Question about '81 XJ650 cyl. head

hello all,
I took the cylinder head off my '81 XJ650 Maxim since the head gasket was leaking at cyl. #1. Also, the bolt holes for the exhaust headers are pretty chewed up.
I have a couple of questions. The head is filthy and I've cleaned the heavy crap off it pretty good. But how do I get it clean in all those nooks and cranies in between the fins and so on?
Also, would it be better to tap and thread larger bolt holes for the exhaust headers or tap the holes out and insert helicoils?
I prefer to tap and thread since I'd like to insert studs and then use nuts to hold the exhaust headers to the cyl. head rather than chewing up the bolt holes everytime the headers go on or off the bike.
One thing I'm worried about is the amount of material in the bolt holes on the cyl. head. They protrude from the head and stock, the holes are 6mm. If I open them up to 8mm that doesn't leave much material.

Something else I did that I read about was a solvent leak test in the combustion chambers. With the valves in place and spark plugs still in the head, I filled each combustion chamber with WD40. Not a drop leaked from any of the four combustion chambers. This would lead me to believe the valves and valve seats are in good shape and a valve job may not be required. Does that make sense?

Thanks in advance for any comments, advice, etc.

baz

 

I would encourage you to helicoil the exhaust port stud holes. Much better idea and stronger too.
Sounds like your valves are good to go.

 

a good practice is to only go up one step at a time, something like
new studs in the same hole (Mcmaster- Carr)
drill for insert of same size (6.2mm i think)
drill and tap next size
stainless nuts on a stainless stud will work for a very long time

 

Studs with nuts on them was the original configuration, if it was different someone did it.

I agree with Robert; if the holes aren't sound then Heli-coil them and use the stock size.

It does sound as though the valves might be fine.

 

thanks for the help, guys. I'll be going with helicoils and then insert stainless studs and stainless bolts to hold the headers on. I didn't realize that studs were the original factory config.
thanks again,
baz

 

Any one got the measurement for those exhaust studs? I am assuming they are 6mm diameter but how long and what thread pitch?

 

Good question.