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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    Update:

    We have been pulling the bike around trying to get it to fire up with no joy.

    I again removed the flywheel as on testing it looked like it was firing just after TDC.

    Maybe someone has tried to rig another flywheel as when stationary the spark occurs much too late.

    Does anyone recognise the advance system, I locked it with a screw, to full advance, replaced the flywheel, set the dwell and it briefly fired up.

    Now of course the case has a gut full of fuel and will not continue to run.

    Will let it sit open overnight and try again tomorrow.

    image.jpg image.jpg
     
  2. harley1-5

    harley1-5 Active Member

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    I knew a spark related issue was the culprit
     
  3. Awk08

    Awk08 Administrator Staff Member Technician

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    have you tried lubricating everything with WD-40, or maybe switching to a modern synthetic blend 2 stroke oil ?
    (I just had too)

    smiley-laughing021.gif
     
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  4. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Last resort will be WD40, and a match to light it, and this thing ain't running bean oil.

    Thanks Joe, now I know what the problem is, poor lubrication!:p:D:D.

    Certainly ain't spark related!

    image.jpg
     
  5. harley1-5

    harley1-5 Active Member

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    nice and blue
     
  6. speedyslyder

    speedyslyder 2 STROKES RULE Technician

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    i would say only option to bump up compression with topend rebuild would be to shaved the head..figure 8 lol or thinner head gasket..They were talking about these bikes on thumpertalko_O and they were saying 160psi as well or min of 130 who knows:)


     
    Last edited: Aug 29, 2014
  7. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Not going to spend any cash on it, got it as a quick fix to boost the coffers!

    Someone will give me $100 for it as it is!
     
  8. Bluesman

    Bluesman Member

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    Interesting timing advance mechanism. So, the points cam lobe is on a floating collar on the flywheel, that L shaped piece slings out when the flywheel spins faster, and rotates the collar clockwise as seen in the pic, which is counterclockwise when installed on the bike, breaking the points earlier. So, the slots in the flywheel must be so you can set the point gap. Out of curiousity, I thought, "hmmmm, I wonder if they made provisions to set the timing". I'm looking around and found this. It appears that the timing plate is slotted, although they don't show it. About 1/2 way down this page, they show a pic of the timing marks.

    http://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=28&t=3808&start=15
     
  9. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Boy, does this silly ol fart need his butt kicking for wasting folks time!

    Just thought I would re check the compression, must have been having an out of brain experience when I checked it last time.

    Just maybe all the kicking that I have been doing wore the rings out, or I read the gauge wrong!

    Why won't it start, you tell me!

    I just bet the pointer was near the 7, and I said ok 117psi.

    Time for a stiff drink if you ask me!

    image.jpg
     
    Last edited: Aug 29, 2014
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  10. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    In reply, the timing plate on mine is not slotted!
     
  11. speedyslyder

    speedyslyder 2 STROKES RULE Technician

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    well we got you think...hopefully you break even top end or no topend :)
     
  12. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    It is up the road as it is, I am not spending any more time on it.
     
  13. harley1-5

    harley1-5 Active Member

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    don't let it win
     
  14. 79 bronco

    79 bronco Moderator & Self Custom Psycho Staff Member

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    I don"t know???????
    It may be time to sell that bike, and get a new compression gauge! :confused:
     
  15. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Me thinks the bike is at fault, the $150 compression gauge is only 3 weeks old!
     
  16. harley1-5

    harley1-5 Active Member

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    rings are cheap lol
     
  17. 79 bronco

    79 bronco Moderator & Self Custom Psycho Staff Member

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    OUCH!
     
  18. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Nothing is cheap here, especially good quality toole!
     
  19. blasterdemon7

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

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    Dont worry about it. Even the best of us do sh*t like that sometimes. I'm sure even the great Ken O'CONNER has done it a time or two.
     
  20. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Thanks, I suppose what I know today has a lot to do with the mistakes I made in the past!

    I should have realised that when I was kicking the engine turned over easily!

    I am still trying to fathom out where I got a reading of 117psi fixed in my brain.

    I realised that low compression would make for difficult starting, but I carried on rewardless..

    There may be hope yet, I could have a cylinder and piston laying around in the junk pile.
     

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