AIRHEAD VALVE ADJUSTMENT with Pics

I know the valve clearance is supposed to be checked every 5000 miles, but I'm wondering how long some of the valves have stayed within spec. Does anyone have any records to show valves have stayed in spec for 15 or 20,000?

 

Sort of.

I keep log books on all of my bikes; and I can tell you this: They do seem to "settle down" such that they don't get out of spec on every check, but they do change albeit slowly. I would say that "staying in spec" for 10,000 might happen; but generally not 15K or 20K.

You have to remember that "in spec" is a range and it depends on where "in the range" any particular valve was the last time it was checked.

If you check them every 5000 miles, you'll end up shimming maybe one or two, or maybe even none, depending on how close any particular valves were to being out of spec the previous time.

The key is to check them every 5000 miles.

carbonxe the "tool" doesn't work if it's not centered on the cam lobe; I covered this in detail in "Part 2" where I also explained the "zip tie trick." I never have a problem either, but I know the "secret."

 

Ive been looking for this post for hours!!!

 

BigFitz.... I love your write ups... I'm gonna have to do this

 

Thank you for this write up!!

I was intimidated by this job for a while whenever I saw it referenced in the forums. After reading this one, I went and bought some feeler gauges and did the measuring in decent time.

One confusion though, on my cyl #4, I took a measurement of .076mm for the intake. I popped out the shim, and it is a Y270. I look at the chart, and, em...? There is no suitable replacement?

EDIT: Nevermind... found my problem with numbers. (was looking for .7 instead of .07) Don't blame me, I was raised in the south! ;o

 

i cant seem to find feeler gauge with proper gauged fingers, does anyone know how much the intake and exhaust for all valves cost? think it be best to go ahead and place new one in and call it a day, oh and where can i get that valve compression tool that is shown in the pics.

 

Metric Feeler gauge: KD tools' 2274 http://www.google.com/products/catalog? ... DAQ8wIwBQ#

You can't buy shims until you measure the clearance, and if out of spec, see what is installed. There is no "standard" size shim, bikes straight from the factory have different thicknesses of shims on different valves.

I'll say it again: SLOW DOWN, go back and read this thread carefully it explains in detail exactly what to do and in what order. You can't "skip ahead." There are no shortcuts. You can't just buy a pile of shims, they come in like 15 different sizes.

 

Great post, thanks

Just a small note, that made me having a few sessions of bad words. Rotate bucket before placing tool, so shim can come out. Took me a few mins to figure that one out.

Maybe put that in there in the text on first page ?

 

What is the benefit of the valve adjustment?

 

Major benefit ! Probably the biggest 'must do' on these bikes. If your valves are out of adjustment, you could have loss of compression, valve damage and associated engine damage. It's an easy, routine maintenence 'must do' - just like changing the oil and filter. Doesn't take long to do and you don't need any specialized tools to do it.

 

mmmm Must do! I love to work on my bikes the problem is that I dont have a garage and sometimes....just sometimes is a real pain in the butt!!

Oh well! Gotta do it! Like is would say in spanish " Ni pedo " LOL

 

"Because you have to" isn't much of an explanation.

The valves are operated by the cams pushing on (shimmed) buckets that ride directly on the top of the valves themselves. As the valves "pound" themselves into their seats over time, the clearances in the valve-actuating mechanism tighten up. They can eventually tighten up to the point where a valve is not being allowed to close fully; at which point the damage begins.

Adjusting the valve clearances involves restoring the specified clearances between the various moving parts so that the valve train operates as designed.

This is equally important because the amount of time a valve spends open versus the amount of time it spends closed affects things like compression and manifold vacuum. Since the XJs are equipped with CV carbs, which are in effect vacuum operated, keeping the valves in spec greatly affects carb tuning as well.

 

I overshot the number on a shim I ordered, and now the exhaust clearance is 0.26mm, will it be a bad idea to run with this?

 

Not a good idea, that's for sure. Loose IS better than tight; too loose is risking spitting a shim. I wouldn't.

 

Here is my contribution to the cause.

It is useful!!

 

It is already in the article, too. About the 19th pic down from the beginning; and a tad easier to read. Thanks though...

 

That's right. I just put togeher the chart and on top there is aplace where you can take notes of your measurements.

Is there way to upload excel docs?

 

I just measured my clearances and got the following measurements:
Cylinder: 1 2 3 4
Exhaust: .006 .009 .007 .008
Intake: .006 .004 .006 .004

However, when I put my caliper on the feeler gauges they measure slightly bigger than they claim to be. The .004 measures at .0045, the .006 measures at .0065. This is important because depending on which measurement I go with determines which of the two intakes I need to swap out as well as determining whether I need to swap out #1 exhaust (.004' = .1016mm, not in spec, whereas .0045 = .1143, in spec; the problem is the opposite for the other two intakes which are in spec at .006 but not .0065).

So my two questions are as follows:
Which of these measures should I trust?
Are any of these so out of spec that they run the risk of damaging the engine if I continue to drive it for the next couple of weeks while I await my valve holder tool and then a couple more while I await the appropriate shims?

P.S1: I realize I need a set of metric feelers. I thought that is what I had bought since that is what they were advertised as. But like the feelers many of you are using, it is only a s***ty metric conversion feeler and the conversions are not very precise.

P.S.2: Sorry to drag up an old thread, but this is a good one that could always use a bump anyways.

 

Speaking as a machinist, calipers shouldn't be trusted closer than about a thou. If you really want to make sure the feelers are right check them with a micrometer.

I'm doing my 650, and got the following measurements:

Cylinder: 1 2 3 4
Exhaust: .005 .005 .007 .005
Intake: .0025 .004 .005 .003

My question is if it would do any harm for me to dust the shims off on my surface grinder to bring the clearances in spec? I'd grind the bottom side of course so as not to alter the surface finish on the top side.

 

Wow! I tell ya what, if you're thinking about doing your shims, stop thinking and just do it! I ground the shims to the midpoint of spec, put everything back together, and took her for a little spin. She sounds way different, a lot less clinking and a lot more base, and has WAY better power and response. Now I just have to break out the Colortune and tweak her in.