81 GS550T Possible top end rebuild questions

[550T]

Hey! I'm new to the forums and found this place to be a tremendous help so far. I have used the search feature every day for the last month to figure out various answers. About a month ago I bought an 81 gs550t in non running, but good condition. I have completely rebuilt/cleaned the carbs and got the bike running.
I have completed a compression test and cylinders 1-3 range between 85 and 98 psi. Cyl 4 is 128.
I'm confident in my mechanical abilities, but need some help/answers from those who have been there. Im considering a top end freshening with new rings, gaskets, valve guides, etc. Plus Im going to drill out a few broken exhaust bolts.

Okay, now for the questions.
1) If any valves need replacing, are the intake and exhaust valves identical. Bikebandit has the same part number, but two different prices.
2) How difficult is it to replace the valve guides? Or should I just take the head to someone and have it machined? Im not looking to increase horsepower, just bring it back to new.
3) Am I missing anything? Gasket set, rings, valve guides, and lots of pentrating oil.

Thanks and sorry for the novel!

 

[Guest]

Hey! I'm new to the forums and found this place to be a tremendous help so far. I have used the search feature every day for the last month to figure out various answers. About a month ago I bought an 81 gs550t in non running, but good condition. I have completely rebuilt/cleaned the carbs and got the bike running.
I have completed a compression test and cylinders 1-3 range between 85 and 98 psi. Cyl 4 is 128.
I'm confident in my mechanical abilities, but need some help/answers from those who have been there. Im considering a top end freshening with new rings, gaskets, valve guides, etc. Plus Im going to drill out a few broken exhaust bolts.

Okay, now for the questions.
1) If any valves need replacing, are the intake and exhaust valves identical. Bikebandit has the same part number, but two different prices.
2) How difficult is it to replace the valve guides? Or should I just take the head to someone and have it machined? Im not looking to increase horsepower, just bring it back to new.
3) Am I missing anything? Gasket set, rings, valve guides, and lots of pentrating oil.

Thanks and sorry for the novel!

Do a valve adjustment and ride the heck out of it and see if your numbers go up. I mean flogg it hard! Bikes that sit awhile need to reseat the rings and valves.
Guides are pressed in.

 

[almarconi]

I think before making any rebuild decisions, do as chef suggest and ride the bike.

How did you do a compression test? Was the bike hot, WOT, etc. Did adding oil to the cylinders change compression numbers. How about a leak down test, did you do one?

 

[550T]

I warmed the motor for the a few minutes, took out the spark plugs, and then ran the test on each cylinder. I will do what you guys have suggested and ride it hard, then check again.
Tonight I am going to drill out the exhaust bolts that have broken off. Not looking forward to this!

 

[Nessism]

I warmed the motor for the a few minutes, took out the spark plugs, and then ran the test on each cylinder. I will do what you guys have suggested and ride it hard, then check again.
Tonight I am going to drill out the exhaust bolts that have broken off. Not looking forward to this!

Make sure you centerpunch the bolt first and start with a small drill bit in the dead center of the old bolt. Work your way up to a larger bit and again, make sure you stay in the center. Most problems occur when people try eazyouts, which tend to break off inside the old bolt, or if they get off center and damage the aluminum threads in the head.

Good luck