Now that I’ve gone thru most of the electrical and mechanical items I’m trying to get my 175 running great. The previous owner was running a pre- mix fuel when I bought and since I’ve had it it seems the auto-lube system is working fine. When I take the bike out and get to high RPM’s it seems to be “ missing” or revving like it’s not smooth. If I back off the throttle a bit it clears up and runs good. Could this issue be because it’s getting too much oil in the fuel mixture. I haven’t run it with straight gas in the tank yet as I wanted to make sure the auto-lube pump was working first. Any ideas???

First off, welcome.
Second, a little more information might help. What’s the needle set at clip-wise, main jet size, premix ratio? Have you tested the output of your pump at low and high revs? Have you done a leak down and vacuum test? What seals and gaskets have been changed? Has the carb been cleaned multiple times and a few more? Has the emulsion tube o-ring been changed? This can cause odd symptoms. It sounds to me like a rich condition at high idle but I still doubt myself enough that it could be a lean condition too. I guess I’m wanting to know more about the overall condition of your motor, so we can rule out things and narrow it down. I’m sure we can help, especially the guys that have been doing it forever. We have some that will impress you! They’ll be along eventually

What year 175 is yours as could have the dreaded Oring problem but only if its old enough to have the main jet in the side fitting in the bowl. Does sound like its too rich on the main jet though if it goes better when you roll the throttle back a bit. Video is best otherwise it's all guess work. Airfilter ok & not restricted. exhaust restriction can cause very much the same top end symptoms--actually i'll guess exhaust problem first i think.

First, thank you for the replies. I have only had the bike in hand for a little less than two weeks so I still have a lot to do. As far as the carb, or anything else beside some electrical and sprocket changes, I haven’t done anything. It’s a 1974 DT 175A model. The pre mix is at a 50:1 ratio. I haven’t checked the output of the pump with the engine running but I did do a test by rotating the wheel of the pump with both the throttle open and closed and it seemed to be close to the specs in the manual, but I know my test was not exact. Should I do a test with the engine running? It doesn’t appear like any seals and gaskets have been changed, but not sure on that. The air filter appears new and air box is clean. I’m not familiar with the emulsion tube O-ring.
Could a condenser going bad cause this. Points? Should I get a carb rebuild kit? How do I test for an exhaust problem? I’ll try to post a video.
Thanks for the help!
I did pull and change the the plug and the old plug looked pretty good. The electrode was a medium brown color.

Go to the tech section and download the manual if you don't have one.It's free.
Secondly bleed the two stroke oil pump if you haven't done that either or air will prevent oil from getting fed into the fuel system.
The manual will give you pump settings and how to measure them.
Regards Ted

Ok guys. I changed the 46 year old tires so now I’m not so afraid to take it out and open it up. It consistently starts missing or running poorly at about 4500 rpms in every gear. It’s almost like it’s got a rev limiter on it, ha ha. Anyone experience this before? Where to start?

Important to know the answer to whether the miss is more RPM related or throttle opening related...

So many people report a problem at an "RPM" when what they are doing is opening the throttle all the way... just like you said the problem gets better when you close the throttle some.

Engine should rev up cleanly to redline with very little throttle (with no load for sure) and also in first gear on the flat or downhill. Does it?

If it revs cleanly to high RPM at some throttle positions but not others, then it's likely to be jetting. If it won't ever go over 4500 rpm, then I'd start with electrical.

Always make sure the basics are covered... clean and properly oiled air filter... exhaust not plugged up with years of old carbon and crud.... good spark plug... timing set to spec or close... etc.

Front brake shoes? Then and only then would I be unafraid to take it out and open it up.

Mark, after reading your reply I went out to re-check. It does red-line fairly easy sitting still and got the engine to rev good in first gear. The faster I went and in the higher gears, 4th and 5th, is when the roughness really appears. Can’t get it past about 45mph and 4500 rpms. Also, not positive yet, but it seems to get a little worse when it warms up good. I’ll let it cool and try again later.
How do you clean the exhaust and remove the carbon build up? I’m not sure it’s clogged, but I could clean anyway.

Put tape on the throttle tube and housing and mark 1/4, 1/2, 3/4 throttle opening. Use it to tell how far the throttle is open and if rough running is related to throttle opening... better/worse at different openings?

Burning out the muffler with a torch or in a fire works good. You can try to temporarily run with no muffler to see if it stops the problem.

O-ring on emulsion tube in carb can also be a problem as already mentioned... definitely worth checking as it's a common problem. And yes, if running rich it would get slightly worse when hot.