracks.
OMF’s 8-inch billet center wheels, with super light drain hole beadlocks and reinforcing rings, provide strength, security, and sex appeal. They start life as a strong DWT 190 wheel. They’re then machined to accept OMF’s bolt-on billet centers. Being able to swap out the billet centers allows you to change the wheel’s bolt pattern, offset, style, and color. The beadlocks add strength, and are machined to be light and to allow water to drain from behind them. Most importantly, beadlocks keep your tires from popping off the bead when running lower tire pressure, or in case you get a flat. The reinforcing rings add strength to the inner lip of the wheels and are machined to save weight. Let’s face it–– looks matter, and these wheels scream that this isn’t your average three-wheeler!
Renthal 7/8-inch Vintage Desert handlebars provide the wide clamping area and tall height needed for the old ATC. They are a little wide, though, for riders with a shorter reach. Renthal’s ATV Grips feature a rough, tiny bullet head-like surface that offers great traction, wet or dry, and remains very comfortable no matter how long you ride.
ASV F3, “unbreakable” levers, feature ASV’s double-hinged design, allowing them to bend backwards in the event of a rollover, which is pretty much a given. The F3 levers are constructed of forged 6061 aluminum with stainless steel fasteners. They are completely rebuildable and are covered by a 3-year warranty.
The F3 Pro Model clutch assembly features a trick, CNC, quick-adjust setup, double bearings between the perch and the lever, nylon rotator sleeve, and built-on dust cover. We added the optional ASV dust cover to the front brake lever to dress it up as well.Both levers feature adjustable reach and provide a modern feel. They are available in various anodized colors and add trick finishing touch to your controls.
Complete body Makeover
Maier Manufacturing offers plastic for many vintage applications. Their body parts are thermoformed from TPO polypropylene with a high-gloss cap sheet. We acquired a set of white plastic including front and rear fenders, radiator shrouds, and a front number plate, which we trimmed to fit. Maier’s shine and fitment is on par with their factory plastic. It’s claimed to hold up well to the elements and is proving to be pretty chemical and scratch resistant.
Our stock seat cover was replaced with a custom seat cover from Cosmic Quads. The new seat cover’s construction looked as good as OE and their installation was flawless. All of the logos were properly sized and ideally placed. This is our second cover from them, and so far they are batting a thousand.
The look of our machine’s bodywork was capped off with a set of die cut, Honda ATC250R decals from Motodecals. The kits feature various single color options and replace most of the stock factory stickers, plus a few extras we didn’t recall as OE. They look cool. Just don’t get too nuts with the power washer if you want to keep them that way.
From its appearance in the pits to its performance on the track, our project ATC was like your favorite rock song you’ve heard a thousand times played louder and clearer than ever before. Not quite a show piece, our 250R is undoubtedly a full-on race build where attention to detail like the ASV levers, Renthal grips, and bars enhance ergonomics and give the controls a crisp, better-than-new feel. One kick and a crack of the throttle is all that’s needed to know that our engine has gone through some serious changes, thanks to the deep, throaty sound of the CT Engine.
The motor pulls well off the bottom, despite us foregoing the higher compression race gas setup. This is a help on indoor tracks and when you miss a downshift entering a corner. Big things happen in the midrange. The engine comes on the pipe sooner, hits much harder, then continues building power throughout the midrange and well into the top-end. The power curve works beautifully on the track; CT’s potent midrange punch always seems well within reach with a stab of the gas or a slight slip of the Hinson clutch.This allows you to rocket out of corners and attack big jumps with little runway. At the top-end of the power curve, you have far more leeway to hold it on rather than grab another gear, compared to a piped stocker, or some other motor setups.We have ridden machines that will rev out farther, but don’t work as well on the track.
Throttle response was amazingly improved compared to stock, thanks greatly to the VForce reed valve; in addition to the other motor mods,. This is a big help on the track when you need to quickly lighten your front end or break the back end loose. For beginners, this motor would be a bit much. There’s ample power on tap for experts. Its strong, readily available midrange hit and broad power band give you the power to pull holeshots or run down the competition and capitalize on their mistakes. CT has a fast and effective motor package for the track.
Able to power out of turns faster and hold it on longer in the rough stuff, our machine benefitted greatly from the extra inch of wheelbase we got with our +1 inch Lone Star Racing swingarm. The extra length also shifts the weight bias toward the front of the machine. This helps the front tire bite harder powering out of turns and helps keep the machine flying straight off of jumps with all that extra power.The combination of the longer swingarm and wider axle reduce the amount of weight transferred to the rear wheels and the outside wheel in turns. This makes breaking the rear tires loose easier in turns and improves cornering stability. Along with improving corner exit speeds, the wider, longer setup of the Lone Star products slow the transition a bit before you cross the tipping point.
One racer commented that he had never heard a front tire squeal before, sliding across the ground, late braking into a corner. The extra power and feel provided by the Hel brake lines is very noticeable. A simple brake line upgrade can shave a little time off each lap on an older machine.
Kenda’s front Max provides predictable front-end traction in very different track conditions. The tall vertical rows of knobs provide good penetration and hook up on loamy tracks, and here’s betting they would work well in the mud, too. The rigid knobs’ grooved heads provide additional biting edges providing predictable traction on hard packed tracks. We have tried the rear Scorpions on a variety of tracks and find them most at home on loamy tracks where you want a little more bite than a flat, track tire can provide. They offer a bit more knob than is ideal for tacky hard packed sections of the track; however, when you have to drive off the race line to make a pass, the Scorpions will do a better job of powering out of the corner than a flat, track tire. They work well on many outdoor tracks and are a better option than a modern, sticky compound motocross tire, which offers too much side bite. Our OMF wheels are pretty light considering they are reinforced beadlocks. You can finish a moto even if you get a flat with a beadlock ,and if nothing else, they look incredible.
You have to restore and build a vintage machine to understand how cool it is to complete a project like this. It’s affordable to get into, and you can complete the build up over the course of a couple years. Most replacement and all of the performance parts you’ll need to build a vintage racer are still being manufactured today, and we’ve found that the discontinued parts are out there if you look a little.
As a vintage racer, we think that most would agree that the ATC250R is tough to beat. This project’s handling and suspension would make any racer faster, and its potent midrange motor can easily put some distance between itself and the competition with a good rider on-board.Having beaten every other vintage machine in 11 out of its first 12 motos, our project ATC250R has proven to be more than competitive!It’s also a machine that anyone can easily duplicate.
|Machine||1986 Honda ATC250R||$1,700|
|Porting||CT National Porting Package, Includes Porting, cylinder decking, head re-chambering, modified LAPC Piston and top-end gasket kit||$495|
|Exhaust||CT Racing Midrange Pipe and Silencer, with Show Chrome||$462.95|
|Carburetor||38mm Keihm PWK from Sudco||$265.65|
|Reed Valve||MotoTaassanari V-Force 3||$148|
|Clutch Basket||Hinson Racing, Billetproof||$249.99|
|Clutch Basket Backing Plate||Hinson Racing||$19.99|
|Clutch Plates & Springs||Hinson Racing, FSC Clutch Plate & Spring Kit||$199.99|
|Air Filter||Uni, Foam||$30.95|
|Swingarm||Lone Star Racing, +1in Chromoly||$675|
|Axle Carrier||Lone Star Racing, Billet Bearing Housing||$185|
|Axle||Lone Star Racing, Axcaliber Racing Axle||$449|
|Forks||Stock with Race Tech Emulators, Springs, Oil & Dust seals, inner & Outer Bushings, Oil and Labor||$|
|Shock||Stock with Race Tech Gold Valve, spring, Oil &Dust Seal, Oil & Labor||$|
|Fork Boots||Daystar, 58 Series||$20.00|
|Handlebars||Renthal, 7/8 inch Desert Ventage Bend||$74.95|
|Grips||Renthal ATV Grips||$12.95|
|Front Brake Lever||ASV, F3 Series||$75|
|Front Brake Lever Dust Cover||ASV, F3 Series||$10.00|
|Clutch Lever||ASV, F3 Pro Model Clutch Lever Assembly||$115.00|
|Tires and Wheels|
|Front Tire||Kenda, Front Max 23×8-11||$65 Average|
|Rear Tires||Kenda, Scorpion 18×9.5-8||$46.99 Average|
|Front Wheel||Stock, with gold finish stripped|
|Rear Wheels||OMF, 8 INCH Billet Center Wheels with Superlite Drain Hole Beadlocks and Reinforcing Rings||$219.95 Each|
|Chain||Renthal,R3-2 520 O-Ring Chain||$94.95|
|Front Sprocket||Renchal, Chainwheel 14 Tooth||$25.95|
|Rear Sprocket||Renthal, Ultralight Aluminum Chainwheel 36 Tooth||$69.95|
|Front Brake Line||Hel USA||$49.00|
|Rear Brake Line||Hel USA||$49.00|
|Front Fender||Maier MFG, White||$68.54|
|Rear Fender||Maier MFG, White||$249.34|
|Shrouds||Maier MFG, White||$83.23|
|Front Number Plate||Maier MFG, White 7×10||$8.52|
|Head Tube Bearings||All Balls Racing||$40.69|
|Fork Tubes||New Old Stock from Ebay||$200|