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Thread: 1984 ATC 200 not idling and backfiring

  1. #1
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    1984 ATC 200 not idling and backfiring

    I just bought a 1984 Honda 200s. The problem I am having is once it warms up it won't idle. It also backfires through the exhaust on deceleration. It starts first pull on half choke every time and idles okay until it warms up. Once it warms up it also has a bit of a hanging idle after the throttle is blipped, but after a few seconds the idle will drop very low and eventually stall.

    So far I have put a new plug in it and took apart the carb and cleaned it. I have the fuel scew set to 3 turns out from closed right now and have tried playing with it but it doesn't seem to change anything. Any ideas on what is going on here?

  2. #2
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    Sounds like its running too rich with the backfiring, the hanging idle could be part of that as well. How did the plug look? Was it black and wet or? Reading the plug is a surefire way to know whats going on in a motor.

    I would say you still have an issue in the carb, did you pull the jets and really go through it, blowing compressed air through all the passages and soaking it good? I have had to let them sit in a can of carb dip for a day or two sometimes to clear out the passages when they get really bad.

    The mix/pilot screw is about 2 1/4 turns stock, get it idling and let it warm up, then turn that screw in which is clockwise very slowly until the motor dies, then turn it back out counterclockwise one turn. That should be about perfect on them. The hanging idle once its warmed up could also be an air leak, i fought that for a while on one, it was the o-ring between the carb and the intake, since you had it apart and cleaned it, did you replace that o-ring? They get flat and hardened with age. There is also an o-ring between the intake and the head. The carb kits usually include both of those as they are generally a problem after removing a long time installed carb and they won't seal back up. Pretty common problem.

    Also make sure the needle has the clip in the third groove and check the area of the slide where the stop screw hits it, a lot of people will adjust the idle stop screw with the slide rested on it, that will create a dent in the metal a lot of the time that causes it to hang a bit. A dremel tool with a cutoff wheel works well to polish the bottom of the slide notch smooth again and the just clean up the end of the stop screw if needed. What i generally do to adjust idle is give it a little throttle to bring the slide up off the screw then adjust it and let it drop back to idle, haven't dinged one up yet.
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  3. #3
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    I had a 200s that the idle was real erratic. It did about the same thing yours is doing from how you described it. Some times it would run great, the next time it would idle about 1/4 throttle. No amount of carb tuning could fix it. The carb was junk. only way to fix it was to replace it.
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  4. #4
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    Slide needle and brass seat are worn and possibly the pilot jet half clogged . I have also see when the stator is starting to fail it doesn't supply enough spark and acts like a carb issue .
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  5. #5
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    The plug is black and wet. And it fowled one the other day. So I think you guys are right about it being a carb issue. When I cleaned it I did take out all the jets and blew air through the passages. However I didn't let it soak in carb cleaner overnight I just sprayed some through it. Does anybody have experience using the cheap Chinese copy carbs for these motors? They are pretty cheap on eBay and I was thinking about replacing my old carb with one.

  6. #6
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hello


    I just bought a 1984 Honda 200s. The problem I am having is once it warms up it won't idle.


    Typically rich on pilot jet or mix screw too rich

    xxxxx

    It also backfires through the exhaust on deceleration.


    Typically exhaust leak at head pipe, lean pilot or leaking fuel into engine from high float level.

    xxxxx

    It starts first pull on half choke every time and idles okay until it warms up.


    Typically rich on pilot or mix screw or high float level if it’s around 55 degrees or below. It should require full choke at 55 or below.

    Xxxxx

    Once it warms up it also has a bit of a hanging idle after the throttle is blipped, but after a few seconds the idle will drop very low and eventually stall.


    Hard to say in your case

    xxxxx

    So far I have put a new plug in it and took apart the carb and cleaned it.


    Did you spray carb cleaner in holes and watch it come out in the carb body?

    xxxxx

    I have the fuel scew set to 3 turns out from closed right now and have tried playing with it but it doesn't seem to change anything.


    Idle circuit plugged or too rich, set it to kb's spec.

    Xxxxx

    The plug is black and wet. And it fowled one the other day.


    Rich from jets, high float level, leaking needle and seat or weak spark.

    Connect clear plastic tube to drain on carb if you have one, hold tube above carb ooen drain screw. Gas should be around 1/8”-1/4” below where bowl and body meet.

    Lay plug on head cold and check spark

    Check spark when warm

    What color is spark and is it strong and clearly visible?

    Does spark get weak when it is hot?

    Is slide tight in carb in does it have a lot of play?

    Xxxxx

    Does anybody have experience using the cheap Chinese copy carbs for these motors? They are pretty cheap on eBay and I was thinking about replacing my old carb with one.

    Amazon has them also, they seem to be ok but occasionally require jetting, try all the tests in yours first.

  7. #7
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    One thing I forgot to mention is the small o-ring that is on the fuel screw was ripped when I took the carb apart so I don't have one in there. Also there is a bit of an exhaust leak where the head pipe meets the cylinder head. Is there a seal a can replace in there? I have checked the spark on a cold motor and it was strong but I will try it on a hot motor. And yes when I cleaned the carb I sprayed cleaner through all the passages and jets.

  8. #8
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    You can leak air past that scrrw which may cause irregular idle, it may also drip fuel you need another one, they come in an oem carb kit, vut mnmayne not in the moose racink kit.

    This can cause a slightly rich condition.

    Do the clear plastic tube gas level check, I wouldn't waste my time trying to jet until i did that and fixed the screw.


    Like i mentioned the ex leak is guaranteed to cause a pop, you need a copper crush gasket, go to a honda dealer they should have one to fit or go to an industrial hardware store and ask for copper crush gasket, you will need to know the outside diameter.

    The missing o ring may contribute to popping also sometimes.

  9. #9
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    Thank you Barnett and everybody else for taking the time to give me some advice. I'm going to try everything you have recommend. Hopefully it fixes my problem and I can start riding!

  10. #10
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    I just did the tube test and the gas is 1/4 inch higher than where the float meets the bowl. How do I adjust this?

  11. #11
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Quote Originally Posted by ssrider View Post
    I just did the tube test and the gas is 1/4 inch higher than where the float meets the bowl. How do I adjust this?

    Hello


    OK, Great, your gas level is so high that it is causing your bike to run rich everywhere. As mentioned you must fix this before trying to jet it may fix all your problems. Your needle and seat sound ok otherwise gas would be coming put your overflow hose.


    1. Remove float bowl, hold float up gently so needle is closed, turn gas on and see if it leaks from needle just to be sure it is good, don’t smoke while doing this. You can also turn carb upside down and blow into fuel line and listen for air.


    2. With carb upsidedown, measure distance from float to carb gasket area. Bend tab that pushes on needle until float is proper level per manual or just adjust them so they are 5/16 lower than they currently are.

    OEM MANUAL FLOAT LEVEL SET TO .55” Pg 49
    http://www.kb0nly.info/ATC/index.php?dir=ATC200S%2F


    3. Reassemble and do plastic hose test again, once gas is slightly lower than carb body you should be good, see how it runs and report back.

    You are actually the only person I have suggested this to that has done it and it is recommended in the manuals, go figure.

  12. #12
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    Thanks for the service manual. In there though it says if your float level is out you have to buy a new float. I noticed the tab that pushes on the needle is plastic, whereas other carbs I have seen are steel. Can you still bend the plastic?

  13. #13
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hello

    Hello


    OK, great...not. You now MUST measure it like I mentioned, use a narrow tape measure or a 3/8" x 2" piece of manilla folder. Simply put a mark at 5" and hold it next to float while end is resting on carb base minus gasket then simply look at it from the side, easy deal. If it's like 1/4" off you need to bend it or get a new float, if it is only like 1/16" off it is ok. It should not have changed from orig and may be ok however that's a high level in the clear plastic tube test per one of the manuals.

    Did you do the needle and seat test? You must do ALL these things or you're just wasting your time and might as well park it.

    To bend tab on float if necessary it's tricky and if not done carefully will bend entire float out of wack and you will need a new one. Place float on ground, take a 3" x 3" piece of cardboard and cut a 1/4" wide by 1/2" deep piece out of it along one edge between the ends so the plastic tab only will be exposed when you lay it on top of the float. Point hair dryer away from float and heat tab area only. Heat a little then try then heat some more and try. When it is warm enough it will bend with lite pressure using needle nose pliers to twist it, if you just push on it the plastic shaft might bend down, not good, hold it in place until it cools. You can also do this with the steam from a tea kettle, really hot water or holding the tip of your soldering iron around 1.4" away. It will heat quickly doing this though. Best of luck.

  14. #14
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    That measuremeant was obviously .5" [1/2"], lol.

  15. #15
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hello

    Here's another much safer, faster and easier way to cheat on the float height and it is easily reversible. Go to an industrial hardware supply store [maybe home depot] and get like 6 fiber washers that fit over the threads on your brass seat for the needle. Simply install two of those and recheck height, this should change it by around 1/4". Use more or less as needed.

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