Hello, I thought i could figure this out myself but it turns out I can't. I have a 1976 dt175 that has a clutch slip at around 4.5k full throttle. I already put bigger springs in it with little to no change. The clutch plates measured at 3.5mm and the metal ones at around 1.6mm. I have a ton of freeplay in the cable and still nothing.. I tried changing out the 10w 40 synthetic motorcycle oil with ATF and still, no change. its as if the bike shifts into neutral if i put alittle more than a hair of throttle on it.

Clutch sounds worn out.  Pretty sure 1976 should have 3mm friction discs.  So maybe you don't have a 1976?  Check your VIN.

Earlier models had 4mm friction discs.  (Same size otherwise.  It's also possible the 1976 still had 4mm...  but memory says it was the first year of 3mm.)

But if discs are 3.5mm they are definitely worn out 4mm discs.  Discs did not come in half sizes. 

the motor is from a 1975, i shouldve clarified that.. im getting 3.6 mm on the friction plate so im assuming that means i need new plates

Yes, make sure you get 4mm discs for 1975 or earlier. 

I don't remember spec but 4mm are considered worn out at something like 3.6 or 3.7mm...  you originally said 3.5...  which is absolutely worn out. 

As they wear, the friction plates form a rim on the outside were they mate up with the steel plates, so you need to measure them from the inside, not touching that rim. My '71 clutch was slipping badly, and the friction plates on it measure around 3.6 to 3.75 mm. When I got the new ones they were around 3.97 to 3.98 mm.

  

ok, ill order some plates and i really hope this will do it. the springs i put on were from a 76 dt175 which are slightly larger which i believe is an upgrade.

Define "larger".  Taller?  Thicker wire?

Springs are simple and complicated at the same time.  Thicker wire, smaller diameter coils and less coils per inch make for a stronger spring rate.  So a taller spring, while it might have more "preload" can actually be softer. 

One thing you can do if you have a drill press and a scale is measure the height of the boss the spring fits over with clutch assembled.  Then use the drill press to compress each spring to that same exact height and see which one is exerting the most force on the scale. 

In my opinion they slip because they get all glazed up & cooked from getting a hard time, 3rd gear motocross start etc--but maybe not, i see its a DT175. Once glazed & starting to get burnt from slipping it's all down hill for the plates. New plates always work well unless something else is wrong. Probably contradicting myself a bit so rewrote it lol.