Topic: new valve seals ruined?

[elquenada]

i was installing my freshly lapped valves when I realized I put the first two in the wrong place. I removed them and had to pull the valves back through the seals.  I seem to remeber reading on an older post (perhaps a Hondaman post?)  that once the valve lip passes through the seal it ruins the seal.  Is this correct or am I going crazy?

[MRieck]

The sharp, upper edge of the keeper groove can easily tear the seal.

[elquenada]

so are you saying I should replace them or is it something i would be able to see?

[elquenada]

can anybody else weigh in here?  is this something I need to feel out or should I just ditch these seals once I have pulled the valves back through them?

They looked fine last night so I just reassembled using the correct valves but I dont want to close up the bike just to have to tear it down again.

[MRieck]

 I would replace them but that is me. Better safe than sorry especially after going through all that work.

[MCRider]

can anybody else weigh in here?  is this something I need to feel out or should I just ditch these seals once I have pulled the valves back through them?

They looked fine last night so I just reassembled using the correct valves but I dont want to close up the bike just to have to tear it down again.

I've done that before, and run the same seals. Not because I knew they would be all right, but because i didn't know any better. Turns out they were all right. But that's the risk.

I defer to MRieck with these addtl comments.

The original CB750 didn't even have seals on the exhaust, so if they were exhausts you could be a little more comfortable keeping them.

Intakes... it could be smoky if they are damaged. The pistons are trying to suck pretty hard on the downstroke and will draw oil in if they can.

[elquenada]

thanks for the input.  I'll have to mull this over but I think I may just replace them with some vinton seals.  i dont want to have to open the head a second time.

[MCRider]

thanks for the input.  I'll have to mull this over but I think I may just replace them with some vinton seals.  i dont want to have to open the head a second time.

I bot the Vinton from eBay for my current project's intakes. I'm leaving the exhausts off, harking back to the original.

[elquenada]

thats a 750 right? do you have to have special valve guides to that or are all 750's like that?  I have 550 but im just curious.

[MCRider]

thats a 750 right? do you have to have special valve guides to that or are all 750's like that?  I have 550 but im just curious.

Yes mines a 750. I got hold of the original exhaust guides which do not have the end to hold a seal. They are shorter and taper to an edge. Less friction.

One could simply leave the exhaust seals off of any guide with the machine lip, if one wanted to.

This is one of HondaMan's many tips on how the later 750s lost horsepower over the originals. Bit by bit. Every little thing chipped away at the original's edge.

Mine may smoke a tad,  but I was around when the first ones came out and I don't remember any smoking. And if anyone notices I'll tell them why.  

If you think about it,there is little opportunity (though there is some)  for the piston to draw oil down the exhaust guide, its mostly pushing exhaust gasses out. And any oil it does draw goes out the exhaust, not into the combustion chamber as it would from the intakes.