I ride an 82 FXRS I picked up about 2 years ago. I've been using mobile 1 20-50 oil for about 8K miles. I see some experienced wrenchers say 50 or 60 weight only for shovels. What exactly wears out with using multi weight. So far the engine has been running fine. The valve train is a little noisy but the new Road Glide I rented in Hawaii had louder engine noises. I do have piston slap at start up on the forward cylinder but it goes away fast and was there when I got the bike.

 

The hydraulic lifters in the shovels where not very good and had sloppy machining tolerances and bleed oil as fast the pump could supply it they need the heavier weight oil to run somewhat decently . The bike will do fine with multi weight but bet she's making a lot of upper end noise and just feels a bit sluggish or there should be more umph there . If it seems to be working ok for you go for it what I will tell you do not use synthetic in her it will start leaking from everywhere in short order

 

I have always used straight 50 on shovels and everybody I know riding them use it.
As I pointed out in another topic, a mechanic specialized in old bikes suggested me using synthetic 20-60 to get rid of the valve noise on my '83 FXRT.
I have used it since march/april.
Noise is still there, but no leaks at ALL so far... just very high oil consumption, but no smoke from the pipes.
My next oil change will be straight 50

 

Your valve noise is more likely the rocker arms , 80 & up shovels had very loose end play tolerances compared to older ones . I've run across a number of bikes that had up to .050" slop from the factory and they make a lot of noise like that . Most mechanics overlook this for some reason and always go straight to the lifters as the problem .

Good move going back to 50 wt shovels do burn more oil with synthetics for some reason , all I can figure is something to do with venting timing pulling oil past the rings & more going out around the valve guides .

 

The oil topic has been kicked around for years, and there has been a lot of agreements, and disagreements.
As a rule of thumb for me, motors with a lot of miles (or unknown miles) probably needs a heavier single grade oil. These high milage engines are loose, and putting a synthetic oil in them will probably result in flattened crank bearings, due to the bearings not rolling with the crank, just gliding along on a thin film of oil. Synthetics will also seep past old gasket surfaces, and even break down old gaskets. On loose motors, synthetics will cause a lot of engine noise (piston slap, valve train noise, low end rattle).
That being said, if you have a known fresh motor, new crank bearings, cylinders, valves, cam bearings, and the oil pump has been checked to make sure there is no gouges in the walls, run the synthetics, or a multi-grade fossil oil. I did for years with zero negative results, and actually extended the life of the motor out past 70,000 miles. But you HAVE TO START with a fresh motor!
I had a 80" drag strip queen that had 250, 6000 rpm log book passes on it. That was three years of hard racing on the motor. When we broke the motor down to check it, there was zero wear and tear on it. We scuffed the cylinders, put new rings in it and put it back together and ran it another 3 years until I sold it. I was using Castrol Syntec at the time.
It's all up to you the owner as to what you want to do.

 

Thanks for the feedback. The bike only had 7500 original miles on it when I started using synthetic motorcycle 20-50. It uses about what the book says and it's not getting black. There are a few weeps but are not getting worse. It did sit for 20 years. When it's time to change the front chain sprocket I'll be replacing the inner primary seals anyway. I’ve never pulled one before so I'll probably post a question about it when I get there.
I've grown very fond of riding a shovelhead FXRS. It attracts attention from what it is instead of flash. My wife loves to ride on the back and that's a BIG plus and I can keep up with my friend on his late model BMW on highway 1 with her on the back which pisses him off a little. The front is raised 2" and the back an inch and a quarter with heavy duty shocks so we don't scrape.

 

Sounds like ur doing OK with it to me. But I've always used 50 or 60 in mine except for a while just before tearing it down for rebuild I was using 70 wt.

 

I'm certainly no expert, but I don't use synthetic in any of my old motors (bikes or cars). I ride quite late into the season (cold weather) and run a 20-50 non-synthetic motorcycle oil when it's under 50 degrees most days. Once it warms up in April or May, I go with straight 50. This fall has been warm so far so I'm still running 50. Going to be 70 degrees tomorrow. I have a '75 FLH.

 

I;m new to this shovelhead forum I run 76FXE which is stroked out to 84 cu. in. it has 57;000 miles on the lower end and still is really quiet freshened the top end up once. I;ve have been using 50 wt. SPECTRO oil in.