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Honda XL 125
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.
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.
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.
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 combustion chamber.
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 duration.
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.
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
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.
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
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.
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.
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