Your rear sprocket is worn out, too. You'll see when you get a new one and compare the valleys, which are wider than they should be. This sprocket will quickly wear a new chain's pins and side plates so it "fits" the old sprocket.
The O ring 530 chains are too wide for the 550, due to the added width of the o rings. They will bite into the seal rubber as the pictures show above. That seal is metal backed behind the rubber, but the metal is very thin. Once it wears through that, the seal is toast oil spews, and it requires splitting the cases to replace it (*IF* you can find a new seal). I feel Fritz is foolish using the 530 oring chain without modifications until a more serious failure shows up. (IMO, no offense intended.)
The front 530 sprocket can be milled to allow an offset washer to be used on the shaft, which moves the front sprocket outward to gain the required clearance. The clearance becomes less as both the chain link sides and the sprocket tooth width wear to allows more lateral movement of the chain on the highway. Alternately, you can use a 520 oring chain with the corresponding sprockets, as you are replacing them anyway.
I do NOT recommend going up on the front tooth count for the 550. An even-firing inline-four engine is in primary balance because the pistons are moving in pairs, and one pair of pistons is always moving up at the same time as the other pair is moving down. You will not get the buzzy vibration like the twins do.
It is a high RPM engine, quite unlike the twins which have good torque, the 550 does not have good low or mid range torque. You need the RPM to make the bike scoot. Dropping one, two or even three gears to get the bike to scoot is routine. I had a 650 BSA which you only needed to do throttle twist to pass. On the 550 at 40 MPH you'll drop to second gear to pass. (And it will pass quickly) Raise the sprocket ratio and you are lugging the engine, or dropping to lower gears to get any throttle snap. Raising the ratio also taxes the clutch more. At any rate, be prepared for a lot of gear changes on the 550. It will become second nature after a while. If you use throttle as an escape maneuver in traffic situations, you be happiest at about 3500-4000 RPM. The only sprocket change I recommend is dropping a tooth in front, ONLY if you are only driving around the city streets and very seldom are on the highway.
Anyway don't be afraid of the RPM on the 550. It was built to take it with aplomb. Anything under 9300 is fair game, and I do believe the engine likes it. You will HATE the bike if you try to keep it at the same RPMs as a Bonneville twin. The styling may be similar. But, they have very different hearts in them, along with engine management ideology.
I use a standard DID chain on all my 550s. (Yes, I tried an oring chain.) A worn sprocket will quickly wear a new chain. It's a trade off; economy vs wear duration. For me it works out this way, starting with a new chain and both sprockets you will get the longest wear life. Replace just the chain when worn. 2nd chain replacement, also replace front sprocket, third chain wear out, replace both front and rear sprockets with new chain.
Re-tension a new chain at 200 miles and then 500 mile intervals thereafter.
Chain gets lubed at least every 500 miles. I do mine every 200 with PJ Lube in the black can. Do this at the end of a ride when the chain is warm, and let the lube thicken over night for minimum fly off. Fly off is cleaned with mineral spirits. Wax is for oring chains, NOT standard, I don't care if it is, or looks cleaner. You are trading off chain life for looks with dry/wax lubes. IMO
The lube interval is shortened if you ride in the rain or get abnormal dirt/dust on the chain.
Enjoy your 550. They are very well mannered, and quite a joy to drive around. But, they will keep your left foot busy.
Cheers,
