ATC 70 issues.....

[Dave's1985200X]

I did the topend of my sons 70 and took to 85cc's. I am having some carb issues. I bought this bike this winter and it needed some tlc, so I invested money in tires and a topend kit and other little things. I cannot get it to run well. It will idle nicely and when I go to give it gas it falls on it's face. I have been through every adjustmeant I can think of on the carb and still the same....... PLEASE!!! Does someone have any ideas on what I am missing??? I think it is the original carb....:crazy:

[ametzker]

If its a stock carb then I would guess the low speed jet (the smaller one is plugged). Start with the carb in hand clean the two jets in the bowl and adjust your a/f screw all the way in until it stops and then come out 1.5-2.0 turns. Put the slide in the top of the carb and adjust the idle screw so that the slide just starts to open. It should fire up and run ok at this point. Maybe just a little fine tuning.

If its an aftermarket carb then I would do that same as for the stock carb but then start adjusting your needle clip position up or down and see if it gets better or worse with the adjustment. I would try moving the needle clip up a slot so that the needle goes down in the hole further. If it just has a flat spot on acceleration and it pops or backfires then I would move it down a slot or 2. Hope this helps;)

Oh one more thing. Its possible your ignition timing is too far advanced or retarded. Try rotating your points plate to the right or left and see if it changes anything. I have had that happen before.

[RacerRichie]

sounds like timing to me. My 70 can be a pain in the ass when it wants to be.

[briano]

It could be the points or the carb, you may have to go to a bigger main jet or try moving the clip on the needle. The points may have to be cleaned and adjusted or replaced, both mine and my brother's 70 were acting the same way although his was worse than mine. I rebuilt the carb on mine and put in new points and it was great. His started to act up and we swapped the carbs from mine to his and nothing, put in new points and bingo, runs like a champ. Basically the same as you are describing they would both idle but would sputter and die when you give it throttle. 70's can be a bit of a pain to make them run right, they seem like they can always be tinkered with to make them better.

[Dave's1985200X]

Thanks guys!!! I will check the points.....