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11 Posts
Just came across the site looking for some info on my two ATC 70's.
Kids are bugging me to get them running, so here I go...
Kids are bugging me to get them running, so here I go...
ATC 70 Fix em up
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1,952 Posts
Hello and welcome! ask away!
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18,211 Posts
Welcome to the forums... I guess the first thing to do would be to determine if there is spark. if so I would drain out all the fluids oil and fuel change them both remove the carb make sure you remember how the carb to intake gasket goes pull the bowl off remove the float and needle assembly remove the main jet and slow jet grab yourself a piece of wire from a wirebrush or some cutting torch tip cleaners a couple cans of carb cleaner and get to work on the carb, be sure to remove any O-rings carb cleaner will swell them up. clean it up real good paying special attention to the jets and all the orfices put it back together install the carb do not over tighten the carb bolts they WILL strip very easily if you happen to hurcules them just through bolt them instead. now I can't remember if you remove the pull start assembly if you can gain access to the stator if so you might want to try to clean up the rust on it for cotinuity purposes. Ok that's all I think of for now good luck and keep us posted.
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11 Posts
Sounds good, that should give me enough to get started...
I just downloaded a service manual for $5 (got the thread off this site) and I'll get started tomorrow or Sat.
I figure I'll pick the best of the two to get started. I remember one of them had rust in the fuel tank and the
father-in-law tried to clean it with acid. I bought a kit a couple years ago which etched, cleaned and re-lined
the tank, but if I remember right I didn't plug the outlets very well and may need to try and open them up.
Guess I'll get to that after I get the other one running.
Thanks for the welcome and the tips! I'm sure I'll be back soon...
I just downloaded a service manual for $5 (got the thread off this site) and I'll get started tomorrow or Sat.
I figure I'll pick the best of the two to get started. I remember one of them had rust in the fuel tank and the
father-in-law tried to clean it with acid. I bought a kit a couple years ago which etched, cleaned and re-lined
the tank, but if I remember right I didn't plug the outlets very well and may need to try and open them up.
Guess I'll get to that after I get the other one running.
Thanks for the welcome and the tips! I'm sure I'll be back soon...
Joined
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11 Posts
Ok, here's the update. I started with what I thought was the better of the two. Pulled the seat and tank and checked for spark. Didn't have any spark and it looked like the problem was either the kill switch or the plug wire. Replaced the plug wire with a better one from the other bike, cleaned the spark plug real good and set the gap. Also removed the ignition coil and cleaned up all the wiring/connectors. Tried to ohm out the kill switch and didn't see any change so I clipped the ground side as the schematic looks like you ground the ignition to kill the engine and I figured I could just ground the wire to shut it off. Pulled the carb, removed the jets and cleaned real good with carb cleaner. Changed the oil, put new gas in and cranked it over. After a few pulls (and gas got in...) it started at full throttle. The problem I'm having now, is I can't seem to adjust the throttle cable. I took it out a few times and put in back in (into the carb), I tried adjusting the cable adjuster near the top of the carb but I'm not doing something right and I don't have a good diagram of the carb. Any tips would be greatly appreciated...
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38,589 Posts
there is a adjusting idle screw on the side of the carb..it moves the carb piston up and down..it's kinda in the middle of the main part of the carb..about mid ways..turn this out...and it will let the carb piston drop down..if this don't work..undo the top of the carb where the cable goes in..pull the carb piston up an out of the carb..you should see the carb piston..has a spring on it..with a long brass needle on it..while holding the top of the carb..compress the carb piston up to take the slack out of the throttle cable..it will come off the bottom of the carb piston..after you get that apart..take the carb piston brass needle..and push it up through the carb piston..the brass needle has a c-clip on it...raise it one notch at a time..careful not to drop this ..and lose it..it's a pain to find it..lol..after you raise the c-clip..put the throttle cable back through the spring..compress the spring...while putting the throttle cable in the grove in the outside of the carb piston..get the throttle cable to go all the way down the outside grove on the carb piston..until it rest in a small hole in the bottom..after that..put it back into the carb..line the piston grove with the inside notch in the carb..the bottom of the carb piston has a slant in it..it faces the idle screw on the side of the carb..after it's all the way down..from the outside of the air intake side..look to see if the carb piston is sitting all the way down in the carb throat..crank it up..see if the idle is lower...hope this helps 
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11 Posts
Sure is easy when you have the right info. The carb piston was 180 out. Adjusted the idle screw out some, re-oriented the piston and it was obvious by the throttle cable when it was seated proplerly. Started it up (had to hold the throttle open some...) and then adjusted the idle screw in until it idle half way decent. Adjusted the throttle cable so there's a small amount of play before it lifts the piston. Now I need to dial in the carb air mixture so it runs & idles smoothly. Also, the air box rubber piece that attaches to the carb is split wide open. Had a bunch of silicon gooped on it. I'm either going to replace it with a stock one or change to a K&N type. Any thoughts? Thanks a bunch for the detailed info!! :rating10: Saved me a lot of time and research.
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38,589 Posts
grats on getting it running !!..glad we could help..if you go to a open air filter like a k/n..your more than likely gonna need to mess with your air/fuel mixture pilot screw until you get it dailed in..any time you go from stock to after market air filter on any bike..it changes the whole system in the way it runs..soo..be ready to spend some time with the air/fuel mixture screw..from what i have seen and read from people working on the honda 70's..they had sooooo much trouble getting them to idle..run right with an after market air filter..soo..good luck..hope your task is an easy one !
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32 Posts
I myself have two of these beasts for my kids. One is a 86 trx 70 with a big bore 88 kit and it runs great with a K&N on it. I did have to play with the jetting some. I also have an 83 atc 70 which keep in mind does not have electric ignition but has points and those need adjusted now and then. Both of mine are fun to ride for the kids. I wouldnt put on a K&N filter on them if your going to do any trail riding cause of dirt and then you will or should rejet the carb because the K&N will let more air flow and will lean out the carb. Here is a great site to get parts from it is dratv.com. They have all you need for those 70's and thats where i got my big bore 88. CHEAP!!!
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11 Posts
Great tips all...thanks. I think I'll stick with the stock setup for now and get it running smooth. I can always tinker later on...
Time to go shopping at dratv.com....
Time to go shopping at dratv.com....
To clean that rust out of your tank,drain all the gas out.
Take ice crushed or cubed does not matter.Fill less then half way and shake the piss out of it.
This should remove the big junk.
Then run hot water to melt the ice and drain the tank.
Now take and fill the tank with vinegar,install the cap and let it sit over night.Be sure to cap the lines coming out so it will hold the fluid in,lol.
Once you drain the tank take hot water and keep filling and draining until its clear.
Almost done.
Take and fill water again and add a little baking soda to neutralize the acid from the vinegar.
Drain it and add a little gas,shake it and drain.
Install and enjoy.Its not hard at all and will get all the rust out.
Its also safer and less expensive then the chemical kits you can buy.
If you want after your done you can buy a liner to pour into it,if its going to sit out of gas for any time,so you do not have to repeat.
Take ice crushed or cubed does not matter.Fill less then half way and shake the piss out of it.
This should remove the big junk.
Then run hot water to melt the ice and drain the tank.
Now take and fill the tank with vinegar,install the cap and let it sit over night.Be sure to cap the lines coming out so it will hold the fluid in,lol.
Once you drain the tank take hot water and keep filling and draining until its clear.
Almost done.
Take and fill water again and add a little baking soda to neutralize the acid from the vinegar.
Drain it and add a little gas,shake it and drain.
Install and enjoy.Its not hard at all and will get all the rust out.
Its also safer and less expensive then the chemical kits you can buy.
If you want after your done you can buy a liner to pour into it,if its going to sit out of gas for any time,so you do not have to repeat.
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