Looks nice ! Great bike for a youngster.

OIL
Complete oil and filter change. 20W50 API rated SF/SG engine, such as Valvoline VR1. Non-synthetic gear oil in the g/b, drive shaft, and final drive. Smell the drained engine oil for traces of gasoline.

CARBS
Drop the bowls and turn the fuel tank up-side-down to make sure there's no old fuel. Look at the bowl's interior. If you don't see muck you may not need to clean the jets. However you will need to pull the jets to replace the o-rings. Consult a parts diagram for their placement. You'll also need new rubber diaphragms and intake port hoses. And yes, a new air filter.

BATTERY
You'll need a new one. There are many good AGMs out there. I personally like the Odyssey PC680 ($109 Amazon), but it's half the size of your battery box and may present issues for you to secure. What ever you do, don't fall for the lawn mower battery. Also check both battery cables for corrosion under the jacket and condition of the terminals.

BEARINGS
You'll need to re-pack the head post bearings and both wheel bearings due to grease oxidation. You won't need any parts, simply wash out the old grease and install the new. You'll want a waterproof grease, such as boat trailer wheel bearing grease. A shot of grease in the swing arm wouldn't hurt.

TIRES
Not only have your tires probably dry rotted, but tire design and manufacture have changed drastically in the last 15 years. Your son deserves the safety of new tires (and tubes).

ELECTRICAL
There are sure to be many bad electrical connections. I like to unplug every single connector and apply a small dab of NO-OX-ID compound. The "must do" connections are relays, harness-to-harness connections, every connection on the multi-color board inside the headlamp, and both fuse ends. PS. Pack the tool kit with spare 8A German fuses which can be hard to find on the road.

LAMPS
You want your kid to be seen. You can add newer LED bulbs to the headlamp and tail lamp and not only be more visible on the road, but actually reduce your power consumption too. Be sure and match the color of the lens with the color of the bulb. E.g. Use red LED bulbs in the tail lamp. This is the link to the Cyron HL bulb I like.

SHOCKS
► Change the front fork oil with synthetic ~7W fork oil, such as Bel-Ray 7W.
► Change out the rear shocks. I prefer calling Hagon USA because they will set the shock up for the rider's weight.

FRONT BRAKES
Don't even think about riding the bike until the fluid and pads are changed.
► I hate amber DOT4 fluid, and vastly prefer purple DOT5 Silicone. Of course, you need to disassemble everything to install DOT5 Silicone, but thanks to the HIGHLY corrosive nature of DOT4 you will need to disassemble everything anyway !! (So why not ?!)
► The rubber brake hose should be replaced with Teflon (PTFE) lined "stainless steel" brake hoses. This will drastically increase the braking efficiency.
► Install some new EBC FA22 brake pads.

Ride it. You'll discover lots of little things in the first few hundred miles.

Great father/son project. Congrats !!

Many thanks. I forgot to mention I bought a new set of shocks about 15 years ago during my last ramp-up to restoration. They were korean something or other... supposed to be good for the money at the time anyway.
I'm sure there will be lots of ignorant questions from me in the future. Here are a couple:

1. What's the preferred place to buy carb rebuild kits, brake parts, fuses, oil filters, and other airhead bits?

2. Why non-synthetic oil?

3. Any ideas why the front brake lever comes to the bar? What could it be?

4. How do you wash old grease out of bearings? Gasoline? Diesel? Kerosene? Brake cleaner? Is the red high temp moly wheel bearing grease sufficient for re-packing?

I usually use a dealer for the carb stuff, good mail order outfit is A&S cycles, they offer free shipping. Your brake lever is going to the handlebar probably because the fluid has gone or leaked out. I would pull the master under the tank and open it up to inspect to see if you are lucky enough not to have pitting and just need a kit. also available from dealer, it would be a 14mm for a single disk unit. Your entire braking system should be checked out as water accumulates in the systems, so it should inspected including the calipers. I would replace the rubber hose portion of the system, Spieglers is a good source for stainless brake lines. there is a bike shop that sells them on e-bay, same items, free shipping.
cleaning bearings, brake cleaner, carb cleaner, gas, just flush it out, repack. As to using dino oil, I don't know, I use Motul in my airhead tranny and FD.

FRONT BRAKES
Don't even think about riding the bike until the fluid and pads are changed.
► The 2 rubber brake hoses should be replaced with Teflon (PTFE) lined "stainless steel" brake hoses. These will drastically increase the braking efficiency.
► Install some new EBC FA22 brake pads.

My bad. You have the brake m/c under the fuel tank and only a single hose as Jagarra correctly pointed out.

However, when the m/c is under the tank it usually leaks corrosive DOT4 all over the electrical systems parts which are located directly under the m/c. So not only will your frame need to be sanded and painted under the m/c, but also the electrical connectors and relays located under will all need to be washed with warm soapy water to get rid of the gelatinous brake fluid residue, which is still corrosive.

Many thanks. I forgot to mention I bought a new set of shocks about 15 years ago during my last ramp-up to restoration. They were Korean something or other... supposed to be good for the money at the time anyway.

Just so you know, the life expectancy of ordinary rear shocks is 5-8 years. Are yours rebuildable ?

1. What's the preferred place to buy carb rebuild kits, brake parts, fuses, oil filters, and other airhead bits?

► Try EUBMW for the carb kits and filters. EBC FA22 brake pads from Amazon. Fuses and oil from LAPS. All other parts from Bob's BMW or Max BMW.
► Brake m/c and caliper rebuild kits are expensive. Disassemble and inspect before purchasing repair parts. All my 1979 needed was disassembly and intense cleaning.

2. Why non-synthetic oil?

Some synthetic oils will leak past oil seals that are otherwise working quite nicely with mineral oils. It's a roll of the dice. An experiment could have unintended consequences, such as soaking the clutch plate or rear brake shoes. You could replace all the seals, but that is a VERY big and expensive job.

3. Any ideas why the front brake lever comes to the bar? What could it be?

Like I warned you, brake fluid has a very short useful life. DOT4 goes to heck after that and forms a crusty varnish and/or cake. Prepare to spend at least12 man-hours cleaning that mess of a front brake system up. By the time you finish I predict you and your son will both hate DOT4. 😆

4a. How do you wash old grease out of bearings? Gasoline? Diesel? Kerosene? Brake cleaner?

I wipe out the bulk with shop towels, then blow the caged bearings with compressed air, and finish using kerosene with a stiff bristle brush. It's fairly messy, but has to be done. Never use gasoline as a shop cleaner, unless your fire insurance is paid up and you have lots of doughnuts and coffee on hand for the firemen.

4b. Is the red high temp moly wheel bearing grease sufficient for re-packing?

Neither place sees extreme temperatures. But both these places see a lot of water. So the real question is this: is your grease water resistant ???

Hope this helps.

Thanks again. Yeah I never have used gasoline as a degreaser and wouldn't do it unless outside, with fire extinguisher, and wearing a fire suit. LOL

► Allow me to clarify....
When you re-pack the head post bearings, you don't fully disassemble the bike. Place a jack under the exhaust pipe or oil pan, remove the front wheel, take off the fork crown, and allow the forks to drop about 6" onto a support. This saves a lot of disassembly headaches. Here's a photo of how I did it on an RT...

Head Post Bearing Repacking

► Just my 2 cents.... While you have a lot of cost built into the items already listed. There are additional items and sensible choices which we could discuss that would give your son a chance at surviving his first year on public roads. The first of these is for you to read and discuss with him the findings of the Hurt Report. In view of the Hurt Report, another might be the removal of the "highway pegs" so that his feet are always in contact with the rear brake and gear shift pedals.

All the best.

Another good read is "Street Strategies" by David Hough.

Regarding the master cylinder, I would consider having the original sleeved and honed before installing a re-build kit. I had one done using a brass sleeve. Other shops use chrome plated sleeves. This will give you a more permanent repair that will not be subject to the trouble with corrosive brake fluid that attracts moisture. Last time I had a M C sleeved, the cost was around $100 that, when combined with the re-build kit, is less costly that a new M C, and in all likelihood, a permanent fix. My success with simply honing and installing a kit in one of those under the tank M C's is less than 50%. They always end up leaking at the plunger end.

I had mine resleeved after I put new seals in and discovered it wouldn't hold pressure. I used Apple Hydraulics to insert a brass sleeve in the M/C., great turn around time, cost about $100.00.

Thanks for the tips. I will probably have to re-sleeve the MC I guess?

Stupid question: is the number/model of the Bing carbs on a plate on the side? 64/32/11?

Correct. Pairs are numbered consecutively with the odd number first. My R75/5 has 64/32/9 &10. An R90/6 would carry 64/32/11&12. Now then, if you had a pair labeled 64/32/10&11, those would be mis-matched, with odd numbered carbs for one side and even numbered carbs the other, but not the pair originally employed on your bike. In a case like that, the bike would probably still run O.K.

Many thanks. I appreciate your patience with my dumb questions and I'm sure i'll have many more. 😀

Friend, the only "dumb" questions are the ones you don't ask !!

Friend, the only "dumb" questions are the ones you don't ask !!

Agreed. Please drop us a line every now and then to report on the progress.