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Joined: May 03, 2010 Posts: 2 Location: Somerville, TN
Posted: Mon May 03, 2010 6:07 pm Post subject: '79 dt 125 help
hi all, newbie here, got some questions about this bike. its really got me stumped.
well, like i said, its a 1979 dt 125, 2-stroke and air cooled. i think its flooding really bad. it will start and run, but it will only idle very roughly. it will not rev at all, even when the throttle is turned. after it has run for a minute or so, it will die and not start back for a day or so. when i looked at the spark plug after i had it running, it was black and dripping with gas (i had just put this plug in the engine brand new out of the box). the carb has been cleaned well several times. i have checked:
to make sure the float is floating
that the needle valve and seat can seal and is not pitted
the cylinder wall is not scored and it has compression
the throttle works smoothly
there are no air leaks that i can find
the reed valve looks to be in good shape (no cracks or breaks anywhere)
i have been around and around with this bike for about a month now. i cant figure it out! anyone got any suggestions for me? i would sure appreciate it! Thanks,
Andy
I'm running a 1975 DT250 with almost the *exact* same issue.
My big difference is that the bike behaves pretty normally when the choke is on. With the choke off, I get the same problem. Erratic idle and eventual stall, and if I touch the throttle it dies instantly.
Strangely enough, it runs very well with the choke on - the throttle doesn't kill the bike, it revs cleanly, sounds good...
I'm pretty inexperienced with carburetors. I've followed the teardown/rebuild instructions in the manual several times with no results. What should I look for? (and probably with a hand-holding on how to do it, I'm really new to carbs).
Joined: Oct 30, 2009 Posts: 612 Location: Parker, CO
Posted: Fri Jul 16, 2010 5:19 pm Post subject:
Author Message
mightysox
Your problem is most likely a plugged pilot jet. Remove it and hold it up to light, if you can't see through it, it's plugged. You should see a very tiny round hole through it. I need good reading glasses to see it. Either replace it from a kit or use a fine soft wire from a jet cleaning tool to push through it. It's probably about a #28. Sometimes a single strand of copper wire from a 18 gauge stranded wire fits just right. Soaking carb cleaner doesn't always clean this jet out.
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