DT125 - troubleshoot - starts then dies.
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DT125 - troubleshoot - starts then dies.

This is a discussion on DT125 - troubleshoot - starts then dies. within the Technical forums, part of the Caferacer.net Forums category; picked up a dt125 at mid-o last month and finally got home this week from road trip and started messing w it. it ran when ...

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Thread: DT125 - troubleshoot - starts then dies.

  1. #1
    Senior Member bfont52's Avatar
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    DT125 - troubleshoot - starts then dies.

    picked up a dt125 at mid-o last month and finally got home this week from road trip and started messing w it. it ran when i bought it but not well...idled ok. sometimes would ride. sometimes would die after switching into first and getting 30-40 ft down the road.

    messed w/ it this weekend.

    cleaned carb real good...no new gaskets though.
    de-rusted tank.
    cleaned petcock.
    fresh gas(pre-mix w/ amsoil saber 50:1 - oil injection is disabled.)

    bike had a uni pod filter installed on it. i could not get it to start. eventually took off the filter and put my hand over the back of the carb intake and the thing starts up after a few kicks like this but won't idle. dies shortly after. i have the airbox so i'm planning to put that back on.

    I'm having issue w/ the float as well...if i set it to factory height the bowl overflows out the leftside...so i had to set it at a pretty extreme height to keep it from overflowing...i check the needle w/ the bowl off the carb and it's not sticking so good there.

    thoughts on issues? wondering if maybe there's an air leak but the rubber manifold looks fine, still soft. not hard or cracked.

  2. #2
    Senior Member crazypj's Avatar
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    Doesn't the oil pump line connect to spigot on carb?
    Check reed valves are sealing
    Could also be air leaks on main bearing seal behind generator rotor, base gasket leaks, hell almost anything on an old 'stroker' with unknown history
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  3. #3
    Senior Member bfont52's Avatar
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    hey,

    yea the oil pump line does connect to the spigot on the carb. he had that line connected to the same carb spigot while the end that was connected to the oil pump was curled around connected to the spigot on the other side of the carb that's supposed to have a cap on it according to parts diagram.

    i opened up the oil pump cover...the oil seal on the worm shaft for the pump is seeping oil when i jiggle the worm gear in and out so at the least i guess i need to replace that. guessing it's possible the crankshaft seal is leaking too on that side maybe? if i want to just use premix do i need to pull that worm gear and just plug that hole? seems if i don't there would always be a leak through the oil pathway no?

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    Senior Member 44dwarf's Avatar
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    Other side of the worm gear is a plastic gear bolted to the worm shaft just take off the gear. or better yet fix the autolube Yamaha got there's right it works well and make refueling easier. Sounds like you need a "Tune Up kit" points, condenser and spark plug. Then start looking at jetting cause your likely way lean on fuel if its not been jetted for the pre-mix. Yes crank seal may be a problem too if its sat a long time they tend to get hard and leak
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  6. #5
    Senior Member bfont52's Avatar
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    Quote Originally Posted by 44dwarf View Post
    Other side of the worm gear is a plastic gear bolted to the worm shaft just take off the gear. or better yet fix the autolube Yamaha got there's right it works well and make refueling easier. Sounds like you need a "Tune Up kit" points, condenser and spark plug. Then start looking at jetting cause your likely way lean on fuel if its not been jetted for the pre-mix. Yes crank seal may be a problem too if its sat a long time they tend to get hard and leak

    cool. thanks for the info. can't i just up the oil level in the premix to compensate? would like to see if can get it started before replacing too much shit. think the PO pulled the oil pump b/c it wasn't working...

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    Administrator WERA689's Avatar
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    That would take you in exactly the OPPOSITE direction from where you want to go. Any liquid that isn't fuel leans the mixture overall. This is a VERY common misconception you're laboring under. IOW, adding more oil will LEAN your mixture more, not richen it.
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    Senior Member bfont52's Avatar
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    Quote Originally Posted by WERA689 View Post
    That would take you in exactly the OPPOSITE direction from where you want to go. Any liquid that isn't fuel leans the mixture overall. This is a VERY common misconception you're laboring under. IOW, adding more oil will LEAN your mixture more, not richen it.

    gotcha. was wondering if i had that backwards. well i got the thing started. didn't really change anything. just tinkered w/ shit. took exhaust off and retightened(there's no gasket btw). took reed valves off. they look brand new. retightened. then kicked a few times and started.. wouldn't idle at first then idled ok after she warmed up. rode around for a good 20 minutes or so...needs a lot of revs to go anywhere in first...like almost redline. turned it off for a bit then tried to ride again and it stalls out in first unless you gas the hell out of it(which is what it was doing the day i bought it). also backfiring a little bit. popopopopopop unless you get the revs up.

    gonna order an exhaust gasket.....you think the rest is mixture being too lean?

  9. #8
    Senior Member 8ball's Avatar
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    When you cleaned the carbs, did you clean out the emulsion tube holes on the pilot jet? ....as well the passage the pilot jet fits into? (I don't want to assume too much)

  10. #9
    Senior Member bfont52's Avatar
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    Quote Originally Posted by 8ball View Post
    When you cleaned the carbs, did you clean out the emulsion tube holes on the pilot jet? ....as well the passage the pilot jet fits into? (I don't want to assume too much)
    yeah, i poked through all the jets and everything w/ a needle and flushed all the holes w/ carb cleaner before and after. though i forgot to do the passages in the carb body.

  11. #10
    Senior Member 8ball's Avatar
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    I had one of the starter circuit (choke circuit) passages plugged up on my GS550 and it drove me nuts for a few weeks. One cylinder wouldn't fire until the bike warmed up enough to be off the choke. When I finally figured it out, it was like being hit with a "stupid brick"! I had cleaned out EVERY other passage in those carbs, but missed that one!
    WERA689 likes this.

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