Hey guys, new here. I recently I have been working on my 1974 DT125, I replaced the throttle cable and cleaned the carb. However, the bike is running quite odd. It runs okay under 4-5,000rpm but as soon as your rev the engine any higher is suppters and eventually will die. But it will rev out to red line when in netural. I'm not sure if this is a carb issue. I will add, the battery I am running is not very strong and has sat for awhile. Thanks for your input

The fact that it revs out with no load isn't particularly relevant .
You didn't mention whether it had been running right before you worked on it ,
or if you've only just got it running , so have no prior running history for it .

So, last year the bike was running normal. However, it would occasionally have this issue. But it would resolve itself. I just assumed it was a carb issue, so I clean it with carb cleaner and blew out with compressed air. Hoping this would fix it. I have noticed oil leaking from exhaust which I know is not normal. So my next thought would be to burn out the pipe?

Thanks for the reply btw

There's an oring in the carb that seals the main nozzle to the float bowl... if it goes bad, bike will run rich.

First thing I'd do is the battery though... that model needs a good battery to run right and at high rpm it might not be up to the task... charging system could need attention too... great troubleshooting in the manuals in the tech library.

I’ve got 1600 miles on my totally “new” top to bottom motor. I have had a little bit of oil drip at pipe/silencer junction. Could be a pipe deal or something else. This sounds like a good time for a video. I’d bet the gurus will want one. If possible, take one, post to YouTube, and link it here. If you’ve never done it, it’s not as bad as it sounds and is a very helpful thing for diagnosis. Good luck.

I was wondering about that o-ring.... I will take a video tomorrow and post it. Thanks guys for the response much appreciated

Similar question, does anyone know factory carb settings 1975 DT 125B? I think the air screw is 1.5 turns out, but unclear on idle screw.

There is no factory setting in turns... it's a stop screw that holds the slide from closing all the way. You turn it to set the idle speed to the correct idle rpm.

Shoot for 1300-1400 rpm per book.

Hey guys, hope this thread isnt dead yet lol. Sorry I was just able to get a battery installed today. Still no video though, I will try to get one tommorow. Just wondering if anyone knows where to source the o-ring for the main jet or if just a normal o-ring with the correct ID will work?

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