On your stock carb, clean it and replace the float needle and seat assembly to stop the overflow leak.  Parts still available from Yamaha or a good Mikuni dealer.

@ MarkT is the flywheel puller essential to getting the gasket out? Im on a pretty tight budget and was thinking of wraping a belt around then getting the bolt off for the magneto and mabye trying to use tweezers carefully to pull the gasket out and pvc pipe to reseat a new gasket but that might be a bad idea lol. I ordered the part you recommended, does it matter that my bike is a 125? im pretty sure they are the same design as the 175 at least for the crank. Hopefully this is the right fix. Do you have a specific website I should try for the float needle and the seating/gasket? Sorry for all the questions, I'm pretty new to all of this. 

Seal Mark is talking about is in behind the magneto so flywheel off & backing plate off with the coils. Gasket on the cover isn't important--well not from the running point of view. Propper puller is a "must" & is 27mm left hand thread & remove both washers behind the nut to get it threaded right home or can pull the fine threads. Back the puller center bolt right out so you don't get tricked by that bumping the shaft before right home. Here's a typical puller you need.

Left hand thread that is!! so left turn to screw it in. Puller center bolt is normal right turn. Meant to say you'll need a tool to hold the flywheel solid more to tighten it after so its good & tight or will shear off the crank key. Belt around might hold it to undo the nut. Here is a typical one below if you decide to go in there.

I'm not sure what "gasket" you're talking about... but no, you need the correct puller or you're likely to damage very expensive parts. Motion Pro is known quality, the no-name cheap ebay pullers can be of questionable quality.sometimes.    Do not try to use a jaw puller on the flywheel.   You will need a hand impact screwdriver or at least a good #3 JIS screwdriver to remove the stator.

Yes, seal is the same on the 125.  I like Rocky Mountain ATV/MC for parts.  www.rockymountainatvmc.com/oem-parts/Yamaha

 

@RT325 and @Mark T. I think I found a video of a guy replaing the seal I bought and im hoping if I follow what he did this will solve most of my problems (he did end up shearing the woodruff key) . So if im correct this (www.motosport.com/product/?cc=us&gclid=C...78-X001-Y007&variant[MOP0078]=MOP0078-X001-Y007) flywheel puller will help me get the parts off. I'll order something to hold the flywheel as well so I can try not to shear the woodruff key. Im also going to replace the needle valve on the OEM carburator. Is there anything I'm missing? thanks for all the help