1971-1973 ATC 90


If you have a question, you MUST read this disclaimer first:

Questions Disclaimer

If you ask me a question without first reading the Questions Disclaimer, I WILL NOT answer you!


Answer to the most-asked ATC90 question: Where to find balloon tires:

They don't exist.

There used to be a few on eBay, and the last set I sold went for nearly $1000.  Keep your eyes on eBay, but be prepared to empty your wallet.



This is the machine that started the whole ATV revolution. It was the first mass-produced all-terrain vehicle priced under $1000. We bought our first ATC, a 1973 model, in November of 1972. I was 11 years old! See Gerard's ATC Page for more early pictures, including one from 1972, and a corresponding photo from 1997.
 

I'm on the right, age 16, in the front yard of my father's house in Salinas, just prior to loading up for a day of riding at Marina Beach in Monterey Bay.  It's 1977 in this photo! The ATC on the left is a 72 model, on the right is a 73 model.  The man on the left is Bruno, the tour guide who took my father and sisters all around Italy in the mid 70's.  Notice that the gas tank of the ATC I'm sitting on is the same as the one used on my ATC shown above.



Here are some mods I've made over the years:

MODIFICATIONS
40 tooth rear sprocket
VW muffler tip
UNI air filter
External fuel filters
Synthetic oil
Removed chain cover
Removed brake drum cover
Removed handlebar brake lever
Case saver chain protector

ATC 90 Wheelie

As a first design, Honda did pretty well. There were some serious shortcomings, though, especially with the rear axle. On the very earliest ATC 90's, the design would allow you to break it apart and store it in the trunk of a mid-sized car. The rear wheels come off, the axle slides out, the footpegs fold up, and the handlebars unclamp and swivel. The whole thing becomes just as wide as the front tire, about 18-24 inches. I don't know why Honda did this. Maybe for markets other than North America, since big pickups are rare outside North America.
 

The problem with this design is that the axle splines get corroded and won't come apart. Since we don't regularly dissasemble these components, we don't know they are frozen until disaster strikes. The drive chain is enclosed in a cover, and it can get loose without your knowledge. A loose chain comes off pretty easy, and trust me, they DO come off. On these engines, the chain comes very close to the engine case, and when it comes off, it bunches up inside the engine case and punches big holes in the case. I think every one of our ATC 90's has a repaired case. We found that welding is best, but J-B Weld two-part epoxy works well too. The big problem occurs when you're out riding and the chain comes off inside the cover. If all the axle splines are frozen, you can't get the axle apart to remove the cover. Some of our friends had to use cutting torches to remove their axles, the corrosion was so bad.

Whoopie!

So, the best advice I can give anyone with an enclosed chain ATV is to ditch the cover, and deal with the dirt. It's worth the extra maintenance you encounter to be able to keep a closer eye on the chain. We also found that the brakes worked better with the cover removed. This is because moisture will get inside a cover, no matter what you do to prevent it. If you don't get the moisture out, the mechanisms will corrode, causing sticky brakes. If left out in the open, the brakes will air dry after they get wet.
 

The original rear sprocket size on the ATC 90-110-125 is 49 teeth. Low range on the two-speed case is too low, and high range is too high. So, to solve the gearing problem, I put 40-tooth sprockets on the back of my ATC's. This also keeps the chain out of the dirt, and makes the tensioner work better, since there is not so much of an angle going back to the engine. This also makes for shorter chains, which as they stretch, don't need as much adjustment.
Another problem with the ATC 90 is the multi-piece cushioned rear sprocket. It consists of a sprocket ring, 4 rubber cushions, and sheet metal retainers to hold the cushions. After years of abuse, the sheet metal retainers get bent, and the cushions fall out. Solid sprockets are much more reliable, and I've not noticed any detriment to the engine's transmission from excess shock loads.

If you are wondering why I removed the brake handle from the handlebars, this is the reason: It confused people into thinking the ATC has front brakes or a clutch. These little machines have rear brakes only, and anytime I would let someone ride our ATC's, they would think the brake on the handlebar was for the front brakes or the clutch, and they'd grab it at inopportune times, such as going up a hill.


ATC 90 Paraphernalia

Jigsaw Puzzle

Woohooo!  Check the parking brake...it's on, and her thumb isn't even on the throttle!  I still own this...note the $1.29 price tag!

Plastic Model

I have one of these from the mid-70's.  It's assembled, and sitting on the shelf behind my computer.  This is a photo of the box the model came in.  There was an unbuilt one on ebay a while ago that sold for over $50!



Links!

www.atc90.com

A great site for ATC 90 fans


NEWS!
Well, ATC 90 fans, it's great news! It appears that IMS is making a plastic gas tank for the 69-82 ATC 90 and the 83-up ATC 110 and 125! YIPPEE! You can order one from Chaparral Motorsports at 1-800-841-2960. Cost is $157, but it's a bargain when your old one leaks like a seive from rust, and constantly clogs up its little gas filter.


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