80 c.c runs best on half choke..whats wrong ?

Discussion in '2-Stroke Engines' started by rumme, Jun 12, 2008.

  1. rumme

    rumme Member

    does this mean I need to lower the needle clip / raise the needle in the carburetor one notch to allow more gas in the carb > ? I did modify the muffler by cutting out the inside baffle rod....leaving only 2" of rod inside the muffler.

  2. If you need to close the choke, you probably have an air leak at the intake manifold. To check you can spray some WD40 near the area while the bike is idleing, if it revs air leak.
  3. rumme

    rumme Member

    no air leaks...already checked.....
  4. Then the clip on the needle needs to be lowered to raise the needle to allow more gas so that the choke can be opened. More gas = more air, so raisnig the needle should allow you to open the choke all the way... What position is the clip on now?
  5. rumme

    rumme Member

    i didnt check its position when i assembled it last nite....whatever stock postion is.

    I did cut the baffel rod inside the muffler down so its 0nly 2" long now.... iM PLANNING ON drilling two 1/4" holes at the end of the muffler baffle tommorow and then lowering the needle clip 1 lower to see if it will make the engine run smoothly with the choke fully off ...
  6. Well let me know how you make out when you move it. I think that will solve your problem. Like I said too little fuel meens you have to close off air to balance the mixture so I'm pretty sure that will solve your problem......Just one more piece of advice I would get the bike running the way you want it BEFORE making any more modifications, that way you have a baseline as far as performance to start with.....Just my opinion.....
  7. adjusting needle should Do it. ( if no blockage in carb or fuel supply)

    I agree with MrRight.
    Mods should be done after Things are running smooth and up to par.

    As my shop teacher always said 25 years ago " KISS "
    Keep,,, It ,,,Simple ,,Stupid.. ( According to him Back then All of us in class where stupid).


  8. rumme

    rumme Member

    just tryed it....

    first thing I did was to make sure there wasnt any air leaks around intake/ carbereutor.....

    then I lowered the needle clip 1 increment....no change...I then lowered the needle clip to the lowest position down, 2 increments and the engine still runs best with the choke lever in the middle instead of all the way down.

    any other ideas to fix this problem ? Or is it allright to leave the choke lever in halfway position and just run the engine like that all the time ? Id rather get it so its working correctly though.

    Keep in mind this is a new engine and I havent ran a full tank of gas thru it yet....and I also took the baffle out of the muffler and cut the inside rod down to 2" then put it back together. Is it possible that I need to drill two extra holes in the back of the muffler baffle to remedy this problem ? Or maybe I need another jet ?
  9. Are you sure The carb is clean and not blocked .( Main jet isn't plugged)
    I would drop the bowl and give it a good look.
    Just a small piece of grit would cause the symptoms your describing.

  10. rumme

    rumme Member

    if the main jet was blocked, im assuming it wouldnt run at all....or having half choke wouldnt make the engine run good...would it ? In other words, setting the choke on half way makes the engine run decent.....how would that unclog the main jet ? If the jet was clogged, adjusting the choke wouldnt make the engine run better or make it act as though the jet was unclogged...would it ?
  11. rumme

    rumme Member

    and isnt there 2 pre-filters on these units...one on the gas tank petcok and one on the carbereoutor gas inlet ?
  12. Lets say the main jet is partially blocked, restricted, or manufactured wrong less gas needs less air therefore partial choke. What does your spark plug look like? Could also be low float level, not allowing enough fuel to be stored in bowl to supply engine. When you moved the clip, did it make any difference at all in starting or running? Did you have to change choke position when moving clip?
    Last edited: Jun 13, 2008
  13. rumme

    rumme Member

    the choke lever still needed to be in about the same position.....about 1/3rd of the way pulled up...

    will running it with the choke in this position hurt anyhting..or make it perform worse ?

    if I get a free hour of time. maybe ill take the whole carbereoturo apart...was hoping I didtn need to do that though, ecsepcially since its a new engine...

    should the float sit about even/ half way in the bowl ?
  14. rumme

    rumme Member

    one thing....the plug looks fairly good when I puul it out now....more of a grey/charcoal lok,,instead of balck...

    also, if I pull the choke lever all the way up, while the engine has warmed up and is running, it will immeaidaltley stall the engnine....so at least thatseems to be working correctly
  15. Its not a hard job, just do it on a clean uncluttered surface. When you got it apart clean it all with carb cleaner, blow the jet out. Running with the choke on I would think would hurt performance because your not getting FULL air and gas tht the carb should deliver to the engine, and if your wrong and you do have an air leak somewhere you are running the engine lean and at risk of seizing the engine. You need to pull the plug and look at it. When you bought the kit did you clean the tank out? You might check the screen in the petcock inside the tank, that is the only filter, there is none in the carb. I would also get an inline filter so you can see when you have fuel flow. What are you running for an oil/gas ratio.
  16. Well plug color sounds good and when you close choke and it stalls that is a good sign that there is no air leak. Possible the wrong jet was installed or it is blocked or made wrong. You could go to a hobbie shop and get a drill to be sure s/b around .026 #71 they are about $1.00. you could just push it thru the jet to clear it.
  17. If the jet was partially blocked it would run but you would need to cut down the air intake.

    If a motor only runs good on half choke after it has had time to warm up its a good sigh she's running too lean.
    its not getting enough Gas ,fuel the choke half closed will not Usualy unclog a jet but it limits the amount of air it can get Manipulating the correct air fuel mixture .

    If you have a compressor blow some air thru the jet.
    I know the Jet hole is Tiny but you could also Take a light and shine it on one end to look for little goodies.
    I use A small welding tip cleaner to make sure of no blockage on any jets im unsure of but I do not recommend doing this unless you now what your doing so you don't mess up the jets small hole.

    hope this helps.

  18. rumme

    rumme Member

    20 : 1 mix.....7 ozs to a gallon using MC1

    I didnt clean out the gas tank cause I didnt think it was neccessary and becuase my manual said there are 2 filters pre carbertour...one in the petcock and one in the inlet of the carb.......

    I guess ill take it apart.....:{ I think I may have some feeler gauges that are the round circular kind...and I could use that to go thru the jet....
  19. Mister right
    You beat me to it.:smile:
    I guess i type to slow LOL.

    well my lunch is over i'm going back to the shop.

  20. rumme

    rumme Member

    well since I know its not a air leak probelm..and adjusting the needle clip fully to the bottom position didnt fix it, then I will have to take it apart......

    I wonder if cutting the rod inside the exhaust down to 2" would be causing this ? Unfiortunately, I did that mod first.....before running the engine with the totally stock muffler.