1989 dt200

[oldcobia]

Am having some issues with my motor. Had some bogging problems but then cleared up. Was looking at carbs and noticed a small hose was off at bottom of lower carb. Pulled off oil tank and noticed that one of connectors to the oil pump was cracked. Then saw that a small adjustment screw on port side of lower carb was out farther then the other two carbs. I see in service manual the amount of turns out for the carb setting is 1.5 to 1.75 turns out. Is that for the pilot jet on starboard side or this adjustment on port side? Which is which and how are they set? What is the purpose of the small hose at bottom of lower carb? Can someone tell me it is for. Have not been able to find out on line. Thanks

[Solarman]

First off you have 3 carbs. Each of your carbs is basically 2 carbs. So each carb provides fuel and air for its respective cylinder, the bottom double carb takes care of the bottom two cylinders, the middle dbl carb the middle 2 cylinders, and top carb, the top cylinders.

Now, look at each cylinder's plug(s). Don't mix up the plugs, keep them in order to know what cylinder they are from. Can use a cardboard box top, punch holes similar to where plugs are. At the top lable one port, and the other starboard, as you remove a plug put it in its respective hole in the cardboard. Now once they are all in the cardboard you can compare how each plug is firing in each cylinder. Even take a pic to post if you want.

Each plug should be a light choc/tan color. A dark chocolate/tan color (getting black) indicates its carb is too "rich". This means that mixture screw on that carb for that cylinder is screwed slightly too far in (closed).
Now, if the plug color is too white, this indicates that mixture screw is slightly too far out (that cylinder is running too "lean").
A lean running cylinder could backfire at idle, burn too hot at higher rpms, plus can burn a hole in that piston. This should be corrected. A rich running cylinder will load up the plug, but doesn't normally harm anything, though you may need to clean or replace plugs more often.

All of your mixture screws should be set at what the service manual recommends. If the manual says 1.5 - 1.75 turns out, then turning each screw in until out is lightly seated and back out to the recommended setting. You should count the number of turns in for each of the 6 screws and write that number by its respective plug(s).

If the color of the plugs are good on any cylinders, those screws might be the proper number turns out. You can skip those, or check them, putting them back how they were (they should be proper number of turns out.)

And last, if any cylinder mixture screw is properly set, but plug(s) are burning poorly there could be a problem with that particular carb. It may need cleaning, or have another problem.

You also have a primer solenoid system that acts like a choke when you first start up, if this is malfunctioning it too can load up the plugs?

Not sure what tubing you are mentioning?

Good luck, hope this helps a little, post back when able to let us know how it's going.

[oldcobia]

It slipped my mind that these where 2 barrel carbs so there is an adjustment screw in each side of carbs. Am I understanding that more turns out means leaner and in is richer? Can these be adjusted for best idle or stick with recommended turns out? I will check plugs for color after next run. The hose I am asking about it a small hose that comes from under the flywheel and attataches to a fitting on the bottom of lower carb. Thanks for your input.

[Solarman]

When you adjust mixture screws out, that adds more air to the preset amount of fuel, this is leaner.
When you adjust mixture screws in, that closes the air pas-sage down, less air causes richer mixture.

I don't see any tubes in parts list except the primer tubes, fuel lines, and oil lines. The primer tubes go to the base area of each carb. It looks like the top and bottom tubes go to the primer system, and the middle carb is fed from a tube off the bottom carb.

If any of these primer tubes are disconnected, this could allow an air leak at the base of carbs, causing a lean running motor. Poor idling condition on all cylinders.

Good luck, post back when able to let us know how it's going.

[Hoosmatroos]

@Solarman mixture srew in is leaner en out is richer. Small mistype?

[Solarman]

Not true. Screwing the mixture screw in cuts off more air causing a richer (more fuel) mixture. The fuel flow is the same, the mixture screw controls the air mixing with the fuel at idle (screw in - less air, "richer" / screw out - more air, "leaner").

Hoosmatroos, i encourage you to help, but please be accurate when offering help.

Thanks - Ralph

[oldcobia]

Got everything put back togrther and seem to work fine except at idle it seems to make a sneeze like sound fairly regular. Also found a mismatched idle screw on port side of lower carb. Thanks for all input.

[Solarman]

Did you set all mixture screws identical, book setting? Lightly seated closed, then turn each screw out the required number of turns to book setting.

If still a sneeze and all carbs are cleaned, all pas-sages, jets blown out, then turn one screw on only one cylinders/carb 1/16th turn in, let idle for a good minute. if no change to sneeze after that minute, return that screw to its previous position, and do the same thing to the next cylinder/carb, always returning to original position if no difference. Do each cylinder/carb until all 6 cylinders are tweaked 1/16 turn.

(Sneezing, is commonly related to a lean mixture, if carb pas-sages are thoroughly cleaned, and there are no air leaks at base gaskets, then tweeking the mixture screw for that one cylinder is ok.)

If sneezing persists on multiple cylinders (same carb for those cylinders - both top, both middle, or both bottom), there is a good chance a air/fuel pas-sage is still not cleaned out completely.

Good luck. Post back how its going when able to let us know what you find.

[oldcobia]

Thanks for the info. Will get to tweeting it next weekend. I need to get it out of water and on muffs. Too difficult to do while in water. I also have ordered replacement pilot jet for lower port mixture screw. Had to go to another source for part because Boats.net does not list a 1989 DT200 for parts. Even called to make sure. Thanks