1979 suzuki GS550 lap the valves or not?

[charlie27]

hi,

I picked up a 79 GS550 several years back with a head gasket leak. I now have the engine torn down. I was thinking I would lap the valves and hone the cylinders (lightly). I have removed carbon build up. Engine has about 6k miles.

Lots of opinions on valve lapping and benefit versus actually doing nothing or making worse. Newer technology has coating on the valves and a definite no.

what are the thoughts on these engines?

TIA

[Nessism]

Main thing you really should do is to replace the valve stem seals.

Lapping the valves lightly is fine and mostly just to clean them and verify you have a good contact patch on the seat. Do NOT lap the valves aggressively, that's where the problems come in; you can create a ridge in the valve which is bad.

[one_civic]

Use fine lapping compound and do them by hand, not with a drill. As Nessism said, you do not have to go too hard or very long, just make sure you do not get any lapping compound inside the valve guide and splurge on some Viton valve stem seals.

[ukjules]

Lap the valves and new oil seals and your bike will be transformed ! (if you add all he other obvious tuning too)
I did mine with a drill ---- but reading all this i wont again. I survived mind.
I only used a drill as my lapping stick was useless and would not hold the valve firmly enough.