ATC90 rebuild

[bigcal]

I picked up this 78 ATC90 a couple months ago for my kids as my 9 year old was ready to move up from the 70. Here is a couple pics before i started and what all transpired.



It was pretty cheap, even with how it looked so i figured what the heck. I ended up having it delivered because I could not go look at it right away and the owner was passing through town in a couple days, and it was located a couple hours away. The PO started it for me when we loaded it, but i could not get it started after getting it home. Well it turned out to be a basket case... I removed the plug to check for flooding/fouled plug, and the threads were stripped in the head. So I pulled the head to fix it or replace with ebay head. While i was there, i check the cylinder, it was scored so i pulled it off, the top ring was broken and piston scored so i removed the piston and the con rod was scored badly.

So since I am a glutton for punishment and I enjoy bringing things back to life I decided to do a complete rebuild. Chain had been thrown and busted the case, sprockets and chain junk. axle bent. clutch release mechanism was welded solid, broken gear in transmission. crank was junk from scored rod, and severely worn down inside clutch bushing.

I installed a good crank with new bearings, new piston with bored sleeve, different head with new valves, clutch release mechanism, different transmission gear assembly, better clutch all inside a good set of center cases. new direct bolt sprocket, oe rubber mount was junk,new chain and front sprocket, different axle. Switched out the tires for some matching ones i had. New DG exhaust, oe one was welded in a spot and found holes inside frame. new rear axle bearings and seals.

Long story short, besides the new seat cover, which by the way was a real pain in the butt to install, it looks about the same but purrs like a kitten. My boy took it for a test ride last night on his birthday, and was real happy. So my cheap buy turned into an expensive project, but I know what i have and it should last another 37 years. I have a few small items to address, no lights atm and some cosmetic things i would like to improve and then i will post some pics. Would like to have just done a complete restore but time and money are squeezed pretty thin right now.

thanks for looking

[bigcal]

many thanks to all who have posted on this site, and for hosting the manuals online. I have been reading this forum for years but decided to join this being my first atc rebuild.

[shortline10]

Great job .......

[81ATC185S]

Good to see you brought it to life. I like reading these posts about people fixing garbage trikes. Makes me happy that the stuff I have is actually decent. I have a 77 ATC 90 I bought for 110 bucks and it needed some stuff so I bought a parts bike for 300 bucks. First ride both compression rings seized in place so I swapped jug and piston from my parts engine and she purrs as well. It runs really bad inside because I have it tuned for the -40C Canadian winter. Take her out side in the cold and she purrs really nicely. Im 5.8" and 200 pounds and my 90 hauls me around through 1 foot deep snow in either high or low. I gotta pull the engine again and put new gaskets in. It was my second engine I tore down in my life and I thought I could save a buck by reusing the gaskets, but they leak bad so I ordered new gaskets.