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The 1976 Yamaha YZ125 Monocross

By Matt Cuddy


When I was a teenager, we had a home-made motocross track that was set up at the old Pacific-Electric round house right-of-way on Riverside Drive. The roundhouse was long gone, but the huge empty vacant lot and track right-of-way made for a fantastic long home-made MX track complete with jumps, drop-offs and off-camber turns. “Riverside” as it was known, attracted dirt riders from all over the neighborhood, and since I lived a couple miles away, you could bet where I’d be after school, or on weekends.

There were quite a few “regulars” who frequented the track, we all knew each other, and were friends for the most part. Back then, you could ride your dirt bike to the track, without being hassled by the cops. Since I rode dual-purpose bikes, it didn’t matter.

I was “King” since I had a 360 Yamaha, and could tank-slap my way around the track faster than most people. I don’t know how I survived that bike, it was so out of it performance wise. For instance I took the stock rear shocks off, and replaced them with cast-off units from my Uncle’s ’73 Honda CR250M. They were an inch longer, and put the fork rake on the enduro straight up-and -down, like a trials bike. It made the bike’s head-shake even worse, but those shocks looked trick, so I didn’t care if they were calibrated for a 214 lb. Honda Elsinore, they worked just fine on a 300 lb. 360 Enduro in my beer-soaked cannabis fogged noggin’s thinking.

One afternoon all the regulars were at the track, Karl on his CL100, Marty on his ’74 360 Enduro (green tanker) Dan on his 185 Suzuki, Rick on his CT1 and me on the mighty ’73 360 Yamaha Enduro. We were all goofing around, jumping over people laying down on the doubles, sliding around and making a mess of things generally, when out of nowhere some skinny kid shows up on a new YZ125 Monocroser and proceeded to blaze around our track at light speed.

Of course all eyes went to me, as if asking “OK now crank up your 360 and show that kid the FAST way around” at which point I strapped on my Bell Star 120, stuck my hands in my Webco gloves and started out, after this interloper on his 125 tiddler. Monocross indeed….

Well it didn’t turn out so good. Seems the new Monocross was quite a machine, and on a tight track made mince meat out of my previously unbeatable 360. The final ignominy came when the kid threw up a giant concrete boulder from the roosting Yamaha YZ’s rear knobby, that struck me dead center in the chest, and knocked me right off the 360.

I laid there on my back, stunned, as my friends came rushing to my aide. The 360 had travelled along on its own, and came to rest on a big pile of cast off tin cans of some sort, saving it from any serious damage. I, on the other hand, suffered not physical damage, but the damage of the ego, having been dethroned as the King of Riverside in a scant ten minutes or so. I needed a new motorcycle. Hell, I needed a new identity.

Awe struck our band of Riverside regulars made our way over to where the kid on his Monocross had stopped, to guzzle down some gatoraid, and give us all the steely eye of victory. The bike looked even smaller up close, and the illusion of having no rear shocks made the bike almost other worldly, like some invader from space. The tiny aluminum tank was painted yellow, with the factory race stripes on it, and the one big DeCarbon shock was tucked up under the seat and gas tank, with the mounting point at the steering head. Everything that wasn’t aluminum was magnesium, or some sort of chrome molly. All the bolts had dished in heads, to save weight, and the front forks had big air-tanks on the top, and were already turned down from the factory, aluminum sliders in place of the steel Kayabas we all knew and loved.

In the backs of all our teenage minds we knew things would never be the same, after viewing the latest threat to our dominance of Riverside. This indeed was a portent of things to come, and doomed our so-called dirt bikes to the antiquities department at the local museum.

As quickly as this interloper arrived, he departed in a roost of cement rocks and dirt, wheeled over the far rise of the track, and was gone. My once loyal subjects looked at me with a combination of pity and mirth, the king is dead, long live the kid on the 125 mono…

I was disgusted with myself, and the 360 went up on the auction block as soon as I could get my ad to Cycle News. A few days later some guy came over to look at the bike, but somehow I forgot to put the 360 back in the garage that evening, and it was stolen right out of my backyard. I was now bike less, and dethroned. What a pitiful existence.

But a little history on the motorcycle that dethroned me:


The 1976 YZ 125 Monocross was perhaps the closest thing you could get to a factory racer sold to the general public. It put out around 18 horsepower, and weighed 198 lbs, soaking wet. The motor sported a chrome bore, and a 12 port configuration that maximized scavenging and full combustion of the intake charge. The crankshaft’s balancing holes were closed up with aluminum inserts to maximize crankcase compression, and the six-speed transmission was beefed up with stronger dogs on the gears, undercut for positive engagement.

The only weak link on the bike was the wimpy 428 drive chain that, under the increased load the new motor put out, would snap and wad itself up in the engine cases, and caused the YZ more shares of DNFs than it deserved.

The light weight, long travel suspension and new motor made the bike a real screamer, and also a handler, with the air-assisted forks giving over nine inches of travel, and the rear shock allowing over 10 inches of fade-free long travel rear suspension. The DeCarbon shock was about three feet long, and had a nitrogen gas bladder to compensate for rapid compression and de-compression, along with cooling the unit with inert gas. In 1975 it was state-of-the-art, and would stick around well into the 1990’s over in Europe on small dual sport Yamahas.

The Mono made everything before it an instant antique, and factories scrambled to come up with their own single shock, or dual shock long travel rear suspension. Within five years anything with dual shocks was scoffed at, and soon the dual shock equipped dirt bike was gone, never to return. You can thank Yamaha for this quantum leap in suspension technology.  

Since I used my motorcycle for transportation, I ended up with a 1971 F7 Kawasaki 175 Enduro I bought used from World Cycles over on Sunset for three hundred 1975 dollars. It turned out to be quite a motorcycle, and you can read about it here on the website if you look for the story.

That day long ago, on our home made track off Riverside drive is etched into my memory like a movie. I will never forget getting roosted by a one twenty five cee cee motorcycle, and can still feel, as the Wide World of Sports put it, “the agony of defeat.” No longer could you count on skill and balls to get you around a track fast, you needed technology now too. Something that would take a long time for me to get, being broke most of the time.


The King is dead, long live the Monoshock!