Our Pro Caliber Yamaha YFZ450

By Kory Ellis
This year was an inspirational year for ATV racing. Not since the three wheeler days have so many ATV manufactures been represented on the line of a pro ATV national!

I’m here to talk about our parking spot on the line and what we parked there, — the 2004 Yamaha YFZ450.

Below I’ll fill you in on all the changes we made to the ATV Scene.com YFZ test quad that yours truly raced at the final three MX GNCs of the 2003 season.

I’ll reveal each and every detail performed on this quad and what I did to it to win on it. By the end of this article you’ll have all the information on what it takes to modify your YFZ into a pro-caliber-race-winning machine!

Gone are the days of spending a ton of time and money on your motor. You can run this baby stock and win! Note that the GYT-R countershaft guard and shifter can be seen in this photo.Motor
Not much to write about here. Yamaha breathed all over the YFZ powerplant to get every pony out of it possible. Then, unlike typical past OEM quads, they amazed me by releasing all this valuable know-how in the made for public version. This motor is packed with just as much hi-tech modern-day horsepower as the bike guys get with their 2004 machines. In case you didn’t know, it includes five titanium valves, an all aluminum body, ceramic coated cylinder, ratchet type five-speed shifter, direct ignition coil, and magnesium valve cover all shared from Yamaha’s YZ450F dirtbike.

We did make a few minor changes to get a little more oomph out of our YFZ however. Here’s what we did.

Add a pipe or don’t plan on running up front
Yamaha supplied us with their GYT-R Full Titanium pipe. Power gained from this simple ten minute mod is simply incredible! You’ll want to re-jet the carb and toss the airbox lid. After that, be prepared for a whole new quad – one with ample power throughout. I was amazed how the motor responded. The powerband was greatly improved everywhere! Of course the pipe is louder than the stock pipe but no louder than any other aftermarket pipe, and after all this is a full blown race quad, it’s supposed to growl a little.

Piston
The stock forged piston is based on the YZ450F, but not identical. The compression ratio is 11.9:1, not bad but we thought we would try to get more compression out of the motor. I raced the Mt. Morris GNC with the stock piston. The motor performed so well that I almost didn’t want anyone touching a thing. We couldn’t help but tinker though, so we installed a 13:1 GYT-R high compression piston. I noticed a slight improvement but surprisingly it was minimal, especially compared to the gain we saw from the pipe. All in all, in the pro class you need every little bit of power you can get. So far the reliability of the higher compression motor has been great.

Clutch
Yamaha hooked us up with a GTY-R billet clutch basket, GTY-R inner hub, GTY-R pressure plate and capped the clutch package off with a GYT-R clutch cover. These improvements are lighter than stock, aid in heat dissipation and improve the clutch performance. Their pressure plate/inner hub also incorporates a nifty oiling system which help extend clutch life. Long twenty minute pro motos even in Loretta Lynn’s kind of heat showed no problem for our YFZ’s new aftermarket clutch package.

That little black box can pack a mean punch
Eventually we swapped the stock CDI box for a GYT-R Rev Box in order to let our YFZ run to its maximum RPM ability. It definitely did just that. The rev limiter location is increased to 11,200 rpm (stock is 10,750 rpm), which is very similar to the YZF’s.

You’ll want to retard the exhaust cam timing if you want to move your powerband a little more toward the top end. If you elect to switch to a kick starter, this mod is a must do. The cam timing cannot be left stock if you want to kick start it.Retarding the exhaust cam timing
This mod simply moves the power a little more toward the mid-to-top end and away from the bottom-to-mid end. This is basically a personal preference, unless you elect to bolt on a kick start system, then it’s mandatory. If you like your power a little more on top, it’s safe to move the exhaust cam one tooth from top dead center.

To retard the timing on the exhaust cam first find top dead center (refer to shop manual), relieve the pressure from the cam chain tensioner, pick up enough slack in the cam chain in order to move the exhaust cam one tooth on the chain in a clockwise direction. Know that the intake cam will have to be moved in order to create enough slack to move the exhaust cam. In this diagram, at top dead center, you’ll notice that on the left (stock) there are 14 chain link pins from the white dots that we painted on the chain. On the right, after we moved the exhaust cam, at top dead center, there are only 13 cam chain link pins from white dot to dot. As you can see, we’re actually retarding the timing by one tooth. This lets the motor rev a little more on mid-to-top end of the powerband. When adjustment is complete make sure the horizontal timing dot on the intake gear is visible and horizontal with the gasket surface on the cylinder head.

A YZ kill button is converted to an electric start button. Also note the GYT-R hot start assembly on the GYT-R clutch perch.Losing Some Weight
In the past, when OEMs didn’t make ATVs especially for racing, we would spend countless hours trying to get rid of dead weight. The YFZ comes stock at 350 pounds – not too bad, but thanks to Yamaha’s planning ahead, we could easily shed additional weight by scrapping the electric starter, battery and other needed drive gears and clutches. We felt that the weight loss and reduction of rotating mass could enhance performance, so we took up Yamaha’s kick start weight-loss offer and installed their GYT-R kick shaft kit as well as their kick crank kit. Yamaha had enough sense to equip the YFZ with the same exhaust cam shaft found on their WR450F bike, which offers easy starting with its auto decompression cam pin and lever. Yamaha’s hot start button is integrated on the GYT-R clutch perch, but but does not come with their kick start kits. However their hot start cable does – just screw it into place on the carb. For those wanting to remove the starter motor like we did, you’ll need the GYT-R starter plug to cap the spot the motor used to be in.

Yamaha’s kick starter accessory kit even includes a template for cutting the perfect amount of material off the rear fender to allow your foot to pass by the fenders. As you can see, they thought this out pretty carefully at the drawing board. Make sure to unplug the radiator fan if you remove the battery. If you don’t, the fan will rob precious voltage away from the spark plug and the quad will not run properly. You wont need the fan for motocross, but if you plan on racing cross country events or dune riding, you’ll need the fan to properly cool the motor, so don’t remove the battery. Also, in order for the kick start kit to work the camshaft timing must be changed to the YZ timing by retarding the exhaust cam one tooth as described above.

As a motocrosser, I was happy to shed some weight but found one problem along the way. Although the motor starts easy enough with the kick starter, I have to admit, I grew a little attached to starting the quad with my thumb. I’ll even openly admit that I stalled the quad at the YFZ’s debut at Mt. Morris but since it had the electric start at the time, I fired it up instantly and only lost about one second of time. Not to mention, we only saved about seven pounds of weight, so I’m not so sure if this mod is such a hot set up or not.

As far as performance goes, the PEP ZPS shocks and long travel +2″ Lone Star A arms top our list of must haves for pro-level competition. Check out the roost deflecting Quad Tech Stealth SPS (Shaft Protection System) on the PEP shocks.Suspension & Chassis
Priority number one for motocross racing is to widen out the quad. Thanks to Scott Butler at Lone Star this was no problem, even in our hurry up rush. We fitted our quad with a set of chrome Lone Star +2″ A-arms. In the rear, we swapped the YFZ swingarm with a Lone Star unit. We did this mainly so we could easily slip an in-stock LSR Twin Row bearing carrier in, all so we could slide the Lone Star’s Axcalibar variable width axle through. LSR steel-braided brake lines were added at this time as well. We locked down the axle with LSR’s Disc Brake Hub and a LSR sprocket hub with a Honda bolt pattern so I could use all my current gears. LSR’s Micro-lite hubs with Honda lug patterns were used so I could use all my current rims. After that we mounted up Kenda front and rear tires with 1/4 offset Douglas Wheels. These mods widened the quad to 49 1/2″. Next on the improvement agenda were the shocks. Wayne Mooradian at PEP made a set of ZPS (Zero Preload System) long travel with adjustable rebound and compression front shocks for us. Wayne never even saw the quad, yet built us phenomenal shocks based on our specs. They were absolutely perfect. We’ve yet to even adjust them. As for the rear shock, we hurriedly shipped Wayne the stocker. The next day, He re-valved it and replaced the spring, and returned a much improved shock. Since the YFZ starts with a great set of fully adjustable shocks and a well designed rear linkage, the end results were extraordinary! The rebuilt stock rear shock performed as well as any shocks I have ever had! With these mods, and since the YFZ’s center of gravity is positioned perfectly, the end results offer an extremely predicable and well handling race quad! Click the photo for on the left for a handy feature on dialing in your shocks.

The last thing we did at Lone Star was bolt up a +1″ forward 4130 chromoly steel steering stem. It’s a standard height stem with a one inch forward design to give me a little more room.

Here the YZ bike cable is modified to fit the YFZ carb.Finishing Touches
I still wanted a little more room so we lowered the foot-pegs two inches by making the center line of the foot-peg tubes line up with the bottom foot-peg bolt, (AC now offers this style foot-peg mount). We then mounted a set of AC nerf bars to the pegs. At the time AC didn’t make nerf bars for the YFZ, so we used the ones they make for the Suzuki Z400 and modified them to fit. We did the same with the AC front bumper and rear grab bar.

We mounted a set of Tag Metals T2 handlebars. Tag’s T2s are forged from aircraft quality 7049 T-6 aluminum. They’re quality bars to say the least. After we adjusted the bars to where I like them, we mounted a stock YZ bike twist throttle and cable to the bars. Whether you prefer a twist throttle like I do or not, pay attention to the following important information. The YFZ’s stock thumb throttle cable controls the high performance FCR carb,(as opposed to the vacuum type carb that comes stock on the Honda TRX450R, which uses a slower intake vacuum to control the slide position. Comparatively, this gives Yamaha’s FCR carb a much faster throttle response rate).

We looked to Tag Metals for handlebar replacement, added Cycra hand-guards, a GYT-R clutch lever with hot start button, a Pro Design kill switch and a stock YZ bike twist throttle with cable to the controls. The YFZ’s stock thumb throttle assembly is controlled with a single throttle cable that directly controls the up and down movement of the throttle slide.

 

According to Yamaha one of the challenges of utilizing this high performance carb was the safety factor in case of a stuck throttle situation. The YZ twist throttle combats this potential problem by having a separate throttle cable that pulls the slide back down when the twist throttle is turned back to neutral.

 

On the YFZ, which as you know uses a thumb throttle, there is no way to utilize a secondary throttle cable. With that said, the stock YFZ uses an electronic version of Yamaha’s patented T.O.R.S. (Throttle Override System).

This system monitors both the thumb throttle and carb slide positions. As long as they are in sync everything is great. However, if by chance you let off the throttle and the slide stays open, the system shuts down the engine automatically to prevent a stuck throttle situation.

The above explanation is why you don’t want to mess with the stock thumb throttle system unless you prefer to switch to a twist throttle like I do. If so, you will be disabling the TORS system and should run Yamaha’s dual throttle cable system found on the YZ450F. By all means, don’t run a single twist aftermarket throttle cable! Yamaha’s double cable system is added safety insurance that you don’t want to go without anytime you ride. Take advantage of Yamaha’s safety advancements and install the Yamaha stock YZ assembly and cable — if not for your own safety do it for the safety of others on the track with you! To install the YZ cable properly, you’ll need to drill and tap the secondary hole on the YFZ’s throttle body to allow the ability to use the push-pull YZ cable.

Cycra MX style hand shield guards were selected to keep roost from hitting my hands, plus they look great on our YFZ. Tag Metals soft compound grips topped off the bar ends. We went with a Pro Design kill switch. Click on the photo on the right to see how to wire the kill switch. Other valuable additions include a Denton steering stabilizer, a Yamaha YZ chain guide, a lightweight GYT-R billet brake pedal and shifter.

Just before the Mt. Morris GNC practice we trimmed the front plastic with a Drimmel tool. This helps to keep air from gathering under the fenders, which can alter your flight path over big jumps.

I must say Yamaha did a great job in allowing a rider to move around without hitting his knees. The YFZ’s fenders are about the coolest looking OEM plastic ever, so I didn’t dare lose the cool-looking lines they had going so we sculpted sort of a point.

While your carving plastic, you might need to cut out a little bit of the YFZ’s radiator shrouds so they’ll clear the new long travel front end.

We got the quad completely dialed in and had just enough time to put my numbers and place my sponsor decals on it. Then it was off to the line for the YFZ’s debut pro national race, – the Mt. Morris GNC first moto!

Our YFZ is balanced exceptionally. This is especially noticed while airborne.Race Proven
I always take pride in my race quads and make sure they are fitted with the best race components possible. One quad comes to mind as my all time favorite creation. I remember it like yesterday. It was my 1999 Laeger YZ400. I debuted it at the St. Louis Pro Quad stadium race. It was the first of its kind. It featured a mondern-day-high-tech-four-stroke motor professionally mounted in a made for ATV racing Laeger aftermarket frame. Shortly after I debuted this creation, other professional ATV racers built similar machines in an effort to finally better the 250R based pro entries. These machines were completely trick and ultra expensive, but worked on the track like nothing I’ve ever ridden at the time. National champions Doug Gust and Tim Farr would definitely agree with me on this. But that was then, this is now!

Building one of these projects would allow its creator to own the quickest and best handling motocross ATV possible! It also meant devoting about four months of hard labor, scrapping out a YZ dirtbike and squeezing $25,000 out of your wallet to make it all work. Only die hard ATVers would even attempt this kind of thing. Like I said though, it was the best of the best, — until now!

I never thought anyone would come up with anything that would perform better on track than that pro-level ’99 YZ Laeger of mine. I was wrong! It may be hard to believe, but the new YFZ, paired with a few bolt on goodies, like the ones we used above, is indeed actually better!

My first time on the quad was at the Mt. Morris GNC, in the Pro Production class. Thanks to quick acting Lone Star and PEP, we were able to make the quad wider and dial it in for pro-level racing just in time to get it to the track in PA. I didn’t win but they tell me I was boasting the fastest laps of the day on this quad. I came from behind in both motos to put the quad on the podium. I have to say, it was a blast! I was blown away with how well this quad handled and how quick it was, especially in our very first race with it.

The next race was the Loretta Lynn’s GNC. We had a few weeks to dial in the quad a little more and make it even better. It performed flawlessly. I absolutely loved the changes we made and felt confident that I could win that day. I did just that! I went 2-1 to claim Yamaha’s first ever YFZ pro national! With permission from my sponsors, I was allowed to ride this quad again in the pro class instead of the $25,000 Lone Star Honda CRF that I was supposed to race. I bet you never thought you would hear that, right? A pro rider wanting to ride the stocker in the pro class instead of the high-dollar aftermarket racer? Come on! It was true though. I think this is an incredible testament to how well Yamaha made the YFZ! I ended up just missing the podium in the pro class with this machine. I finished a 3-7 fourth place overall.

ATVers get modern day technology straight from an OEM. Check out how clean and new looking our head remained.The last race of the year was the Southwick GNC. In the first moto I finished third. John Natalie went 1-1 to win the overall on his YFZ. I DNFed the second moto. Believe it or not, a pre production test pipe broke at a weld near the front of the motor. Being a guinea pig doesn’t always pay off.

Season Ending Durability Report
After completing the GNC series, ATV Scene’s product support mechanic (and my GNCC mechanic), John Maley, thoroughly inspected the engine’s top end components, including all valve train parts.

His report impressed us. He found no cylinder wear and no valve face or seat wear. In fact, valve clearance didn’t even need to be changed. Valves were cleaned, hand lapped, checked for proper sealing and reinstalled.

The YFZ was raced hard and practiced on even harder. The only sign of wear was found on the frame supports that hold the upper half of the steering stem. As you can see in the photos on the left, both sides are starting to crack near the welds.

We must admit that a hard crash at a local race had a lot to do with these cracks though. Gussets should solve this potential problem in the future. The good news is we couldn’t find any sign of the slightest stress crack anywhere else!

I practiced on the quad about a dozen times as well. All in all, there was plenty of seat time and wear and tear on the machine. As I’ve said before, I’m extremely impressed with this quad! And here’s putting my money where my mouth is! I’m sponsored by Alba Action Sports in Poway, CA, who carries all the major ATV brands, I’ve ridden all the brands and decided to race for a 2004 national championship on a YFZ that we will prepare pretty much identically to this one!

Ellis YFZ450 Specs with prices
Note: items in red were used simply as personal preference and do not aid in the overall race winning ability of the machine.

If you modify your YFZ like ours – be prepared to get a little wet!

Engine Mods	Specs/Manufacturer	Price
Piston	13:1 GYT-R High Compression	179.95
CDI Box	High Rev GYT-R CDI Box	199.95
Clutch	GTY-R billet clutch basket	199.95
	GTY-R inner hub	265.00
	GTY-R pressure plate	149.95
	GTY-R clutch cover	104.95
Exhaust	GYT-R titanium muffler	549.95
	GYT-R titanium header pipe	229.95
Starter	GYT-R Kick Start Shaft and Crank Kit (includes hot start cable)	222.00
	GYT-R Hot Start Lever	49.95
	GYT-R starter block off plug	25.95
Chassis Mods	Specs/Manufacturer	Price
A-arms	LSR +2″ kit (includes ball joints and stainless tie-rods)	760.00
Swingarm	LSR (stock length)	977.00
Steering Stem	LSR chrome (+1″ forward) (incl. bar clamps)	385.00
Axle	LSR Axcalibar (variable adj 1.5″ to 3.5)	410.00
	LSR YFZ Disc Brake Hub	115.00
	LSR Sprocket Hub (with Honda bolt pattern)	135.00
	LSR Antifade Locknut	105.00
Front Shocks	ZPS PEP with adjustable rebound and compression	1650.00
	PEP front shock covers	42.95
	Quad Tech Stealth SPS Shock Guards	125.00
Rear Shock	Stock with PEP mods and a dual rate zero preload spring	700.00
Other	Specs/Manufacturer	Price
Spindles	Stock	—
Hubs	Front: Micro lite LSR with Honda lug pattern	307.00
	Rear: Skat-Trak titanium with Honda lug pattern	345.00
Gearing	Stock	—
Front Bumper	AC Racing	89.95
Rear Grab Bar	AC Racing (number plate included)	46.95
Nerf Bars	AC Racing Pro Pegs	289.95
Fuel	VP C12	—
Oil	Hinson Clutch Oil	—
Chain	Stock 520 O-ring	—
	GYT-R countershaft guard	56.95
Brakes	Stock	—
	LSR steel-braided brake lines	130.00
Controls	Tag Metals T2 Handle Bars	206.95
	Cycra Hand-guards	21.95
	Soft Compound Tag Metals Grips	11.65
	Yamaha YZ450F complete twist throttle assembly with cable	110.95
	GYT-R clutch lever with perch	139.95
	GYT-R billet shifter	93.95
	GYT-R billet brake pedal	116.95
Tether Kill Switch	Pro Design	34.95
Carb	Stock	—
	GYT-R jet kit	49.95
Steering Stabilizer	Denton Racing Steering Damper	159.00
Rear Wheels	Douglas 8×8 beadlock with reinforcing ring	295.90
Front Wheels	Douglass 1/4 offest x10 with rolled beads	134.40
Rear Tires	Kenda Klaw/Gnarly	74.00
Front Tires	Kenda Klaw	84.00
Total Price of mods: $ 10,382.85 . . . . . Total Price of mods, minus products in red: $7,634.15
Note: items in red were used simply as personal preference and do not aid in the overall race winning ability of the machine.

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