Valve clearance questions dohc

[slownugly007]

Hey guys,
Im working on checking the valve clearance on my bike and came up with the following measurements in inches, sitting on the bike left to right:

Exhaust:

1) .004", 2) .004", 3) .003", 4) .003", 5) .002", 6) .002", 7) ~.006", 8) .004"

Intake:

1) .004", 2) .005", 3) .005", 4) .005", 5) .004", 6) .004", 7) .002", 8) .002"

According to many DOHC sites, .005" is the ideal clearance for both Exhaust and Intake. My problem is that the shims I can purchase are only in .05mm (~.002") increments, so my question is: Is it better to be high or low on my clearances since I can only make adjustments in .002"?

Thanks guys!

[TOOLS1]

It's better to be high then low on your valve adjustment clearances. You definitely want the valve to close completely, and it is when the valve is closed that it releases it's heat into the head. With today's crapy gas engines run hotter then they did 30 years ago.
TOOLS

[slownugly007]

Awesome thanks tools!

So do you know what would be a good range? Since most sites claim the .005" is ideal, would +/- .001" be sufficient?

[TOOLS1]

If they were that close, I would be doing a happy dance, if I were you.
TOOLS

slownugly007 wrote

Awesome thanks tools!

So do you know what would be a good range? Since most sites claim the .005" is ideal, would +/- .001" be sufficient?

[slownugly007]

 

you think the .002" might need to be loosened up some? Maybe I can swap some shims around to even them all out

[Hoosier Daddy]

.005" is prefered +/- .001" so that gives you a range of .004" to .006" , lean to the high side.
Also experiance shows it is not an exact science when figuring shim changes. You will need to reverify once the ESTIMATED change has been made.

[slownugly007]

thanks hoosier!

Im gonna shoot for .005" or .006", when I checked clearances I moved up by .001" on feeler gauges until wouldnt slide in, some would go in with a larger feeler gauge but  would need a good bit of a push to get in there...almost tight? Is this what Im looking for or does it not have to be that tight/exact as long as its withing .001"?

example: on the one that measured .006", a .005" feeler gauge would go in with a little drag but I was able to get a .006" feeler in with a little wiggling and more drag.

Thanks again guys!

[TOOLS1]

You just want a little drag on your feeler gauge.
TOOLS

[Johnnylevi]

sorry to high jack this thread, but when you guys say high end what does that mean? more clearance or less clearance?

[TOOLS1]

More clearance.
TOOLS

[Lucky 1]

You want them LOOSE,for the reason TOOLS1 mentioned.

[Hoosier Daddy]

When I set valve (or any) clearances I use the "Go-No Go" method. In this case get out a .004, .005 and .006 feeler gauges. Start out with .005 should go, but a .006 wont go. Optimally you should feel a slight drag on a .005"  If I find a .005 is maybe too snug, double check that a .004 is loose.
If all these apply then you are good.
 Also, just as a heads up... the factory had "half size" shims available. These ended in a 2 or 8 that filled the gap between whole sizes, made it easier to dial them in, but their Parts program didn't offer these to the public. You can find them on e-bay every once in a while but they aren't as common as the standard whole sizes.

[FastCletus]

So I am understanding correctly.  .005 on intake AND exhaust is optimum?

[Chip]

I have a 81 cb900c. Rebuilt the engine and cylinder head.i have a question about the calendar head.i bagged and labeled all the valves and parts so to put them back in the same hole the same out of. All I did was hand lap the valves. When I whet to reassemble after installing the cans
 Some of the valve shims were way off, I had to surface grind as much as 30 thousand off them to get the 5 thou clearance. What could have possibly happened

[TOOLS1]

They could have been off that far before you took the valve train apart. I hope that when you installed the surface ground shims, you put the ground side down towards the shim bucket.
TOOLS

[Tjhill]

Here's an odd one for you all. Now, I'm new to this thread, and I just bought a 1982 CB900C. I'm somewhat new to the bigger CB's. The guy I bought it from put in new shims, but gave up when, after putting in the shims the motor would only crank about 350 degrees back and forth as if the #3 piston is hitting something at TDC. I removed both cam shafts in case he overshimmed, but it still wasn't quite hitting TDC. The odd thing is that the right hand exhaust valve on the #3 seems to be actually sitting higher than all the rest of the valves, so visually that looks like the problem. When hand cranked though, the clunk when the crank stops sounds like it's maybe at the chain from the crank to the primary. Not looking for online diagnoses, just wondering if anyone else has had an issue like this, and if they may know where to start other than obvious "tear the top end off and see if that valve isn't seating properly". Also does it seem wiered that one valve would be sitting higher than the rest? I mean, if it were holding a piston off TDC, shouldn't it be lower?

Thanks sorry about the high-jack, more meant as a segue!

[TOOLS1]

A valve should not be noticeably higher. As for the cam chain stopping the engine from rotating 360*, yes it can do that if it drops off the sprocket at the bottom and jams it up. However it does sound like a tear down is in order to figure out what is going on with the valve.
TOOLS  

[Tjhill]

 Yeah, I just bought it a couple days ago, and all I've had time to do was down to the sprockets pulled from the top end. I do have a funny feeling that once I get down there, I may find that the previous owner may have dropped a shim down there and thrown the chain off. The only reason I don't think it's that is because it stops in the exact same spot, with absolutely no play, and no grinding everytime, which tells me it's something that's comletely immobile, maybe something to do with the clutch not actually dissengaging in neutral, I haven't tried turning it while I roll the bike yet. Right after I try that, for sure full teardown.
 Thanks for the advice