ATC 70 power loss

[flyingatc]

Hello. My 84 ATC 70 is losing power under load, or during rapid acceleration. I changed points/condenser and timed it properly. New spark plug, cap,
and wire. Carb is new and with the proper main and idle jets 58/38. It sat for a while and tank rusted it out, so the carb had a good cleaning plus
a new plastic tank. I checked the cam timing, right on. Adjusted rocker arm to valve clearance. It starts up well and idles great. The problem occurs when i open it up to accelerate quickly or when in in gear and want to accelerate. It will bog out. If i were to accelerate slowly, then its fine. Today i ran 3/4 can of seafoam right into the cylinder. Plus 1/2 can into the tank. SAME THING! Any ideas? I am thinking compression check next?

[hillbilly 200x]

hows your air filter??

[flyingatc]

brand new "shark" air filter from dratv.

[FastZ28]

Sounds to me like your timing of the points is off slightly. My 84 70 did the same thing till I adjusted the points.

[CRAZY70MAN]

brand new "shark" air filter from dratv.

I take it that is a open filter? If your timing is correct as well as everything else you stated.....sometimes the open filters will let too much air in the mix. My 90cc atc70 had that problem. May try moving the needle clip down which will move needle up to let it have a bit more fuel at the 3/4 range. I also run a cotton sock or sometimes a rag around my filter to restrict air a bit and it runs great with it and will stumble as you said yours does without it. Are you using in line fuel filters?? Even plasic tanks need them as you can get debris in from filling now and then. Those carbs are very touchy with any dirt or particles....good luck Try the sock around your filter, if it helps you may need to jet it up or just run it with the outer sock or another foam wrap like the ones that come with the uni filters and a rubber band

[flyingatc]

Ill try restricting the air filter and adjusting clip. Complete topset including seat and holder new. I didnt check clip position though. thx

[oneroom42]

yes i deff think there is to much air with the aftermarket filters and stock jets. ike crazy70man says, these carbs are touchy. play around with it and you'll learn the feel for them!

[Vealmonkey]

Pull the plug, what does it look like? Black, tan or white? You know, a stock 70 has such low power that anything will affect it. How's your rear brake, dragging? How are your wheel bearings, dragging? How is your drive chain tensioner set? What about your clutch, properly set? The clutch could be slipping or wheel bearings dragging or chain tension improperly set. It could be a bunch of things. You have to check them all. Get a manual. Do a proper tune up from one end of your 70 to the other.

[flyingatc]

Thanks for the info. However the problem is strictly engine related, not brakes, tensioner, clutch, etc.. I tried placing a cloth around, and inside the filter no help. I
also adjusted clip position up and down..no help. I did discover something. If i place the choke 1/2 to 3/4 ON i can twist away and she sounds grrrrrrrreaaaat!!!No
boging. I need some help with this though. I am assuming that choking it closes the air flow. Therefore my problem is too much air or not enough fuel.I think mostly too much air due to the fact that with the 72 jet same issue. But how come after wraping the airfilter no help? Should i just buy the stock filter?

[Vealmonkey]

Your spark plug will tell you if you are getting too much fuel or too little fuel. Take the plug out and see what color it is. If black, too much fuel, if white too little fuel and if tan, it's getting good fuel. Why are you being difficult about this???? No one can help you by telling you what to do if you don't listen and follow their advice. Also, you didn't give very much info to go by.

[oneroom42]

sounds like a problem that i had years ago. it only ran good with the choke half on and believe it or not, the timing was off! the points are touchy and i thought i had them set right. keep us posted!!

[flyingatc]

Spark plug is normal. I do understand how to read a spark plug. Not trying to be difficult, just trying to solve a problem. The plug only fouled when i covered the air
filter. It runs great at idle and at mid power or if i SLOWLY increase the power to WOT(therefore the spark plug is normal) It only wants to die out under load or rapid acceleration. I will double check the ignition timing,valve timing,and valve clearance. I will keep everyone posted...thanks for all that are helping me out.

[Vealmonkey]

If the spark plug is "normal', then it's not a carb problem.

[Blown 331]

I know you said you timed it correctly but are you sure the points are opening far enough? If they are too narrow that will retard the timing. Point gap is actually the only ignition advance adjustment on the bike. I've seriously delt with like 50 Honda 70s that had low power due to too narrow of a point gap. I'd just open them up a bit from where you have it and try again.

[flyingatc]

UPDATE: Just wanted to keep everyone posted. Since my last attempt to get this 70 running right, i was able to get a stock air filter assembly from ebay and new
filter element from dratv. NO CHANGE!!!. It still boggs out when i open her up rapidly. HOWEVER with the choke ON 3/4 of the way its fine. I was able play with the
points yesterday afternoon. I tried making them open up a bit early, a bit late but no help. I cant believe this 70 is kicking my !!!... I actually tried adjusting these
points several times. I have the cover off and am starting the engine with a 17mm socket and drill motor. I also adjusted the clip position as to allow more fuel in at
high power range. If it is bogging out EXCEPT with the choke on. This means that its not getting enough fuel right??? initially i thought the aftermarket air filter was
allowing too much air in...Im a bit lost....