Topic: Cb550f piston question

[timmangan]

I am in the middle of a project and part of it includes making sure my engine is up to speed.

I have pulled it apart and am just wondering if it needs new pistons or just rings. I figure even if it doesn't need pistons I'll do the rings anyway just because its apart.

I have attached a few pics. The heads of all the pistons are covered in thick black stuff. Carbon in assuming?

I cleaned one of them, and apart from the black junk, they actually all look really nice.

The rings are pretty loose in them but not sure how well fitted they are meant to be.

Any thoughts?

Any more info I can provide for anyone that would help?

Cheers

[Frostyboy]

The only way you're going to work that out is to do some measurements. Ring side clearance, end gap & piston to bore clearance.
You can find the specs in the manual available here
http://i.minus.com/1378357268/Od-7xKVws_qmaG1c6OZ6bA/dbhLYiWZunqkj1/Honda%20CB500%20Four%20CB%20500%20F%20Service%20Repair%20Manual.pdf on pages 27 & 141.
The other thing to consider of course is how many miles/km has the engine done? My 550F has 113,000 km on it & still runs strong with no smoke. Some here love to give the barrels a hone/deglaze prior to reassembly, someone else will chime in I'm sure.
Now that you've cleaned one piston crown you're probably committed to doing the rest. Some say cleaning the carbon off without replacing the rings or honing results in a smokey engine, but I'll leave that to others to debate.
Cheers.

[dave500]

the rings are loose and spin around the piston when out of the bore,pull the pistons off the rods,pull the rings and run a 1mm drill bit through the oil feed holes,they will be gunked up,check the piston to bore clearance,insert a ring squarely and check its gap,hone and re ring or use the old rings if they are good,re lap the valves and replace the valve stem seals aswell,download the manual somewhere on here,it has all the specs you need etc.

[Vinhead1957]

The heavy carbon on top may be oil from the valve seal getting by and burning in the chamber.