2 smokers ; no power; slow speed

Discussion in '2 smokers' started by Stick_man, Jun 28, 2021.

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  1. Stick_man

    Stick_man Been here awhile

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    What could be causing this. 2 stroke is a HD aermacchi sx 175 ('75).

    Recently rebuilt gears (although it did it before). I have replaced air filter; have done numerous jetting combinations but ; i cannot go above 25 mph or go up hills.
    #1
  2. Mark G

    Mark G Been here awhile

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    Pull the exhaust pipe and look at the exhaust port. Has a wall of carbon built up so that the exhaust is effectively much smaller?
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  3. Stick_man

    Stick_man Been here awhile

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    how much are we talking ? I recently pulled it, and there was some that i cleaned with a scotch brite pad but, i would say it was like 1/16 in. smaller not even; just a thin film of carbon. what about the pipe itself ; is there a way clean that? Also can you clean air filter (paper)? It is new but maybe it was over oilled? or "new" is still 40 yr. old ; old stock ; how new is it?
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  4. Florida Lime

    Florida Lime Long timer Supporter

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    First time I've heard of a paper air filter being oiled. :dunno
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  5. Mark G

    Mark G Been here awhile

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    Carbon build up I was talking about would form a wall in the port, leaving a very small opening, so not that. Agree with Florida Lime, paper filters should not be oiled. If it is, get a new one. You could try a quick run with the exhaust baffle removed.
    Did this poem come on suddenly, or gradually?
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  6. Stick_man

    Stick_man Been here awhile

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    Then it is probably the filter. I really do not remember if it was gradual or sudden. It is been awhile since and I hardly rode it for years. What would be the point of running it with no pipe; you suspect something blocking the pipe? Sounds like the move is running it w/o the airbox
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  7. Mark G

    Mark G Been here awhile

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    I didn't suggest running it with no pipe, just with the baffle in the end of the pipe removed (and the pipe still installed). Carbon can build up in the pipe around the baffle and choke the pipe. But if the paper air filter is oiled, I'd start there.
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  8. Spikester300

    Spikester300 Roll Tide!

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    Build a small fire and lay the pipe in it and burn the pipe out. Don't get crazy with it just get it hot.
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  9. baloneyskin daddy

    baloneyskin daddy bikaholic Super Supporter

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    From my recollection of the HD dirtbikes, thats about as good as its gonna get. lol
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  10. Stick_man

    Stick_man Been here awhile

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    ok i ordered the air filter on ebay thank you all...and we'll see.

    PS - i already used my propane torch from home depot to burn all the oil from the baffle to the point the baffle turned white and had to repaint it. and i am pretty sure i removed it and started burning in the pipe a little too. it didn't change anything
    #10
  11. Stick_man

    Stick_man Been here awhile

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    New filter does not do the trick
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  12. Mark G

    Mark G Been here awhile

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    Then I would try briefly without the exhaust baffle (pipe on). Then I would put the baffle back in and try it without the filter. Are you sure the intake manifold is clear between airbox and the carb?
    #12
  13. Mark G

    Mark G Been here awhile

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    Back to basics - is the carburetor opening all the way? Does it have starter enrichment device? Is it stuck on? Did you pull the float bowl and see if it is all gunked up (technical term)? Is it battery ignition or magneto? Is it properly timed? May be getting time to do a leak down test on the bottom end.
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  14. snarlyjohn

    snarlyjohn Human money repellant

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    Have you checked for sufficient fuel flow?
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  15. Stick_man

    Stick_man Been here awhile

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    Yea not sure on the carb slide going all the way. I have to admit I never do the cable adjustment. But in any case it goes up and down and I have switched the needle settings several times. I may have to switch it back to the middle position - which it always ran the best back in the day. I have recently pulled the float so it should be clean there. It is a magneto and a relatively new old stock one. It has spark, and no idea on bottom end leak down. I put a new gasket in there when I rebuilt the transmission recently, and oil should not be going anywhere it should not be. Heck when I moved the needle down a groove , the plug was indicating a lean condition; as it should.

    Not sure what could get in the way of air box. It is only a little coupling rubber hose. i have had the magneot flywheel off so timing should have always been slightly different each time without a lick of difference. Fuel is an interesting question. I have pulled the screen in the tank and cleaned it. But I noticed when swapping in a new fuel hose; it did not like vinyl , clear hose from home depot or a autozone fuel filter (inlne) i.e. no gas would come out . I have since swapped in an auto parts store black fuel line, and it appears to do the job ok. I have tested it and gas comes out (into a container) not as much as it should maybe? perhaps petcock prob?
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  16. Mark G

    Mark G Been here awhile

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    Have you checked the timing, either statically with an ohmmeter, or dynamically with a timing light. If even a little mistyped, those old magnetism may provide a spark good enough to run, but nit run well.
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  17. Stick_man

    Stick_man Been here awhile

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    No I have not checked it per se, but I have had the flywheel ff many times 3x at least that I can think of and, I have to time it each time the flywheel comes off. So after timing it 3x minimum over the past year; it has not made a difference. I guess I'll check it again just to eliminate one more thing of the "basics".
    #17
  18. snarlyjohn

    snarlyjohn Human money repellant

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    Measure the amount of fuel flow over a minute. If possible, remove the plug from the float bowl (if it has one) and take the fuel from there rather than just out of the fuel hose. This way the entire system including the needle and seat is tested.
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  19. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Your checking the plug after dropping the needle shows that it isn't a fuel delivery problem. Poor fuel flow to the extent that the bike runs poorly means that it is too lean to run properly and it would be apparent by a very light colored plug, not your text book "chocolate brown". That lean would also mean additional heat and a reduced amount of oil which could cause it to cease.
    #19
  20. Stick_man

    Stick_man Been here awhile

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    If I remember the plug was brownish white in the middle groove needle position, and white lean in the bottom groove. Now in the top groove it should be fouled looking indicating rich. I cannot check the needle seat with the screw unscrewed; gas will come out the bottom and the float will not close. Carb is vhb27ad....[​IMG]
    #20