1977 Yamaha Dt175 help!

Discussion in 'Yamaha' started by Blaaster, Aug 29, 2014.

  1. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    image.jpg Compression 117psi
    Reeds checked OK.
    Carb cleaned and float level set.
    Jets and passageways purged with compressed air.
    Leak test passed.
    Flywheel lapped and fitted with new Woodruff key.
    Points cleaned.
    Automatic advance repaired.
    Great Spark at the correct time.
    New B8ES spark plug.
    Another new spark plug.
    Exhaust port free of carbon buildup.
    Plug shows signs of fuel reaching the combustion chamber as it gets damp and smells of fuel.
    Everything seems to be working just fine.

    Have I missed something?

    Am I getting to old for this it will not start, not even with a tow.
     
  2. harley1-5

    harley1-5 Active Member

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    new plug?is coil possibly weak,sparking when at rest and not under pressure ?
     
  3. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    It is a very healthy bright blue spark, could it be possible that I have got 2 bad brand new plugs.

    Just let me tell, I am getting very close to pouring some fuel in the plug hole or giving it a quick squirt of starting fluid.

    Thinking again, that will solve nothing, so will not do it!
     
  4. harley1-5

    harley1-5 Active Member

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    if fuel is reaching plug sounds to me like spark issue[could be wrong]
     
  5. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Fuel is definitely getting into the combustion chamber as the plug if getting wetted by fuel.

    I will get a new plug tomorrow to see if that fixed the problem.

    I have checked the timing and the points are opening about 15 deg BTDC.

    I very seldom get stumped but this one is leading me a merry dance, it has got to be something simple as I have explored just about all avenues.
     
  6. Awk08

    Awk08 Administrator Staff Member Technician

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    exhaust clogged
    pull pipe from head and give her a few kicks w/ new plug
     
  7. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    I have had the header off, no obstruction found.
     
  8. blasterdemon7

    blasterdemon7 I'm not mad. I'm winning.

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    If there easy and cheap to get, I would replace the reeds just to see. Had the same problem on my Blaster. The reeds looked fine but I replaced them anyways and it ran.
     
  9. Awk08

    Awk08 Administrator Staff Member Technician

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    you tried to start it with the header off ?
    how did you verify no obstruction ?
    could be in the silencer.

    it looks like it's been sitting for a while ?
    in a mouse infested shed ?
     
  10. bansheedave

    bansheedave Active Member

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    Think it may need a battery in the system to properly run?
     
  11. bansheedave

    bansheedave Active Member

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    If you are getting spark and the plug is wet but won't start, I just read you maybe getting to much fuel. You float maybe sticking on you.
     
  12. snowrider

    snowrider Member

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    try pop starting it while some pulls you or down a hill
     
  13. MercMenace

    MercMenace Mountain Man

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    Compression on that should be around 135 on the low end iirc. I had a 78 that hit 160psi.
     
  14. MercMenace

    MercMenace Mountain Man

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    Pour a litte oil in the jug and compression test again.
     
  15. speedyslyder

    speedyslyder 2 STROKES RULE Technician

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  16. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Thanks for the replies.

    The bike was running just prior to coming here, the problem that was reported to me was no spark.

    I took the flywheel off to find the woodruff key was sheared, I fixed the advance bob weight which was somewhat sticky, and filed the points.

    The spark is strong enough to knock a male dog off its mate.

    I have had the baffle out of the silencer, it was a little mucky, but no rodent nest.

    Today the pipe will come off again, I will get the compression up some with a drop of oil.

    I will take the reeds off again, just in case I overlooked something, I am pretty confident that the float is free and doing its job.

    My Lad has had his fingers it it as well, trying to help, maybe we have been undoing each other's fixes.

    I do not have a manual, thanks Speedy, it may shed some light on the matter, this may be a bike that gets parted out!

    As you see, I have very little hair, and more is being torn out every time I think about the bike.

    I very seldom have to ask for help, I can usually come to grips with most problems, but this thing is becoming a pain!

    I will get back in a few hours with more findings, thanks again.
     
  17. MercMenace

    MercMenace Mountain Man

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    As soon as you ride it you'll want to keep it. They are fun bikes.
     
  18. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    I bought it as a simple fix, no spark, no rocket science here, magneto, points, coil no worries.

    Proved me wrong!

    The last bike that threw me was a DT175, so I know how much fun they can be.
     
  19. harley1-5

    harley1-5 Active Member

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    you will figure it out
     
  20. snowrider

    snowrider Member

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    if the bike is mobile I think you should try pop starting it couldn't hurt. I had a 2008 yfz 450 (completely different animal,I know) that simply would not start , even with some starting fluid. I had my dad pull me down the road in 3rd gear and it fired up and started great after that
     

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