I think I can re-shape a wrench, 10mm I believe?. If I understand the proceedure, I loosen the gear, remove the chain, then slide out the cam shaft. I have a question, how do put the cam and gear back so that you're close to it's original position?? One other question, someone said that with the engine sitting for so long, all the internal rubber will be dry rotted and need to be replaced. What am I looking at as far as cost. This is saying that the heads can be cleaned and pistons, rings, valves are not bent or burnt, just replacing all the seals and guides OR, having the top open, would it be best to just do a complete overhaul?? I would commit to doing this for the experience and learning but money will be an issue for me. Thanks again.
10 mm going by memory from a long time ago.
Here are the steps.
Remove the chain adjuster assembly from rear of cylinders.
Back off all the rocker adjusters.
Remove the rocker shafts.
Get the 2 cam gear bolts out.
Move the gear across and off its resting area on the cam.
Drop the chain off the gear.
Weave the cam out through the gear slots.
Be ready to move the gear and cam to align for easier passage.
Retiming the cam is easy.
Set the crank at the T mark on the ignition breaker plate re cylinders 1 & 4.
550 details at the top are not known to me, but should be same or very similar to the 750 design the 550 is very similar to.
Look for a three marks on the end of the cam, two should be on the horizon with the third vertical and positioned at the top.
(this looking at the rocker arm box from the side of the engine and at the end of the camshaft)
It's easy work.
Oh yes, if the 550 is like the 750, when you are removing the head, DON'T miss first removing the 4 small bolts that hide below the 4 rubber plugs beneath the rocker boxes !