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GS550 Head Swap Questions

  • Thread starter Thread starter leecatd8209
  • Start date Start date
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leecatd8209

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Missed a shift last night that led to a pretty good over rev. Managed to spit and sputter home, and now today she won't run. 0 compression on cyls 2&3, and pretty low on 1. My bore scope showed definite exhaust valve contact across all 4:



I picked up a loaded head, NOS head gasket, and a cam chain tensioner gasket because mine is leaking. Anything else I should pick up? Tips, tricks, mods, advice for while I'm in there?
 
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steveb922 said:
Plan on replacing the base gasket while you're in there.
Click to expand...

I really didn't want to take the jugs off. Is that necessary? If I have to go that far I'm gonna end up doing way more down time than I can afford at the moment.
 
You will disturb the base gasket when you pull the head no matter how careful you are so yes, it is very necessary unless you are willing to have some good leaks
 
Then I might as well do pistons and rings while I'm in there... :nightmare:
 
That picture shows a pretty good impact on the piston. I'm not so sure that I would run them in <my> bike. :-k

And yes, if you don't replace the base gasket now, you will do it in another two weeks, along with all the other gaskets (again). :-\\\

.
 
Alright, so my parts ordered list has expanded to include a base gasket and O-rings, piston rings, and everything to rebuild the tensioner while it's off. I'm gonna hold off on pistons, hopefully I can polish down the high spots to avoid any heat risers, but if they're too bad I'll try to find a set.

Thanks for the help!
 
It's not the high spots and heat risers I would worry about.

The impact might have induced a stress fracture that will develop with elevated temperature. :-k

For some reason, the cracks never seem to weld themselves together when the temperature goes up. :-\\\

.
 
The pistons will be okay. Just inspect them for cracks when you pull them out.

Be sure to remove the valves from your new head and inspect everything. Lap valves as necessary and replace the valve stem seals. Viton seals are best, aftermarket, but most aftermarket gaskets are crap. Best to stay OEM for those.
 
Steve said:
It's not the high spots and heat risers I would worry about.

The impact might have induced a stress fracture that will develop with elevated temperature. :-k

For some reason, the cracks never seem to weld themselves together when the temperature goes up. :-\\\

.
Click to expand...

That's what dye-pen is for.
 
Nessism said:
The pistons will be okay. Just inspect them for cracks when you pull them out.

Be sure to remove the valves from your new head and inspect everything. Lap valves as necessary and replace the valve stem seals. Viton seals are best, aftermarket, but most aftermarket gaskets are crap. Best to stay OEM for those.
Click to expand...

I didn't consider valve seals, now would for sure be a good time. Thanks for the reminder!
 
hannibal said:
Why do you need to replace the head? I guess the piston to valve contact destroyed the valves guides and head?
Click to expand...

Mine has some questionable crack repairs in it, and it was much cheaper to buy a serviceable head than just valves, plus it came with spare covers, cams, buckets, shims, etc. I'll use whatever's in the best shape from both.

Everything looks very good in the spare, and if it specs out I'll just be able to replace it as a loaded assembly to save some time and aggravation.
 
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Just checking in to let everyone know that the top end rebuild went great! I used a serviceable head and pistons, new rings, valve seals, gaskets, o-rings, lapped all of the valves, and got it broken in today.

It runs many many times better, idles fantastically, and overall just behaves much more manageably. I suspect there's been a compression issue for some time.

Thank you to everyone for all of your helpful tips and advice, much appreciated! :beer:
 
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