Topic: CB550, rebuilding top end, necessity to replace base gasket?

[matic00]

Hey all,
So I'm stripping the old 76 550 down to freshen her up a bit.  I've done a lot of work on her over the years, but have (until now) avoided digging too deep into the engine.

I have a complete gasket kit and pulled the top end off this weekend, lapped the valves, cleaned everything up and am getting close to putting her back together.  This question may be a little naive, but it is a necessity to replace the base gasket since I've taken the head off?  I've seen a debate on the forum about replacing the rings if you remove the cylinders... which I'd like to avoid replacing them as it's a relatively low mileage, good condition bike.

Pros, cons?  Suggestions, input?
Thanks!

[NickC]

Shortly after a recent rebuild, I pulled the head off mine. I can't remember why now, but I do know my base gasket leaks.  I would replace it while the hard work is done.

[chimmychong86]

If you have already spent the money on the gasket kit why wouldn't you replace it?  Is it 100% necesisarry, no. But you already spent the money on the part so you might as well replace it and ensure that everything is fitting well and in the best condition possible. 

[Gordon]

Make that three votes for yes.

Why run the risk of having a leaking base gasket after you've done all that work already?  As for the rings, there's no reason to replace them just because you've removed the cylinders unless they're worn out and need to be replaced anyway. 

[matic00]

Ok cool, thanks for the input guys, sounds like I'll be replacing the base gasket as well.  I was reading through a post and there was a debate about replacing the rings when pulling the cylinders off, so I just wanted to double check on that.  This site is such a great resource, thanks again!

[chimmychong86]

Check the limits on your pistons/rings if its within tolerance and everything looks solid then they don't need to be replaced. If they look worn/ scrapers not looking good replace them. Once again you're already in there do the work right the first time and you won't have to go back in there for a while.

http://data.sohc4.net/SM500/HSM500550_10.pdf

[matic00]

Thanks Chimmy, I appreciate that pdf doc, it'll be nice to have all the specs in one doc like that.

Definitely makes sense to take care of it while I'm in there.  Thanks!

[luap]

agree with the other guys also. what gasket kit did you get for it, Vesrah has my vote, athena tomuch  for the extra parts you get an a cheapy will only have you tearing the motor apart, Id say do the rings also service honda 4 sets for 130.00 i didnt think that was to bad for oem parts

[matic00]

Hey Luap, I ended up getting the Vesrah, read nothing but bad things about the Athena.  Picked up the Vesrah from TAS for like $74 which was cheaper than anywhere else I could find.  I'm definitely going to check the tolerances of the rings, etc.  I don't have any experience with honing the cylinders, but I imagine that should be done if one were to replace the rings?

[vance]

I got away with not replacing the base gasket and it didn't leak. However I didn't pull the jugs off so I was able to just replace the head gasket and the 2 oil galley o rings

[luap]

74.00 is good price glad to hear you got your parts from them Ive tried ordering twice now just to wait 2 weeks to get a refund.

[73hutch]

I got away with not replacing the base gasket and it didn't leak. However I didn't pull the jugs off so I was able to just replace the head gasket and the 2 oil galley o rings

+1