Hi folks! Just found this community, hoping to get some expert guidance on my goal of getting an old 1978 DT175 running right. Backstory: I bought this bike over the summer, and it ran well enough for me to at least ride it and make sure it shifts, brakes, etc. I've slowly been working on getting it to a decent condition, but I'm having a hard time with the engine. It's a strange enough problem that I haven't found a forum post that exactly matches my issue, and I'm not experienced enough with 2-stroke engines to know exactly what to search for. I haven't really ridden it at all since I'm worried about damaging it further.


Description of problem: Bike can be started alright, takes a couple kicks, and idles alright (haven't fully dialed in idle since I'm having bigger issues). It runs, but very poorly: power is a little jerky, and sluggish at low RPM, but feels like full power with a good throttle pull. Coming to a stop, it stalls every time, then takes a few kicks to start again. Bike runs worse off choke, but also is fairly smoky (though nothing horrendous). Sounds terrible to me, but I'm not 100% sure how much is standard 2-stroke noises vs. my specific issues. I have a short video of a 50 yard ride here if it's helpful.

What I've done so far: cleaned the carb (twice), taking care to clean all the jets. I'm fairly confident I did this right (not my first gummed up carb). Float isn't quite right (slight fuel drip out of float bowl overfloat), but I don't think it's related.
Cleaned the tank and serviced the petcock, so fuel delivery shouldn't be an issue. Fresh gas too.
Checked that the autoluber was working.
Replaced the spark plug (gapped to spec), and checked spark.
Cursory compression test (thumb on spark plug hole) - haven't properly tested compression though.

Things I'm wondering about:
Timing issue or intermittent CDI failure? lack of primary compression? Something with the reed valve? Leaky head gasket? Fuel mixture problem?

I'm just not very familiar with 2-strokes, any guidance would be very much appreciated! Can take a video and post it if that would help

HI Alfonzo

im having a similar issue with my dt175.  What was the outcome for you ?

Phil

Sounds to me like your high float level IS an issue, when you come to a stop the high fuel level goes forward into the throat of the carb and floods the bike.  I'll bet if you pull the plug before trying to restart it'll be good and wet.  Just my no nothing opinion

I'll guess exhaust restricted with carbon although doesn't really sound that way by your description. But Exhaust is super important on two strokes. Carbon grows in any small holes or in the built in spark arrestor in the tail muffler. Could go give it heaps without the tail muffler. Remove it totally if you can stand the noise.
Yes a video would be really good please. Not easy to do a good one but!! longer the better within reason.

Sorry found the video. Sounds over rich & blubbery but would be good to hear it wound right out up through the gears on the road because if it revs right out & has good top end then won't be exhaust. But there's not a lot that can make it go all rich at low revs. Only things like idle mixture screw turned right in. Or slide needle sitting on top of the plate instead of retained under it by the clip. Main jet fallen out. Idle mixture jet fallen out. Choke left on instead off off--actualy sounds more like that.If its a pull button choke the running should be pushed in. If its a lever then flick the lever up. Check that & anything stuck in the air filter air intake like a rag left somewhere around there. Check choke!!