how to clean valves properly

[RBoss]

Hi all,

After rebuilding and painting the engine to replace primary chain + rubbers, I am now at the stage of rebuilding and assembling the cilinder head.

I am planning to (lightly, they are in pretty good shape) lap the valves and replace the valve stem seals. I have bought the lapping compound and the suction cup tool and am looking forward to this job. Before starting on that though I want to properly clean the valves from carbon etc.
I have watched several videos on how to clean the valves and on that basis I started cleaning the first exhaust valve by spinning it in a cordless drill using a scotchbrite pad/brass brush to clean the valve (see picture for the result). After cleaning the first valve I had the feeling there was some sort of coating on the valve. My question;

- have I done irreparable damage to the first valve or can I still use it?
- what is the best way to proceed with the other valves?

Pictures:

1. engine in restoration proces
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2. exhaust valves
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3. inlet valves
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Thanks!
Ruben

[RBoss]

Extra zoom in on the "scothbrited" valve on which I might have done some damage.
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[Bryanj]

To the best of my knowledge standard Honda valves have no "coating" although the tips may be stellite.
The valve seating area on the valve you show does look to be pockmarked and as these faces are not supposed to be machines only lapped you may have a problem getting a decent seal

[RBoss]

To the best of my knowledge standard Honda valves have no "coating" although the tips may be stellite.
The valve seating area on the valve you show does look to be pockmarked and as these faces are not supposed to be machines only lapped you may have a problem getting a decent seal

Thanks for your quick thoughts Bryanj. I am not very worried for a bad seal as there where no problems (to my knowledge) with it before I opened up the engine. I still have to lap the valves with compound so that might also make it better.

Any advice on how to clean the valves/take of the carbon?

Cheers,
Ruben

[Bryanj]

Soak in paraffin or similar then the scotchbrite

[Nurse Julie]

The valves look like the seating are burnt. It is advisable to re- face the valves and re-grind the valve seats. Check the valve guide to valve stem clearances are within spec.
We find a good result de-coking valves by soaking in thinners for a day and wipe off.

[RBoss]

Thanks for the advice!

The valves look like the seating are burnt. It is advisable to re- face the valves and re-grind the valve seats. Check the valve guide to valve stem clearances are within spec.
We find a good result de-coking valves by soaking in thinners for a day and wipe off.

@ Julie what is een-facing the valves?

[Nurse Julie]

Thanks for the advice!

The valves look like the seating are burnt. It is advisable to re- face the valves and re-grind the valve seats. Check the valve guide to valve stem clearances are within spec.
We find a good result de-coking valves by soaking in thinners for a day and wipe off.

@ Julie what is een-facing the valves?

Do you mean re face?

[RBoss]

Do you mean re face?
[/quote]

Yes! Autocorrect on a smartphone…

[McCabe-Thiele (Ted)]

FWIW except when I have had to have new valve guides on car cylinder heads  I have found most valves will seat ok by just going throught the two grades of grinding paste. Coarse to remove the worst bits then fine for the final seating. It's tedious but I've always managed to get the surfaces back to where they should be. Professional engine r-ebuilders often re-face the seats as it's more cost effective but if your labour is free then its worth a shot.

It's time consuming but unless you have serious pock marks on the seating face they usually clean up okay. Your fist grind with coarse paste will usually reveal if the pock marks are too deep so need re-facing.
 

[AshimotoK0]

FWIW except when I have had to have new valve guides on car cylinder heads  I have found most valves will seat ok by just going throught the two grades of grinding paste. Coarse to remove the worst bits then fine for the final seating. It's tedious but I've always managed to get the surfaces back to where they should be. Professional engine r-ebuilders often re-face the seats as it's more cost effective but if your labour is free then its worth a shot.

It's time consuming but unless you have serious pock marks on the seating face they usually clean up okay. Your fist grind with coarse paste will usually reveal if the pock marks are too deep so need re-facing.

Ideally though on Honda's Ted,  there is quite a tight spec. on the seat width..so that should be watched out for.

[RBoss]

Thanks all for the advice!

I think I will starts soaking the valves in thinner or similar, clean them with scotchbrite and proceed with both the valve lapping pastes in the lapping procedure. Like you say Ted, I don’t mind spending time on a tedious job. That’s the reason I am in rebuilding this amazing bike anyway 

Thanks,
Ruben

[Seamus]

There is a tool for lapping valves. Fits in a battery drill and it oscillates the valve. Saves loads of time and sore palms.
Had mine for about 35 years and still going strong. They have something similar on Amazon for about 20 quid

[deltarider]

Hope someone can teach me on this. Is it true that some valves are special and are not supposed to be lapped and if you do, you will do more harm than good? Second question: what is it precisely, that causes valves to wear?

[RBoss]

Hope someone can teach me on this. Is it true that some valves are special and are not supposed to be lapped and if you do, you will do more harm than good? Second question: what is it precisely, that causes valves to wear?

Additional question to this, what would make the valves special (do I have them?  )