Valve clearances after lapping

[mvalenti]

So i have my engine rebuilt up to the point where i am checking valve clearances. I was careful and labeled everything as to which cylinder and side it came from.

I am getting some really weird numbers, was wondering if this was normal... Dims are in inches(mm). Is this typical findings after a valve lap job?

Cyl. 1. 2. 3. 4
Ex. .000(0.000) .003.(.0762) .000 (0.000) .0025 (.0635)
Shim. .1084(2.7534) .1045(2.6543). .1037(2.634) .1033(2.634)
Int. .000(0.0000) .009(.2286) .005(0.127) .003(.0762)
Shim. .1066(2.7076) .0967(2.4562) .1035(2.6289) .1048(2.6619)

[tkent02]

To lazy to convert it, what is that in millemeters?

[Triam]

Those numbers seem pretty normal. Make sure where there's a lot of clearance that there's not some crud keeping the valve open.

[lemonshindig]

Should be 2-3 thousandths if I remember correctly.

Just adjust the valves. Nothing about those numbers looks weird to me...

[mvalenti]

So im getting anywhere from 0.000-0.009(.229mm) after lapping. Im worried about the (something) holding the valve(s) open. I thought i was pretty careful when i installed the valves and cleaned them and seats. I was thinking of rotating the engine to open each valve and blow compressed air in the ports then recheck. Really dont want to pull the head off.... If i have to do i need a new set of gaskets???

[Ghostgs1]

So im getting anywhere from 0.000-0.009(.229mm) after lapping. Im worried about the (something) holding the valve(s) open. I thought i was pretty careful when i installed the valves and cleaned them and seats. I was thinking of rotating the engine to open each valve and blow compressed air in the ports then recheck. Really dont want to pull the head off.... If i have to do i need a new set of gaskets???

Mark, I wouldn't worry too much, if you were reasonably careful to keep it clean during assembly. Probably a good idea to turn the engine several times to make sure the shims are fully seated, then check clearances again. Blowing air through the valves is probably a good idea. I assume the clearance did tighten up after the cleanup. Ray

[Super]

I just recently finished rebuilding an '83 GR 650 Tempter engine. A twin cylinder bike. Prior to the rebuild, I had all the valves adjusted perfect. After the rebuild, which included new valve seals and a light valve lapping, all the valves had to be adjusted again. I'm sure the new seals and lapping were the cause. I hand turned the crank several times prior to start up and rechecked the clearances too before start up after putting in the correct shims. It turned over first try and is running just fine. You should be good after adjusting the valves.

[Steve]

... After the rebuild, which included new valve seals and a light valve lapping, all the valves had to be adjusted again. I'm sure the new seals and lapping were the cause. ...

Valve seals have nothing to do with clearance.

.

[mvalenti]

Mark, I wouldn't worry too much, if you were reasonably careful to keep it clean during assembly. Probably a good idea to turn the engine several times to make sure the shims are fully seated, then check clearances again. Blowing air through the valves is probably a good idea. I assume the clearance did tighten up after the cleanup. Ray

Thanks, im not as worried about the tight ones as i guessed they would have gone that direction. The loose ones scared me. I will oil everything up and turn the motor a bunch. Then give you shout for new shims.

[Ghostgs1]

Thanks, im not as worried about the tight ones as i guessed they would have gone that direction. The loose ones scared me. I will oil everything up and turn the motor a bunch. Then give you shout for new shims.

Mark, I didn't notice the .009" at first. Doesn't seem possible if they all stayed in the same locations. I have had some valves act sticky until oil worked it's way in. Hopefully that will be the case here. Ray

[Super]

Hey Steve...thanks for clearing that up. It was my first engine rebuild and I was totally guessing that the new seals and the valve lapping together may have contributed to the valve clearance change. That's good to know for any future engine rebuilds.

Thanks for adding to my ever expanding knowledge base on these great old bikes. It's people like you that make this site as great as it is.

Thanks again

[Steve]

Hey Steve...thanks for clearing that up. It was my first engine rebuild and I was totally guessing that the new seals and the valve lapping together may have contributed to the valve clearance change. That's good to know for any future engine rebuilds.

The lapping process might change the clearance a little, and if it does, it will decrease, as the valve sits a bit lower in the seat.

With the extra clearance that was noted, I would guess that there was some grit stuck on a valve face, holding it open a bit.

The seals only close up the gap around the sides of the valve stem and have nothing at all to do with what happens at the end of the stem.

.

[mvalenti]

oil can in hand, filed with, errr... oil... rotella... will give ports a good blast with compressed air then going to squirt this weekend after the *******... wait... thats not what I meant.. squirt oil....

[mvalenti]

Still getting obscene clearances. Thinking of taking the head off and cleaning everything up, checking for crud keeping the valve open or spring hanging up. Will I need to replace the new head gasket? Its of the layered metal type.