Petcocks can be pesky. If fuel runs good when it's in the prime position, get a inline fuel filter and on/off valve (I get mine from advance auto in the lawn mower section). Put the valve close to the carb as posible.

The carbs..fuel has been leaking by the float needle alot these days (I think ethanol) It seems that when shutting off for the day, if you shut the valve off and run it for a minute it eliminates a ton of aggrivation from flooding.

Clutchs: you'll need to get in there and service both front and rear.
Front: make sure the rollers don't have any flat spots, the roller tracts are not badly grooved, and the roller plate key notch is fine. In stock foorm they are packed with grease and that usually gets hard, limits roller travel, and ruins the parts mentioned. FYI Only a dab of grease is needed to hold the roller in place durring installation.
Rear: stick your finger in the bearings and turn. These bearings wear out. Lightly sand the glaze off the contact pads.
To make clutch maint easy, cut the footpegs in 1/2. Then make a piece to stick in the end to rejoin them. This way you can remove the left footpeg and get it out of the way. This saves alot of time and grief. I lathe a piece of aluminum but I've seen many versions.
FYI: other than a belt, there are NO aftermarket clutch parts. All Suzuki.

Motor pivot bushings: The bolt/nut needs to be really tight. This fixxes most side to side movement. If they are bad, I use a heat gun and they come out/in easily. I use a c-clamp and a cpl sockets.

Cases crack in front of the front sprocket and where the rear end bolts to the cases. Make sure those bolts are tight.
Frames can crack on the bottom where the 3 tubes come together and also on the down tubes (carb area).

Thumb throttle gets loose. It's where the thumb throttle goes thru the mounting part. The hole wears.

Rear brakes last forever but the brake arm will need to be moved on the splines to adjust at some point.
Front brakes: the pin that goes thru the backing plate usually neeeds lubed.

Mods to just get it running a lil better:: shave the head .030, remove 2 front clutch rollers, and cut the rear clutch shoes down to 180 grams.
That's about it.
Have fun.