DG Exhaust For 1981 Honda ATC 200 - Jet questions

[Pierce1989]

Hey everyone, hoping someone could help me here. I just installed a DG Performance 04-2106 - RCM Steel Exhaust on my '81 200. After having to make a dent in the header pipe where the front frame bar is, it finally fit enough to install (read this on another thread). I know how to clean carbs but have never rejetted one. I cleaned mine and have been messing with the air mixture screw and idle screw but it still doesn't sound right and I have black soot on the spark plug immediately when running WOT and checking right after.

Has anyone changed their jets with this same setup and what did you buy? Everything is stock besides the new exhaust. I have read threads about the jet sizes people have bought but it's a little confusing and it seems like you could buy one, it doesn't work, then you have to buy another one to try. Hoping someone has some advice that will get me back out in the Everglades sooner than buying/returning jet sizes to see which one's best!!! Thanks in advance

[ATCKevin]

A black sooty plug is a clear sign of a rich condition. I have the same exhaust on my 86 200s. I'll start with telling you my experience with that. Usually exhaust modifications or intake modifications require jetting changes to compensate for the added air flow. I have access to a chassis dyno with fuel mapping software so I put my trike on it and mapped my air-fuel ratio on it. To my surprise, I was still running rich after putting the exhaust on. So if you're suspecting a rich condition on your trike, start with your main jet. See what your jet size is and see if its stock. You should also look at your pilot jet and see what the clip setting is on your jet needle. I recently had a john deere gator in my shop that was running very rich. It would soot and foul a plug within minutes. There was only one smaller jet available for the carb so I bought it. 85 was what I had, I bought an 80 figuring it was gonna be too small. I suggest buying a set of tip drills if you're worried about buying jets just to try them. I started with the 80, and kept drilling out the hole until it sounded like it was running good. Did a plug chop on it after a long drive and it was good to go. Thats just my two cents on the whole buying jets just to try scenario. You can find those drill bits online or at a tool store usually. I got mine off the Mac truck when I worked at the Deere dealer.

[Pierce1989]

Thanks for the response! I will try that. I was under the impression people buy one size, it doesn't work, then they have to buy a different size and wait for shipping. I didn't know I could drill one out until it's just right. Thanks again!

[ATCKevin]

Well thats not the perfect and proper way to do it, but it does work just fine if you're not wanting to buy jets just to try. But you have to be patient. If you go too big, you're back in the same boat!

[Pierce1989]

Thanks! I'll never learn without this so here's my dilemma, I have 2 ATCS now. I've had an '81 Honda ATC 200 I put the '81 exhaust on recently for 4 years, and picked up another '81 Honda ATC 200 in Naples last week just because I love 3 wheelers. The one I have the new exhaust on has a Keihin carb PD 35CA3J (and another last digit I can't read). This carb's pilot jet has no screw at all. Is this normal? It's just a hollow tube where the pilot jet would be, but no slot to unscrew it. The new ATC I bought has a main and pilot jet than can be unscrewed, and is a Keihin PD 35DWWG (and another last digit I can't read). They run but the one with new DG exhaust fouls the plug, and to get it to run the air/fuel mixture screw isn't the recommended 2 - 2/12 screws out. After looking at main jet prices, they're a lot cheaper than I though. $3 - $6 dollars each. What sizes do you recommend if I bought 2 to accommodate for the new exhaust? The main jet I have in that one is #105, and pilot jet can't be unscrewed... Thanks again!!

[Pierce1989]

Anyone?!?! I just messed with it again, dry black plugs every time. It is idling and running, and the mixture screw on bottom can be at a wide range. I figured it's running rich with the dry black sooty spark plugs, screwed the mixture screw all the way in to make it as lean as possible, did a plug chop with a new plug and it was still dry black soot. If the main jet is a 105 Keihin, I was going to order a 100, 102, 108, and 110. Or is this excessive? Since the only has a pilot jet tube with no pilot jet to unscrew, I was going to leave that as is. What do yall think? And has anyone seen that carb without a pilot screw to unscrew? I have 2 ATC, same model, carbs look the same, but one has an unscrewable pilot jet and one does not! Please, any advise is greatly appreciated!

[ATCKevin]

I cannot picture one of those carbs not having a removable pilot jet! got any pics?

[350for350]

I have one or two of those myself. I couldn't believe it when I first saw that you couldn't unscrew the pilot jet. I did take one out by grabbing it with a pair of Vise Grips and twisting and pulling on it at the same time. It didn't have any threads either. I sure that it was just a press fit.

[jb2wheels]

Way back in the 80s I had a 185s. I added a Bill's pipe. It needed to go leaner. I could not believe it. I do remember my dad told me repeatedly to try a leaner jet because he had a similar issue with an old Roundtop once.

Anyway, when I have to make jetting changes, I like to buy a handful of jets around the size I currently have - 1 or 2 leaner, 4 of 5 richer - and pay shipping once.
I prefer to buy from JetsRUs - not the Amazon jet kits from unknown sources and questionable accuracy.
I don't drill jets.

Then you have to ride it and see how it performs. Ideally, you'd have a nice long stretch of road to do top gear pulls and (using a tach) see which one pulls the most RPM (or MPH I guess) - but that's not usually a reality for ORVs.

[Pierce1989]

I cannot picture one of those carbs not having a removable pilot jet! got any pics?

Here it is! It's bizarre to me as well.

[Pierce1989]

Way back in the 80s I had a 185s. I added a Bill's pipe. It needed to go leaner. I could not believe it. I do remember my dad told me repeatedly to try a leaner jet because he had a similar issue with an old Roundtop once.

Anyway, when I have to make jetting changes, I like to buy a handful of jets around the size I currently have - 1 or 2 leaner, 4 of 5 richer - and pay shipping once.
I prefer to buy from JetsRUs - not the Amazon jet kits from unknown sources and questionable accuracy.
I don't drill jets.

Then you have to ride it and see how it performs. Ideally, you'd have a nice long stretch of road to do top gear pulls and (using a tach) see which one pulls the most RPM (or MPH I guess) - but that's not usually a reality for ORVs.

Thanks, that is what I am going to do as well. If I know it's running rich even with the pilot screw screwed all the way in, would you reverse that order? 1 or 2 sizes richer , 4 or 5 sizes leaner? If my explanation even makes sense with it running very rich even with a new exhaust and pilot screw all the way in. I am going to check the electrical as well, maybe weak spark?

[Pierce1989]

Thanks, that is what I am going to do as well. If I know it's running rich even with the pilot screw screwed all the way in, would you reverse that order? 1 or 2 sizes richer , 4 or 5 sizes leaner? If my explanation even makes sense with it running very rich even with a new exhaust and pilot screw all the way in. I am going to check the electrical as well, maybe weak spark?

Also, this trike will not run with the choke on/closed even before the new exhaust. The bike always starts right up with the choke off/open. I would assume it's always ran extremely rich already and when I put the choke lever up to reduce air, it becomes way too rich. Any advise on this? Would a couple-sizes smaller main jet lean it out and fix this so I can warm it up with the choke closed like everyone else and then switch it down to open position, or does this sound like a different issue?

[350for350]

I'd say that you'll definitely need to go leaner. For some reason, I'm thinking that a 95 main jet is what should be in there from the factory. If that's the case, then it's running rich with the 105. I don't think I'd go any richer. If all you did was add the exhaust, then I'd try a main jet that's around a 98 to a 100.

[Pierce1989]

Great point 350for350. Both the trikes have 105 main jets for Keihin PD35C and PD35D and didn't have any previous mods , and the one with the unscrewable pilot jet has a #38. I didn't consider the main jet could have been changed on both the trikes by the previous owners, maybe increased for mountains or lived up North... which there's no need for in South Florida. Thanks so much for the help!

[350for350]

It's hard to tell what may have been done in the past. You use a smaller jet size for increased altitude. That way you get less gas to mix with the thinner air.