ATC 70 Fouling Plugs [Archive]

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branstetter412

03-26-2011, 02:49 PM

I bought a really nice looking 1984 ATC 70 about a month ago and am having a problem. It runs great, has plenty of power and looks almost brand new, however, it starts to smoke "a little" after the engine runs for 3 or 4 minutes. Not a ton of smoke, but enough for me to notice. I can't tell if it is blue smoke or dark smoke like I have heard other people talk about. More like white/grey colored smoke. I have replaced the spark plug twice now and have only run the engine for about 6 or so hours total. It seems to foul the plugs when I am starting it. It will start to fire up, die, and then won't start again. When I pull the plug I notice some blackish liquid (oil/gas) around the hole where I pulled the plug. And the spark plug itself is very black around the end, but smelled like gas. I just put my third plug in it and it is running great (still putting out some smoke) and this plug came from a Honda dealer, it is a different NGK number than the ones that came with the bike, so I am hoping it was just the wrong plug, but I got a feeling it is more than that. As you can tell, I am no mechanic, but a friend told me it might be the rings? Any help or opinions are appreciated.

Ron Branstetter
St. Louis, MO
ron@bigheadron.com

shortline10

03-26-2011, 02:58 PM

Sounds like its time for a top end rebuild . Does it smoke all the time or just on start up ?
Are you getting a nice fat spark on the plug ?

tri again

03-26-2011, 04:44 PM

I've got a few like that.
Like to foul plugs.

I also have a few that smoke real bad OBvious oil burners that do NOT foul plugs.

I go thru the carb.

slo jet may be plugged and someone compensated by raising the main needle???

haywiremechanic

03-26-2011, 06:26 PM

I would suggest you check the crankcase breather and be sure it's not plugged. If it is, pressure can build up in the crankcase and cause oil burning like you describe.

I have seen crankcase breather tubes plugged solid with some kind of insect mud nest. Not sure just where the breather is at on an ATC 70.

A compression test will tell you for sure if you need to rebuild the top end.

Test your spark. It should jump a 1/4 inch gap at cranking speed. If not, clean and gap your points and check/adjust the timing. On an old-school magneto ignition, a weak spark is usually caused by dirty points, in my experience.

As already suggested, clean and adjust the carb. From your description of symptoms, it may be running too rich.

oldtime3wheeler

03-27-2011, 07:41 AM

My one 83 used to eat a plug here and there. I have had similar problems with it. I found that if I change the gap in the plug and make it a little smaller that the freshly killed plug will work again. Its not the solution, but a quick fix.

1984 honda 200s

03-27-2011, 11:34 AM

clear smoke on a cold day is just condensation or vapour....if it just does it on start up/warm up for a min or 2 then its normal. if its DARK smoke your running to rich. if its blue its burning oil.

branstetter412

03-27-2011, 01:12 PM

tri again

03-27-2011, 02:15 PM

Thanks guys for all your help. I will let you know what I find out as I dig into this further. I am ashamed to say that I just checked the air cleaner today and it was a complete mess. Basically was in the process of complete disintigration. I cleaned out the housing and orderred a new foam filter. Wondering if this might have something to do with my problem. Thanks again.

Yeah, if they get that sticky and melt and crumble, it could be like having the choke on.

I'll prob get yelled at but it seems like all my trikes will run good with no air filter..
ya know, just to get them running.

Air filters seem more important for the fine tuning/carb mix adjustments
and of course, dirt prevention.

but imo, they should run pretty good without..maybe a little lean.
so clogged, they should run rich.

Sure hope that's it for you.

Any mice or bees nests in there?