Atc 200x blowing gray/black smoke?

[Atc 200x 1985]

I’m stumped here. I have an 85 200x with Mikey's upgraded 30mm carb, but the stock exhaust. He said it was fine to run the stock exhaust on it. I plan on buying a new pipe later, but my question here today is. Why Is it running so rich? I guess it's running rich. Usually, black smoke means rich, blue means oil, and white means coolant, but that's literally impossible since there isn't coolant, lol. It fouls plugs, but every three-wheeler I've owned does it. When I got the carb about six Months ago, it had a 110 main. It ran rich, which is odd considering the carb's throat is bigger, but now it bogs if I slam the thing to full throttle. I've taken the main down to a 100, and it's still doing it. Do I need to go lower? Do I need to drop my pilot jet size? Am I missing something here? The only other things done to the engine are a 12-1 wiseco piston and the carb. Another thing I notice while idling is that it seems like there is condensation building in the exhaust??? You can visibly see water droplets at the end of the exhaust.

[shortline10]

Wiseco pistons are known to smoke , their 200x piston rings suck IMO especially when you ask them to seal a 12-1 compression piston .

Their are obvious differences in the smoke , easiest way to tell is if it smells like burning oil it’s rings and if it burns your eyes terribly and smells like excessive fuel it’s a carburetor / fuel issue .

[Atc 200x 1985]

Gotcha. It doesn’t smell like burning oil, but I could be wrong, and it could be burning it much worse than I assumed. I’ll try that eye test; if that fails, what rings should I get?

[Scootertrash]

I always go back to the basic jetting procedure:

https://www.3wheelerworld.com/showth...Jetting-Theory

You can guess, then throw parts at it....ask here and have others guess, then throw parts at it, ask on other forums and have them guess, and throw more parts at it......OORRRR!!

You can save time, money, and frustration and start from scratch, because almost every build, especially custom/high performance builds...are gonna be different, if even just slightly different.

Every three wheeler you've had has run rich?? I can't remember ever having that problem, but I'm pretty picky about dialing in my carbs. If any of mine were running rich after tuning the carb in, it was so slight I couldn't notice.

[ATC King]

A weak ignition will never be able to be tuned for.

A weak ignition is made worse with higher compression.

An engine with a weak ignition may still start easily enough and run okay, but it'll never properly ignite the mixture for a complete burn and will likely break up at higher engine speeds and loads.

It's common to see on worn engines that get a new ignition to start smoking. They were burning/loosing oil before, but it wasn't being thoroughly combusted and with a properly functioning ignition, the smoke is obvious. Not saying you're engine is worn, it's just an example of the difference a good ignition can make.


Having the sparkplug outside the cylinder and looking for spark is no more an indicator of it's energy than sticking a finger into the hole and seeing if it's blown out at TDC and saying that compression is good. Without quantitative data it's all just spiting in the wind. Unfortunately, there's no spark energy baseline for ATC engines that I know of off-hand, which makes it difficult to know where to start or to test a questionable ignition.

If it's a 40yo electronic ignition component, it's not as strong as it was when new. Run time doesn't even count here, it could be NOS, but the components are still degraded. The saving grace is a 200X has a mechanical advance, so it's not like a modern programmable ignition is needed, but they do save time versus fiddling with weights and springs. A performance build will not run properly or to it's full potential with a stock ignition and a preprogrammed 'performance' ignition isn't some magic bullet. Ignitions need tuned the same as a carb if it's all to work at it's best.

You may be able to use one of those cheap spark energy testers from Amazon or Ebay but you'll need known good data to compare it to. I think someone may have posted that on here, sometime ago, so search for that. What a cheap tester like that will tell you is not the same as something that measures spark energy on a running engine, but with good data it'll tell you enough. Load changes how much energy the ignition makes, they don't just dump everything they're capable of, just what's needed to jump the gap. It's like with engine HP ratings. They're not making that at idle or part throttle, that's the maximum they make, at maximum effort.


BTW, are those water droplets or fuel? If you're running the stock airbox, check that the air path through the frame isn't obstructed. Also, you've always had poor running machines if they foul plugs. I feel like if you ever had a good running stock machine, you may not have seen a need to try and increase power. A top condition stock engine that's tuned and runs clean everywhere is way more fun to ride than something built that only cleans up a WOT.