It should be ok. I was told by a Yamaha dealer to be sure to use a low detergent oil.

Yes, that's exactly what you need.  (wet clutch rated)

Disassembled the carb. Float gasket was in bad shape. It's in 2 pieces, with a small section pretty much gone. I have a gasket from the rebuild kit. It looks exact and is in much better shape. Do I just go with it? 

I tried posting a pic of the two, but I'm getting a weird error message "Could Not Move File into /Homepages/37/...etc."  Anyone ever get this?

Regarding the pilot jet...am I supposed to see a hole in it...because I don't. How do I ensure it's clean enough?

Yes, kit gaskets are fine, float valve should be too.  Just don't use "jetting" from the kit.  And yes, pilot jet should have tiny hole.  Soak in carb clean and if your friend can put jets in ultrasonic after they soak in carb cleaner that would be good. 

Be careful with the new floatbowl gasket. The floatbowl is brittle, as are most of the aluminum parts. If you tighten the screws too much it can crack where the screws are. I presoak a new gasket in gas and then install it and then tighten the screws slightly. After a few days I'll check them and tighten again if necessary or if gas is seeping past it. Be in the habit of turning the petcock to the off position when the engine is not running plus the rubber valve should be replaced. Yamaha still makes them.

Also I saw a previous post about Muriatic acid. I recommend against using that.

Si/oui/ja/ yes

What is the rubber valve you speak of (petcock). Was looking at the part schematics and I'm not seeing a valve.

Page 108 of the manual
Vintage Yamaha Enduro Fans - 74-76 DT100 DT125 DT175 A B C Service Manual (yamaha-enduros.com)

Another item we noticed regarding the oil tank. The oil gauge/sight glass (same link above, page 109) may have a slight leak. Anyone ever had to replace one of these? I assume it just pops out / unscrews? I haven't tried searching for the replacement part.

Item # 23 on the fuel tank page. Part # 214-24523-00-00

Item # 2 on the oil tank page. Part # 214-21761-00-00.

OOPS.
Disregard the previous post. I'm referring to the '68-'73 models.
You need the parts listing for your model.

www.partzilla.com/catalog/yamaha

Made some progress the past couple of days.

• Took apart and rebuilt the carb. Used the float gasket from the kit, but reused everything else after a run through the ultrasonic cleaner.
• Determined the air filter is shot...crumbled in my hands. Will search for a replacement.
• Installed the new battery.
• Removed the tank and currently is soaking with Evapo-rust

Something new...We noticed the ignition has some kind of gunk/debris in it (where key goes). The key will not slide in and I'm hesitant to force it. Any ideas on how to clean it out? Can WD40 be sprayed in there?