After many yrs. of not using it, I started my atc 70 a week ago. I replaced the points, got a new gas tank, new air filter and spark plug. It started ok, and ran well, i could just not get it to idle. After a few days, it started to backfire and now it will just not turn on. I just replaced all of the carb parts today because the old o-rings were leaking and wanted it to have new parts. It still sparks. Could the points have loosened up and need to be reset or would there be no spark if it was not set right? Is there a setting for the screws on the carb? If so could someone tell me them? Not sure what else to do, any suggestions? MANY THANKS......

 

The backfire is a sign of lean. When you had the carb apart...did you remove and clean or replace the pilot jet?

 

i replaced all of the parts of the carb about an hour ago. Is the pilot jet the one inside in the middle, the bigger one? If so the one I replced it with has a big hole in the center compared to the original one. Should I put back the original one?

 

The jet should have been the same size, as the original. If the old jet is clean, on the inside diameter, Id reuse it.
The pilot jet is off center. The slide needle and main jet are inline, the pilot jet is offset from them.

 

The opening on the pilot jet for that is sooooo small and clogs so easily. It is the longer thin one. The main jet is the short wide one. They have a number on them, make sure the new ones are the same. Is the inside of your tank clean? Now is a good time to rinse it out. I dont remember the mixture screw stock setting but I have a manual at home I can look it up. Or you can download one here:

http://www.glamisdunes.com/inv...ndex.php?showforum=50


Lots of good 70 info.

 

<div class="FTQUOTE"><begin quote>Originally posted by: scary132


<a target=_blank class=ftalternatingbarlinklarge href="http://www.glamisdunes.com/invision/index.php?showforum=50
">http://www.glamisdunes.com/inv...hp?showforum=50
</a>


Lots of good 70 info.</end quote></div>

Hey, that is a good site [img]i/expressions/face-icon-small-smile.gif[/img]

Mixture screw is generally about 1 1/2 turns out

The main jet should be a 58 that is the small round jet
the number should be stamped on the top of that jet.

The pilot is a 38

unless you have done modifications to the engine I would not deviate from those jets sizes.

Also check the screen behind the fuel shut off valve, it probably has rust in it.

after you have cleaned your carb install inline fuel filters to protect the carb

Tres

 

<div class="FTQUOTE"><begin quote>Hey, that is a good site </end quote></div>


I think you may be biased!

At least once in my life I need to make it down there.. hopefully for the Regatta!