2stroke headache- help needed in diagnosing my DT 175 MX

Discussion in '2 smokers' started by jank, Mar 24, 2015.

  1. Gamequeazy

    Gamequeazy Curbjumper

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    Ah, you're right I was mixed up. Sounds like the main is clogged or the needle fell off the slide or something similarly whacky.

    I had similar symptoms on my old XT600, the PO had used RTV to hold the fuel pickup on the petcock on... You know the rest of the story lol!
    #21
  2. jank

    jank Been here awhile

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    WOW, putting silicone near the fuel system is something i won't be doing any time soon again. It turned into jelly, expanded, and clogged everything.

    After taking the carb apart, and cleaning it the bike runs on the whole rev range, but there is still something wrong.

    When the engine is cold, and I try to use the choke, I flood the engine. Even cold engine starts without choke.

    The engine idles nicely, and runs smoothly over 4000RPMs but below that it's a bit choppy, and uneven.

    The float level is 21mm (checked both by the caliper, and the overflow tube), the jet needle in on the middle notch, and the air screw for the jet pilot is 2,5 revs out (as in the manual).

    Any suggestions?
    #22
  3. Winnipegfats

    Winnipegfats Adventurer

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    I have a similar issue with my 175. My routine to start the bike cold is to open the fuel tap, let it sit for 40s-1m, kick it a couple times, close the fuel tap, open the throttle and kick until it starts, open the tap, and let it warm up.

    I'm sure I could tear into it and try to fix it, but I chalk it up to the bike's "personality", rather than risk making matters worse by meddling.

    For me the big issue is that if I leave the tap open when not riding, the engine will flood so bad it hydrolocks, and I have to remove the exhaust and tip the bike up to drain the gas out of it, then kick for half an hour with the kill switch on to push oil back into the engine before running it. I suspect a leaky float.

    Back to the issue of a rough ride below 4k; I had the same thing when I first got the bike started. If I wasn't hammering the throttle then I'd ride so rough I'd likely idle down and stall. I messed with float levels and jetting and carb cleaning for like a month when a buddy finally said "did you check your fuel filter?"

    The tap was clogged.
    #23
  4. Gamequeazy

    Gamequeazy Curbjumper

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    I'd say mess with the air screw some, see if it helps? 2 strokes are a bit picker about ambient temp and such
    #24
  5. jank

    jank Been here awhile

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    Winnipegfats- i would go crazy with a bike acting up like this, I guess I'm th mettling type ;) The tap is clean by the way.

    Gamequeazy- I will adjust the pilot jet air screw, according to a link I found, but I doubt that this is the reason. Before the carb did not flood the engine with gas, and now it does. Guess I will take the carb off again, and blow it again with solvent and compressed air.

    Aby more suggestions? I would like to dial the DT in as I have a SR500 waiting in line to be taken care of :)
    #25
  6. Gamequeazy

    Gamequeazy Curbjumper

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    If the bike is starting cold with no choke.... that feels like it is jetting pretty fat down low, right? I want to say float height too but you said it's good. The floats don't have any pinholes in them do they?
    #26
  7. jank

    jank Been here awhile

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    Thats what I was thiking- choke enrichens the mix (more fuel), so it seems that if it starts cold with no choke, it is too rich.
    Before I started to "mettle" with it, it started cold with choke on, and did not flood the engine.

    Maybe while cleaning the carb i damaged the float? I'll take the carb off oce again, clean it, and check the float level for a longer period of time through the overflow tube. Maybe it's not sealed as you say, and sinks slowly?
    #27
  8. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    You have described the classic symptoms of a plugged pilot jet.
    #28
  9. Gamequeazy

    Gamequeazy Curbjumper

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    You could probably take the float out and shake it and listen for sloshing. Or stick it in some water and see if it floats evenly. My XS400 drove me up the freakin' wall, wouldn't run on one cylinder.... Pinhole in the float was causing of the flooding of the engine.
    #29
  10. GP MX Fan

    GP MX Fan Been here awhile

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    I am a big believer in completely rebuilding old carbs with as many new OEM parts as possible. it's darn near impossible to get gunked up old jets as clean as they should be, and quality suffers in many of the aftermarket suppliers.
    #30
  11. mikeyvet

    mikeyvet n00b

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    That oil looks like a blown crank seal, they sometimes blow out on the gearbox side where the retainer doesn't go all the way around. But they tend to run not so bad but blow a heap of white smoke.

    Did you pull ALL the jets out of the carb, a blocked emulsion tube can do this.
    #31