What do you think of this valve job?

Dear KZriders, I am restoring my 1978 KZ400B and I just finished refreshing the top end with new piston rings and a valve job. Everything was heavily coated with carbon and it took me a lot of effort to clean it up. As this is my first time lapping valves I would like you to take a look at the end result. I did it by hand using fine abrasive paste. I lapped every valve for around 10-15 minutes or whatever it took for the paste noise to become quiet enough.
I am attaching images for each valve and seat let me know what you think!
Thank you.

Never tried to do a valve job myself so kudos for going for it !!!
Did you see if they leak by using a bit of gas down the ports and looking closely fir seeping?
I think there’s a spec’ed width for the contact area , did you measure the contact patch?
I’ll be watching to see what the experts say!

As long as the seat width isn't out of spec and you didn't wear a groove in the valve it should be fine. Personally, I like to find a local machine shop use a centerless grinder on the valves to renew them. It only costs about $4 each so it's worth it.

How much rock is there in the guides using the valves? Looks to me the seat print on the valves are wider than the seats in the head. The ones on the head look good.
Steve

Nessism wrote: As long as the seat width isn't out of spec and you didn't wear a groove in the valve it should be fine. Personally, I like to find a local machine shop use a centerless grinder on the valves to renew them. It only costs about $4 each so it's worth it.

The intake valves seats are slightly out of spec at 1.08 - 1.15 mm, service limit is 1 mm.
I did not know that resurfacing at a shop would be that cheap thanks for the info, but I really enjoy the satisfaction of doing everything by myself so I'd take my chances and test them out.

SWest wrote: How much rock is there in the guides using the valves? Looks to me the seat print on the valves are wider than the seats in the head. The ones on the head look good.
Steve

They match the seat perfectly, but they look wider because in the picture you can see that the new freshly lapped seat is slightly offset from the old one making it look wider. I can't feel any slack between the valve stem and the guide but I don't have a bore gauge to measure it accurately, valve stems are in spec and look pristine.
My only concern is that I can see rings cut on the valve surface by the lapping compound, these are not grooves as you cannot feel them with your fingernail but ideally, I know I would like this surface to be completely smooth and dull, right? I am using fine compound, I wonder if I should look for a finer one.

Sounds good. I'd put it together and RIDE THE PISS OUT OF IT. :woohoo:
Steve

Don’t go crazy with this. Keep in mind that the reason margin dimensions are given are to insure a proper and tight valve to seat seal ... based on the spring pressure vs the total square area of the valve to seat surface area. In other words, pretty and wide “grey” is not ideal for super tight sealing. While skinny will seal tight for a while but wear faster and can cause exhaust valve overheating.

missionkz wrote: Don’t go crazy with this. Keep in mind that the reason margin dimensions are given are to insure a proper and tight valve to seat seal ... based on the spring pressure vs the total square area of the valve to seat surface area. In other words, pretty and wide “grey” is not ideal for super tight sealing. While skinny will seal tight for a while but wear faster and can cause exhaust valve overheating.

got it thank you!. I did not make then any wider but, unfortunately, the intake seats were already slightly out of spec, I believe it will still be OK for now. Next time I will have the seats re-cut and I'll pop new valves in. My only dissatisfaction with this first time lapping experience is that I can see "rings" on the intake valves' lapped surface whereas I believe it should look completely dull and smooth. I am not sure how to correct this maybe I have bought a low-quality compound that does not breakdown correctly in finer and finer grit as I lap the valve.

Here is what I am talking about. If you run your fingernail over it you cannot feel any groove but I believe that's not how the valve surface should look after lapping. If anybody knows how to correct this I'd be happy to learn.

Look for someone with a centerless valve grinder. Good chance those valves will clean up like new.

Nessism wrote: Look for someone with a centerless valve grinder. Good chance those valves will clean up like new.

Funny this video is made by the shop down the street