Air cooled, four stroke, single cylinder, OHC
Bore x Stroke
56 X 49 mm
1X 26 keihin
12.5 @ 10000 rpm
818 mm / 32.2 in
106.6 kg / 235 lb
Over the past decade Honda has whittled out some amazingly
successful motorcycles. Three have been quite conventional in design—Honda's
350 twin, 90cc horizontal single and the 125cc vertical single. These sales
classics have done nothing very well except sell in phenomenal numbers.
Honda continues to roll ageless four-strokes off the assembly line at the
rate of one every 20 seconds. When combined, Honda's trio of sales leaders
has placed a total of 1.5 million motorcycles in American garages since
1959. Of the trio, the 125cc vertical single is the most recent. As
originally introduced five years ago, the SL125 was an inexpensive street
bike with boring performance and incredible reliability. And these qualities
are strong in the new XL 125.
Understanding what the XL-125 does and doesn't do well will
save interested buyers future disappointments. Honda's XL-series machines
encompass their four-stroke single trail and enduro type bikes. The XL 125
falls short of delivering off-road performance like the Penton, Can Am or
even the Kawasaki KS 125. The 11.14 horsepower engine just can't pull the XL
around with gusto.
On the other hand, the XL 125 offers low operating costs, dependability,
quietness and cleanliness—things that more spirited two-strokes don't have.
And the XL is the only four-stroke in the vast field of 21 different 125cc
trail and enduro bikes.
If you don't like two-strokes, mixing oil and gas, wet
fouling spark plugs, seizing pistons and other smokey side-effects of the
ring-dings, then the Honda XL is your only choice.
By two-stroke standards, the XL 125 engine is a maze of complexity. The
engine assembly, comprised of 232 parts, is still modern in every respect.
All aluminum castings house an overhead camshaft and an all-bearing
supported crankshaft and transmission. Wet sump
lubrication uses the same oil bath to coat both the engine and transmission
parts with 1.6 quarts of 10W 40 weight petroleum.
The trochoid oil pump
drives off the crankshaft pinion gear and pushes lubricant to the
crankshaft, camshaft and transmission. A centrifugal filter is mounted on
the crankshaft end.
The engine remains externally identical to the original SL models.
Internally the entire valve train has been modified for greater power with
the same Honda dependability.
The rest of the engine is substantially unchanged.
Improvements in the breathing system let the XL 125 develop approximately
more power than its predecessor. In order to house larger valves the seats
have been moved further apart.
The exhaust valve diameter has been enlarged
1.5mm and the intake is 2.5mm bigger. Because the same valve angle has been
retained, the distance from the camshaft center has increased and therefore
the rocker arm length is 1.4mm greater than the SL model. Combined with
increased camshaft lift, longer rocker arms push the valves further into the
The exhaust valve lift is up 0.8mm and the intake is
0.3mm more. In order to decrease flow resistance, shorter valve guides have
been pulled up out of the ports.
Finally, cam timing has been changed and
both valves open five degrees sooner and close five degrees later for longer
The major improvements in the internal breathing system are
aided by a larger carburetor and more efficient muffler. The tiny 22mm
Keihinwas replaced with a larger 26mm venturi mixer. The exhaust system is
all new; it includes a built-in spark arrestor.
When Honda re-issued the 125 as a trail bike rather than a street machine,
off road accouterments took the place of road trim. The high plastic front
fender and mud flap come from the MT 125 two-stroke enduro. The rear fender
is also plastic. The seat and Elsinore-style steel gas tank come indirectly
from the two-stroke enduro bikes. Also from the MTs are the handlebars,
levers, controls, instruments and fork assembly. A final trail touch is the
inclusion of the block pattern trials-type tires.
To the inexperienced eye the XL 125's decor says fra/7. In
fact, however, the bike possesses better street than off-road qualities. The
new chassis is more slender than the SL running gear but it's still heavy
and quick-steering. The cumbersome weight, slow acceleration, skittery tires
and terrible rear damper units will keep riders away from any but easy,
hard-packed trails and roads.
For a small bike the XL 125 is comfortable. Location of the hand controls is
proper, the spring-loaded folding foot pegs are correctly placed, and the
long solo saddle remains comfortably firm. Overall comfort for tall and
short riders alike is superbly compromised. The 32 inch saddle height allows
all but sub-5'6" riders to touch the ground easily.
A full complement of street necessities come on the XL 125.
Turn signals are rigidly affixed to the headlamp ears and rear frame member.
The large tail light sits high on the rear fender and places the license
vertical to the ground. Instruments include an 80-mph speedometer with an
enduro tripmeter and a 12,000-rpm tachometer. High beam, turn and neutral
indicator lights are bright and visible. The headlight glows only when the
engine is turning the six-volt AC generator.
The ignition key is located under the left side of the gas
As expected, cranking the engine through requires minimal effort. Cold
starts require closing the choke butterfly fully and three swift kicks. The
XL 125 engine is cold-blooded and the choke must be flipped open in gradual
stages over a five to ten minute warm-up period. The tachometer needle
climbs at an even rate to its 9500 rpm redline. There's almost no engine
noise, and the exhaust rap is nothing more than a rapidly muted
Engine response in all gears is gradual; there's no surge at any point.
First gear is relatively low and permits poking along comfortably on flat or
slightly graded terrain.
A moderate jump to second gear taxes the engine in sand or
on grades. The first-to-second span gives no trouble on street or
hard-packed dirt roads. Equal spacing between second, third and fourth
enables the bike to accelerate smoothly up to 45 or 50 mph. Fifth gear is
set away from fourth and serves as an overdrive on asphalt.
Operation of the throttle, clutch and gear lever is exceptionally smooth and
easy. A soft spring in the Keihin carburetor makes throttle twisting easy
and non-fatiguing. The equally soft clutch lever demands little hand
pressure. The friction point arrives quickly as the lever is released but
the flywheel inertia of the four-stroke single smooths out gear engagement.
The transmission glides from one gear to the next. The rider must use the
clutch to assure full gear engagement.
As with any small displacement bike the clutch is engaged
and disengaged constantly in order to maintain speed. The big oil-bathed
multi-plate unit will take great abuse with little complaint or fading. The
overall gear ratio is too high for the vast majority of off-road needs.
Installation of a countershaft sprocket with one less tooth would improve
off road performance by allowing the engine to spin faster and remain in its
The XL 125 is most responsive when the tachometer needle is bobbing up and
down inside the 9500 to 10,500 redline zone. The engine runs at its
strongest and smoothest around ten-grand. In order to accelerate, climb or
pull through sand, the engine must run past 9000 rpm constantly as the gear
lever is run up and down. Honda has designed the 125cc engine to rev at the
five-digit mark for long periods. Impervious to lengthy jaunts with the
throttle held wide open, the XL 125 buzzes happily at ten-thousand.
Handling of the XL 125 suffers drastically from
non-functioning rear damper units. The stout chassis has decent geometry
with 29.5-degree head angle and over five inches of trail. The MT-type fork,
with the long sliders and offset axle location, works very well in the dirt.
They are as good as any forks we've seen on a small trail bike. The shock
dampers, however, are typical of the Showa units used on Honda's trail
bikes. They offer absolutely no restriction to spring rebound.
The absence of shock damping allows the rear of the bike to
dance up-and-down like a ping-pong ball on rough water. When decelerating,
the back of the bike rises quickly and overloads the front fork, thus
collapsing the springs unnecessarily. In corners this causes the XL 125 to
dive and plow uncomfortably. On choppy or rocky down-grades the lack of
damping prevents the rear tire from getting a good purchase while braking.
As a result the back end has a desire to come around and
catch the front. The sluggish engine doesn't enhance the XL 125's off-road
handling. Any bike that's down on power like the XL 125 will steer poorly in
the rough and out of turns.
To meet both street and dirt needs the XL 125 is fitted with Bridgestone
block-pattern trials-type tires. These compromise tires meet all of the XL's
street demands but give only passable traction in the dirt. The 2.75-inch
wide front and 3.5-inch rear tires don't deliver the grip of bigger trials
rubber or knobbies.
The absence of bead locks means high tire pressure must be
used to prevent the tire and tube from slipping on the rim. Holes are
provided in the rims for bead locks but they are plugged with grommets.
During our final trail outing we punctured the rear inner tube—a thing of
small consequence with most trail or enduro bikes. The flat tire occurred
while riding briskly over a long, smooth trail at approximately 35 to 40
mph. As soon as the tire flattened the XL 125 went into a convulsive
side-to-side full-lock wobble. At this time the rear tire was rolling
uncontrollably over one side of the rim and then the other. An inexperienced
rider almost certainly would have fallen. By the time we rode slowly back to
home the tire slippage had pulled the stem and ruined the inner tube.
The wheel assemblies are derived from the SL model with its small hubs and
steel rims. The brakes work well in the dirt and are adequate for moderate
street speeds. Behind the carburetor is a large, washable foam air cleaner.
The chassis has plenty of ground clearance. A small complement of tools will
perform most minor adjustments.
Two weaknesses of the XL 125 are not acceptable by 1975
standards. Shock dampers that perform decently are certainly within Honda's
reach. Shocks that dampen slightly cost little more than ones which have all
the parts but don't work at all.
The absence of tire bead locks— especially
on a trail bike—is sinful. Locks are cheap at the factory level and provide
a crucial function for bike and rider alike.
Like its predecessors, the Honda XL 125 does nothing exceptionally well.
It's a small displacement, low-powered street-and-trail bike.
The XL 125
does what it does best on suburban streets and smooth, hard-packed dirt
roads. On demanding trails or open highways it can't run fast enough, go
straight enough or stop quick enough. The XL 125 remains inexpensive, clean,
quiet, dependable, boring and slow. ®
Source Cycle 1975