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atc 70 running issues please help!!!!!:-)

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dnicoll

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Discussion starter · #1 ·
Hi all

I wonder if you can help?

I have had many issues trying to get my 1985 atc 70 running correctly, it boggs and seems to loose power. If you reset point it run fine for a couple of mins then start to bog again.

I have change everthing in carb, new jet, throttle needle, e.t.c. New points, new spark plug coil, new plug, checked and adjusted valves.

Im running ouy of ideas fast!!!! Please help:).
 
#5 ·
Fuel problems

You need to install a clear drain hose on the carb drain barb. Take the hose and run it above the carb. Open the drain screw. The Fuel will run into the hose and show the actual float hight. The fuel level should be 2mm below the bowl seam.

Start the machine and watch the fuel level. At idle it should not move from 2mm below the seam. If the fuel level drops the you have a fuel inlet problem.

Did you clean the petcock screen and associated parts

Electrical problems
To check running spark you can install a spark gap tool. The spark should be purple in color and have a large spark. Check your grounds. Have you checked the connection between your spark plug wire and spark plug boot. Twist off your spark plug boot cut off about a 1/4" off the wire and screw the boot back in. I have found corrosion in the spark plug boot that causes weak spark, bogging and lose of power.
 
Discussion starter · #6 ·
Thank you fastatc

Al of your suggestion do seem like logical problems thankyou.

Its so frustrating isnt it!!!!

Been thinking and was thinking along the lines of changing the condesor and contavt points retaining screw and spring washer in case the points are moving when running?

Whats ur thoughts?

Do you have an atc70? How do you find it?
 
#10 ·
Keep it up. Remember its just a toy. If your fuel is ok I would say spark. Have you replaced your points and condenser?

I have a 85 atc70 with a zx155 motor see " getting ready for the tare down thread" that is my project just waiting for warm weather to finish

I also have a 84 atc70 with a yx 140 motor running just needs paint and a 83 xmas special and that is my next project.

If you have the money and want to up the hp install a piranha 124 or 140 motor they rip and are a lot of fun. No more messing around with points
 
Discussion starter · #11 ·
Haha, yes u are rite.

I have changed the points only but will order a condenser for this weekend.

I will fit new condenser then struggle my bo****s off again re adjusting the points and see what happens.

Nice lil collection you have fastatc. Do you have any pics? You've done well to get a 83 xmas!

Taking bout changing engines there is a atc70 with 250 2 stroke on youtube WICKED PIECE OF KIY!!!
 
#12 ·
I saw the 250r atc70 pretty wicked. Trust me all you need is a zs155 with a 192 big bore kit. The 70 in the tare down post can do 3rd gear power slides on wet tar. And top out at 60mph.

I have a 1 1/2 frame stretch, 192cc motor, foot brake and working on front suspension right now.
I had to rebuild a stock motor and it needed a crank. I picked up a 140 motor replaced the coil and modified the pull start. The 70 has tons of power and runs great never a hiccup and never having to mess with the points is the best part
 
Discussion starter · #14 ·
Hello again everyone.

Rite i have changed the condenser and mested around with the carb settings and can get the bike to tick over and seems to run fine.

I can ride it up the road and go through the gears.

When i have been riding for 5 - 10 minutes the bike seems to loose power and will not start again. I can remove plug and cool down and off we go again!!!!

Is my plug the issue? Is it overheating?

Look forward to ur comments
 
Discussion starter · #16 ·
What wad happening was the ht lead on my new coil was coming loose at the coil end under the tank!!!

Changed the coil, readjusted air fuel and now runs as it should :).

All i need to do now is clean the fuel tank.

Had a decent run out of it and goodness me its fun!!!!!
 
#17 ·
If the tank is not too bad you can pour in ball bearings into the tank with acetone and shake the tank. It will free up all the junk and when you are done install a good fuel filter.
You can use air rifle BBs. They are cheap and work good.
 
Discussion starter · #18 ·
Thanks fastatc

I used the existing fuel in the tank, added some small nuts, bolt and washers. Shake well and flushed out with fresh fuel a couple of time untill it run clean.

Replaced tank and filled again with fresh fuel.

It now runs a treat, fires on first pull and runs really well.

I have noticed that the gear selecting seems to loose sequence if you are not carefull with the selection. Am i doing something wrong?

How are ur projects coming along fastatc?
 
#19 ·
About the gear selecting. Try changing the oil. With the auto clutch oil gets contaminated quickly. It may help!.

I will be working on the x mas special, getting the motor back up to par. I think I will replace the crank with a xr70 crank and do the cdi upgrade. I have the tank cleaned so I can get the right color blue.

I have a Yamaha worrier to rebuild for a friend before I get to my projects
 
#20 ·
And about the shifting problem you can adjust the auto clutch. It's been a while so I will have to read about it. I think you lessen the clutch nut turn the flat head screw cc's until you get tension then do a 1/4 turn back.

Some one on hear may know or have a service Manuel on proper procedure
 
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