Honda Xr500

HONDA XR500

CYCLE WORLD TEST

At Last. A Big Bore Four-Stroke Dirt Bike That Lives Up To Its Promise

Cleverness tends to tangle, to describe Honda's XR500 as a Great Big Dirt Bike is to play with words and risk some confusion. Big is no problem, as any off-road machine with 498cc. 36 bhp and a readyto-ride weight of 288 lb. is, well, big.

Great? That's gonna take some explaining.

It Iflj\ j1~i require .`~iiie detinulon. \~`~u Lan buy _~ blip within a matIer under. in a bike that's muicli lighter and hiL~h lia~ m~)rc .L1~pCii'.1ofl tra~ ci. For the past c' -eral \CJN the dirt world has bccii mo\ine in the riialI and li~iht direction. So hcrc~ this larce and heav~ machine and h~ kn~t (; reat Ric a contradiction in term.

Because the XR500 is great at doing precisely what some of us want a dirt bike to do.

How Honda has a^gamplished this begins with the original XL250, which returned the four-stroke Single to the dirt, ^he first real progress came with the XL250S, which actually works well in the dirt.

The XR500—also supplied in dual-purpose XL form,—may Seem to be an enlarged 250S. It isn’t. The n^ore one looks at the specifications of *both, the more it appears that the 250 was practice, that all the engineering first seen on the smaller bike was actually intended for the 500.

The XR500 and 250 are masterpieces of integrated engineering, with every component and design based on another part of the bike. Engine height dictated frame design, the front wheel created the exhaust pipes, and so forth.

A^ith the XR500 we can begin with the engine, on grounds that it’s the most obvious difference between the two model lines.

In general, the 500 Single is the 250 Single scaled up. Both use double balancers.rotating in opposition to the crankputting the engine as close to a Single can get. We’re told the smoothness was needed by the stressed-engine frame. Surely if that applied to the 250 it must be even moreso with the 500.

The 500 Single comes in three, well, two and a hall, versions. The street-legal

XL500 is the mildest, because it

federal emissions and noise levels,. The XR has a largejj^rb.jetted for optimum performance, and a lighter (and by a few decibels) louder exhaust. There wîll also be an enduro kit, with higher compression ratiq, a still-larger carb, a Keihin with even a box of jets and a tuning manual, a camshaft with more duration and still another exhaust. Honda really does hope owners get involved with enduros and such. The kit increases rated power to 40.8. Enough, we are told, for anybody. They originally designed a full-race kit with 45 bhp, but not even their team pros could keep the beast on the trail while using full power.

One technut note: The 500 is part of the new Honda family, as in four-valve head and pentroof combustion chamber, like the 2'SO^Smgle, 500 Twin, 750 Four and 104T Sixr But. The other engines use a penthouse (what else would you call it?) piston crown, like a long igloo with a flat roof. The *500 has^âXflat crown. When compression is increased, as with the kit, the piston crown is raised one mm, but it still is flat.

Working on the same puzzle, the CBX Six has a spark advance curve like a set of stairs, and an elaborate electronic control to ensure the sparks are tiifyédjust right.

While most engines*" need added advance all the way to at least 3000 rpm, the 500’s advance curve is all done at 1800 rpm. The 500’s advance control is mechan^cal, good of bob weights and springs.

li8 IS flOt~tM 50Ys~ë~ustion chai~b~ is different. The only clue as to why is that because Honda naturally wanted the 500 to be no taller than it h~d to be, and the engin~e~.~idn't figure the thumper needed a long stroke. the 5~0's bo~ is a whopping *~nni compared th. 62mm for the 750 up to 78mm for the CX500. Valve incl angles are pretty near the same forall tb engines, by the way. while va1vzes~ increase in proportion to the 1*re.

Perha~c-and if Honda R&D wants we'd like to hear from~em-~ t~he bore and thus the chajnbel reaches a certain size the~wir1ing b~fl Flow or flame propagation s~peètor sdt~ thing changes and thus the larger eq~ne needs a different piston crown.

But that's blueprint racing. No~d~ the en~~s wonder at our choice c words on occasiow~

Most useful bit on the 500 is the corn prcssion release, or perhaps .4shoUld be called a compression limiter. As with the 250 and the 185 Singles, the 500 has a linkage attache~ to the kick starter. It opens the exhaust valves just~ the right amount at the right time, so a normal person can kick the engine through and, more important, not worry that the giant is gonna kick back.

The 500 also has the two-pipe exhaust, When commenting on that feature on the 250 engine. we made a comment that only poor Rudge had done this previously. And we got angry letters from Rudge owners.

So. The reason for the comment was simply that umpty-twelve engine builders have used four-valve heads for years. With few exceptions. all these builders have found one exhaust port to work just fine with two exhaust valves. Ergo. Honda does not have the dual exhaust for power. There may be a gain in longevity, as there's a passage for cool air to flow between the pipes and to the exhaust ports. but the real benefit is that the two small pipes can make a tighter curve and clear the semi downtube. which is tucked close to the engine so there's room for the front wheel.

Clever thinking for the driveline and gearbox. As with the 250. the 500 reduces stress fed to the transmission by not multi plying as much torque as is usual. There are some selected additions of material, as in the primary drive gear widened from 12 to 15 mm, and the front balancer going from 19 to 31 mm wide, and the 500 gears are given more extensive heat treatment and are thus stronger for their size.

The major change is due to stress being :aused by impulse rather than pure power. A 500 Four has lighter gears than a 500 Single. for instance, because four cylinders leliver a series of taps while one big cylinder gives big thumps.

Along with larger crank bearings and treated gears. the 500 gets primary drive with coil spring dampers. rather than rub ber cushions, and a coil-sprung hub for the clutch. The larger thumps are cushioned while this solution allows the 500's case to be no wider than the 250's case. Remark able.

Here's some of that Great vs. Big. At 85 lb minus carb. the 500 is awfully heavy for a dirt bike engine. At the same time it's 10 lb lighter than the Yamaha 500 and is smaller. even with the counter-balancers. And the Honda 500 is only 10 lb heavier than the Honda 250 four-stroke. The 500 engine is big. But it isn't fat.

Frame design is like the 250. with stressed engine serving as its own cradle. The frame has a short over-and-under backbone, with head steady at thejunction of backbone and duplex Y cage for the seat. upper shock mounts and swing arm pivot. The latter attaches quite close to the rear engine mounts. The two pairs of mounts share a lug. which should feed swing arm loads into the engine, where they are damped out.

Some of the limits to the four-stroke Srngle turn here into mutual benefits. The 500 engine is by its own nature tall, having the monkey-motion stuff atop the barrel. With no engine cradle, the engine sump can be the lowest part. And because the 23in. front wheel and 8.8 in. front wheel travel dictate a high steering head, the backbone can be relatively straight. which makes it strong. while slanting down to the rear section of the frame and providing a relatively low seat. (We all liked the tank shape. by the way, which may mean we're getting used to the Honda Hump that looked so odd when it appeared on the Hawk 400s.)

Frame tube diameter is the same for the XR and XL 500s and 250s, while the wall thickness is increased for the 500 models and wheelbase is lengthened by 0.4 in. at the backbone for the XL models, the bet ter to provide stability with equal steeringi head rake. Bare frame weights range from 20 lb. on the XR250 to 23 ± for the XL5O(J1

XR500 suspension has some unusual thinking in some different directions.

The forks have only springs and oil. No air pressure supplement. There are hefty triple clamps, with double pinch bolts top~ and bottom. The leading axle is firmly fixed within the lower sliders. The axle wedges directly in the casting of the left leg and is held by a four-bolt cap. just like Honda's motocrossers, in the right Ieg.Re search shows that a rigid axle is vital for good handling. Honda's research has con-., vinced their engineers that an immovable axle is more useful than beefy stanchion tubes, as well as lighter. The XR's sliders are tapered: widest at the top, to allow room for generous bushings and reduced stiction. then thinner, for lightness. The forks use conventional damping rods. The package lacks novelty, compared with what the motocrossers have been doing recently, but getting out of context, there was no sign of front-end flex. For this application Honda has chosen well.

The swing arm, again compared with motocross and enduro models from other makes. looks too small. Flimsy, even. And the shocks are mounted directly atop the axle, while everybody else, along with

Honda on their racing two-strokes, puts the shocks forward on the arm, so as to get more wheel travel from equal shock travel.

The gas/oil shocks are exceptionally long, a full 16.75 in. They tilt forward. This means the leverage changes and the effective spring rate decreases with travel. When the other factories do this, they provide progressive-rate springs or two or three springs of increasing rate, because obviously you need a soft spring for little bumps and a stiff spring for big jumps.

Honda designers had their reasons. A forward-mount shock needs a massive swing arm, because when you have rear forces being fed into the pivot from 18 inches away, and resisted by the shocks maybe 12 inches from the pivot, you got leverage that only a braced and beefed arm can resist. When banging and twisting go directly to the shocks, you don’t have leverage and the arm can be lighter.

This is full circle engineering. Chances are the engineers began with the unavoidable engine height and the seat height they knew rfiost playriders would accept. Ground clearance must be greater than wheel travel or you do a classic bellywhoomper on the far side of a jump. With those limits set, wheel travel came naturally. With limited wheel travel, the XR could afford the light swing arm and backmount shocks. By making shock/wheel travel ratios as close as practical the engineers also gave the shocks more time and travel to do their damping magic, which they do quite well.

Brakes are housed in conical hubs. The spokes are tapered, larger at the hub end, then thinner. This may be more weight reduction, and it’s also true that in some applications a tapered spoke (or any tube) is stronger than a thick one. Because we have only ridden the XR500 for a few weeks and several hundred miles at this writing, we can say the spokes are all intact

and have not loosened more than is normal for a new rim. We can’t say how they'll hold up in the long run.

Tires are Honda’s own Claw-Action pattern, in this case the 6-ply enduro style with an extra row of lugs on the sidewall, vs the motocross pattern with smoother shoulders. The front is a 3.00 x 23. Honda believes in this size, saying that the longer footprint gives more grip and the larger diameter has a better angle of attack, that is, it makes each hole or rut a bit less deep than it would be for a 21-in. wheel.

The XR500 has a series of pleasant touches. The fuel cap is large and can be gripped with gloved hands. The tool bag, furnished standard, has a plastic tray bottom that conforms to the fender, and then is covered with some sort of vinyl top closed by zipper and snaps. The tool kit is held in place with one of those nylon strap and O-ring things. The strap cannot be worked by gloved hands. Or by chilled bare fingers. Perhaps it will stretch with use.

The fenders are generous and have molded stiffness as well as a relief for the hands at the back, for w hen you must haul the bike out of whatever you rode into. The pushpull throttle has the cables routed from the top of the housing, where they are less likely to be fouled or ripped by whatever the rider falls into. There are covers for the lever swivels and the stanchion tubes. The levers aren't dog-legged but they are long enough for good leverage. The mandatory (if you're offering an enduro bike, that is) headlight has a square lens and rides inside a number plate. There's also a tiny taillight.

The XR has a full-length skidplate nicely snugged against the front of the case. Both shift and brake levers are springloaded. which is good because both extend beyond the skidplate.

The lone instrument is the odo-speedometer. The former has a big re-set knob, again suitable for gloved hands. What it doesn't have is an instant re-set. You must wind the dial back to zero, an act that takes forever or seems to if you're right on the minute and due back on the trail. Strange feature not to include.

The dual exhaust pipes curve back into an over-under arrangement behind a heat shield, then join and run in a pipe that looks like a flattened tomato juice can. What it actually does is let the exhaust system tuck inside the frame and righthand shock without blocking the exhaust gas flow. The muffler proper also clears the rider easily. There are no passenger pegs and the warning decal clearly states operator only. No big thing, as the XL series comes with passenger pegs and grab straps so an occasional hanger-on can be accommodated.

So much for the design and specifications. What they add up to first, is a lot of weight. W ith half a tank, our normal standard. the XR500 tipped the scales at 288 lb. That’s a helluva big dirt bike. The open class motocrossers and enduro mounts are mostly 30 to 50 pounds lighter. The old XL. Hondas weighed that much and allowing for model changes since its introduction, the Yamaha TT500, natural rival to the XR500. weighed 282 lb. last time we had one in the shop.

Disappointing. W'e weighed the XR after researching all the features and marvelling at all the effort made to reduce weight, and we were surprised. Let down, even.

But not for long. W'hat all the full circle engineering did was pack more motorcycle into this large package. Every pound is there for a reason and every pound has been put in the right place.

The 500 engine is just about impossible to criticize. The choke knob is on the bars. You needn't fiddle with getting the piston in the right place because the compression limiter is part of the starting system. Choke and no throttle w hen cold, no choke and a crack of throttle when hot. L.eap on the lever and the engine is running. Unless you know, vou’d never guess it's a 500. Nor do vou need to worrv. If it doesn't light early on. keep pushing and it w ill. L here's no chance the lexer will bite back, unlike some other four-strokes and more than a few txvo-strokes we could name.

Uh. wait. There is one way you can tell it's a 500. and that's if you're trained in the old school and ease the engine over onto full compression. That gives a running start on the valx e-lifter. so to speak, and the engine pushes down mighty hard. Best way is not to prepare. Leave the piston xx here it stopped which won't be on compression and kick down.

The 500's good breathing means the power is there without the rest of the engine breathing hard. The compression ratio is relatively low. the cam timing is mild and the result is a soft motor. Plenty of torque and the XR500 gets away w ith a 5-lb. flvwheel. just like the one on the 250 engine. (The XL500 has taller gearing and a 6-lb. flywheel.)

If anybody wants to build a 500 trials engine, here one is. Right off idle, the 500 can't be stopped. You can ride in tight circles at idle, sitting down. tunk. tunk, tunk.

There is no power band, partially because the torque curve is so flat and partialis because the power peak is low. 6500 rpm. Huh. Max be this is why the odd piston crown and the limited spark advance. They don't want you to wind the engine tighter than it needs to go. The 500 signs off relatively early.

Because we xxere also testing the Maico 250 at the time, we ran them together, in drag races. The Honda xxon.

But it took practice, first, the Honda^ rider couldn't hear his engine, not next to the Maico. He was revving too high and he lost.

The w inning secret was to pop the 500's clutch and jump into the lead. Soon as the front wheel came dow n, shift again and it's first to the flag, no matter wTether the 145lb. man or the 185-lb. man was on either bike.

Useful power. Throttle response is immediate. And the response is controllable. The fast guys can get the front wheel up w henever they wish. The slow guys can loft the front when they must. Nice distinction here. Because we like to pretend we are all fast, we sometimes forget to say that for some of us, to lift the front w heel is to risk a loop. Too much power too quickly and over she comes.

With the XR500, though, even the cowtrailers could use the power. What this is, is what we call an “Oh. S***!”, when you crest the hill and find a rut or round the turn and confront a log and it’s too late to stop. Even the pokers could get the XR’s wheel into the air and save the day.

The bike’s limits are set by the gearing. The XR500 is designed to work within a speed range. 0 to 75 mph. The XR has more power than the Yamaha 500 but the Yamaha has at least 10 mph top end on the Honda. At an indicated 75, the XR500 is wound to the max.

Kind of a surprise. Gearbox ratios are normal, w ithin fractions of the TT500 and the Husqvarna OR390. Doesn't feel like it. though, because the XR is so tractable at low speeds and has such a low top speed and while on the way from one to the other, you’re always shifting up.

What it is. though, is that the balancers and the beautiful throttle control of the 500 let the engine work well at lowest possible revs. When the Yamaha leaps forward three feet w ith each great Whump of its piston, the Honda just growls along. And when the Yamaha winds 'way past its peak, the Honda signs off.

This may be on purpose, the top speed being not especially tops. The XR felt fine at 75. on rough or smooth. Obviously we don't know how it handles faster than it w ill go. but bv the geometry notebook, we wouldn’t expect a problem.

Thing we'd try would be a simple gearing swap. Go up one tooth on the countershaft sprocket. The engine, smooth as a 500 Twin, should still pull well. The internal ratios would be widened, in effect, so you could stay longer in each gear, and there'd be more top end, or less engine speed at whatever cruising speed the trail allows. Open class motocrossers usually work better w ith this change and we see no reason why it shouldn’t be as effective here.

With the engine kit. i.e. racing, taller gears would be even better.

Honda’s wizards also appear to have built something of a speed control into the handling. First, the XR500 tracks so well the racers here say it may track too well. The 23-in. tire grips all the time and at speed it can be difficult to wrench the bars off the straight. Then, because the front wheel is grooved to the surface, the XR doesn’t like to slide. This is accentuated by the soft suspension and grippy rear tire. The tire will bite and load the suspension and when it’s loaded, the rear will drift out and the suspension unloads and the tire bites again, all in a cycle quicker than it can be described. On a fire break or powerline road the only workable technique is to pitch the bike in. pivot on the front wheel, throw the back out with full power and correct as the tire bites. Our racers say they don’t really like being told what to do by the bike.

For the rest of us, the slowpokes, this sounds elitist. The XR goes w here pointed. You needn’t be out of control to be in control, and for those of us w ho relv on the machine to save our silly necks a dozen times a day. this stability is a virtue beyond price.

The suspension is astonishingly good. The figures, that is, 8.8 in. travel in front. 7.8 in. in the back, sound average for a playbike. They aren't, because of the weight. Funding a 450-lb. package from a two-foot jump naturally uses up more travel than will a 375-lb. package, so 8.8 and 7.8 inches on a 288-lb. bike isn’t like the same wheel travel on a 210-lb. bike. Especially when the books say the heavy bike’s springs are getting softer as they get closer to their stops.

Doesn’t work out that way. Okay, you can bottom the XR500. You can bang both ends into their stops off jumps or over severe cross grain, and you can bottom the rear shocks on w hoops or w hen you charge full boogie into a bermed corner.

But it doesn’t happen often. At the end of the first day. the heaviest rider was talking new springs and both he and the lightweight w'ere thinking air caps.

T he XR500 suspension works. Only real flaw is that on a rocky uphill the soft front sometimes w ill bounce out of the line. The rest of the time, once we’d figured out that just as a heavy bike lands hard, so is it less likely to jump as high, the supple ride came into its own.

The back wheel doesn’t chatter, even without a full floating brake. The XR will run across deep whoops at rapid speeds with no sign of the back kicking sideways. The soft springs soak up the bad parts and the damping is just right, lets the easy ride keep the back wheel on the ground. There is a provision for pre-load, with a ring you can set in one of three grooves in the shock body. By the end of the second day. the light man figured he’d leave both ends alone and the heavy one thought full preload would take care of him.

The XR’s rear shocks are the best we’ve> ever tried on a stock four-stroke enduro bike. Further, we couldn't think of any aftermarket shocks we’d tried, and during tests in 1977 we tried every one we could find, that worked any better than these. Remarkable. How far we’ve come since when you automatically threw the factory stuff' away.

HONDA

XR500

$0000

The Claw Action tires deserve some separate mention, but they won't get it here. The XR worked beautifully in sand, mud. rocks, snow and even glare ice. Some of this must be due to tire. We considered trading tires, just to see which was doing what. On second thought, no. The XR500 comes with the Claw tires, so it wouldn’t be fair to try one without the other.

The actual tread design, we’ll test against other tires in a knobby group comparison now in the works.

The 23-in. wheel? We’re of two minds about that. Honda obviously believes in the theory, and one doesn't like to bet against Honda. They’ve got the big wheels on the CR125 this year and their thinkers have obviously calculated that the 23 is better. Hard to argue against the longer footprint, the increased stability and the reduced angle of attack.

Against that, the 23 is harder to steer at speed. And the user is limited in his choice of sizes and treads; you can get two brands, in two models, and that's that. No more swapping Metzelers on adobe for Dunlops in the mud or Goodyears in the rocks.

The 23-in. tire may be another fad. And it may do to the 2 l - i n. wheel what that wheel did to the 19. that is. make it obsolete. We'll have to see.

All controls and fittings and such worked just fine on the XR. except for the seat. Padding good, comfort good, but when you slide forward on the seat, the better to keep the front wheel working on the turns, the flat end of the tank and the fiat end of the seat let the seat collapse and you get your legs caught in the erevass. Also anything else that’s uh. in the way. Ouch. Perhaps firmer padding?

Well. What we have here is a Great Big Dirt Bike. What it does is go quickly, in control, with ease. Got to be the best playbike for the relaxed rider we've ever ridden.

As a contrast, and not a comparison, consider the XR500 and the Maico 250. They are not being compared here. They are not the same type motorcycle.

They are a contrast: tuned 250 and mild 500. The Maico is purebred and high strung. It’s a racer; demanding, quirky, peaky, with great speed for the man who's willing to make the effort.

A fast rider will go faster on the Maico. It's just as quick, just as fast, lighter and with more wheel travel and more precise steering. You can make it do anything you want.

But you gotta work at it. For the man who rides for fun. rather than speed, the Maico is too much of a good thing.

Our slow guys went faster on the XR. The Honda is amiable. There’s power all the time and no excess power any time. Accept the XR as not a motocrosser and it will never bite you. not in 100 years.

Our man who lives in the past thought he'd gone to heaven.

The XR500 “is just like my XL.” he gloated, “except of course that it's got tw ice the power and tw ice the suspension.”

And that’s what we’d call a Great Big Dirt Bike.