valve adjustment - 1982 Maxim XJ650

Hello all. I picked up this neglected 1982 xj650 Maxim about a year and a half ago, brought her back to life, rode it around a little last year. The valve cover developed a leak last fall. So, seeking to replace it, I figured I should check valve clearances lest I burn a valve. So I ordered a valve cover gasket, Yamaha part number 16G-11193-00, also says SX20202A 301. This is close but no. This gasket is flat, the one I need is a 3-d molded rubber gasket, with moldings on the ends of the cams.
My first question, is does anyone know the part number for the rubber gasket?

As to the valves, measured clearances, 1-4 are: 0.11/0.155 0.105/0.155 0.135/0.16 0.1/0.16
I was relieved to see that no clearances were exceptionally tight.
I understand that specs are .11-.15/.16-.2. Also that the shims are only available in 0.05mm increments. This technically makes it impossible to bring into spec my #2 intake valve as well as the #1+#2 exhaust.
I'd like to get an idea, from people who have owned and maintained these motors over the years, how much wear to expect between the roughly 5,000 mile scheduled check period?
Also, does anyone know the expansion? or have measured the cold clearance on a burnt valve? I'm kind of thinking I'd rather button it up and revisit it in 5,000 miles or so (next winter).
If that's a bad idea, I'd like to know people's thoughts, or better yet if anyone has experience with, going 0.01mm loose? (0.16/0.21) Obviously you can look at the numbers above and see why I ask. If I'm going to get in there, I'd like for it to be done for awhile. (and likely buy one size smaller for intake#3 and shelve it)
Also, I don't have a tool like specified in the manual to hold the valve open. Has anyone tried, and had luck with holding it down with a piece of plastic or brass?
When I remove a shim is it safe to continue rotating the motor (by hand) with no shim and the cam lobe directly on the bucket, without risking damage while I complete removing the others?

Additionally, now with the cover off, the gasket doesn't look too bad. Has anyone tried shimming the rubber on the bolts to apply a little more force on the gasket?

Thanks to all who take the time to read this.

 

Read this and follow it. In spec is in spec; there is no more/less in spec.
https://www.xjbikes.com/forums/thre...valve-adjustment-with-pics-parts-i-ii.116006/

Order your parts from XJ4Ever and get the right parts every time (logo in the top right corner).

 

well 0.105mm (current) nor 0.155mm (smaller shim) is in spec for an intake valve, nor is either 0.155mm (current) or 0.205mm (next size) for exhaust.

Answers to questions I asked are appreciated. Reading my post before commenting on it is appreciated as well.

 

Don't turn the motor with a shim out it can cause damage.

 

The answer given was correct.

Measuring to the third decimal place is unnecessary as there is no provision (or need) to adjust the clearances to that degree of resolution.
Round all measurements to the nearest hundredth (not necessary when using Metric feeler gauges instead of SAE).

The valves you see as being out of spec are actually in spec. I suggest leaving them be and checking again in 2,500 miles.

In addition to reading the valve adjustment link provided in Kosel's post, you should read the first link that appears in my signature for further information about how to care for your XJ.
You will also want to replace the rubber doughnuts on the valve cover bolts, as they are what provide the clamping force to keep the gasket from leaking. The bolts just hold everything together. Don't overtighten them or you can end up cracking the head casting, because they have a shoulder on them that contacts the gasket flange.

Welcome aboard

 

I understand that the 0.005mm increments don't matter. Just saying that since there's no half size available, that the only two ways it will be technically "in spec" is either: A) consider my 0.005mm feeler gauge to be contraband barred to the depths of hell, or B) round the 5 up. But even rounding up, I'd still have to change one now, so as you say, and yes i understand, that they will wear in, so if I do all 7 that could kinda use it, and end up with 0.21mm on two exhaust valves, how long would be an estimate, from experience, on about how long it would take to wear to 0.20? Likewise I understand that If I button it up with exhaust valves at 0.16 or especially, the ones at 0.155, that checking them 5,000 miles I would expect them to be out of spec. But how much? If the 0.16 will be 0.145, maybe I should leave them. If they'll be 0.13, than I'll have been in spec more of the time if I change them to 0.21 now. I understand valves and have adjusted tappets, ground valve-stems, etc. on other engines. My questions here are engine specific. This is my first bike and I've never been in anything like it.

 

You are splitting hairs that don't need to be split. Being 0.01 out won't damage a valve or cause any issues with running.

Read the link. Use the table. Trust the engineers.

The check intervals are just that, checks. As the engine gets more miles on it you will find that the valve clearances stay in spec longer. Eventually you'll go two or three check intervals without needing to change but one or two shims (if any).

Most of us have found at least one (and some more than one) running XJ with 0.00 clearance on one or more valves. Once put back into spec most of them went on to run as if they had been maintained properly to begin with

You have a very sturdy engine, so don't fret over 0.001 mm, because...

You are using SAE gauges that are stamped with the metric equivalent. Metric gauges do not come in 0.001 increments for measuring motorcycle valve clearances. Just round the 0.005 up, or get set of metric gauges.

 

Ok well then not relating to anything I'm doing, can anyone here share their experiences as to whether they typically see valves wear:
0.02mm-0.03mm per 5,000 miles? 0.02mm-0.03mm per 20,000 miles? X.XX (inch/mm) / X.XX miles/km/revolutions/anything?
This is a site about bikes, I know people that have these bikes work on them, I'm sure someone here has put enough miles on one to know what I'm asking.
I have a few different sets of sae and metric feelers. I have one 0.005mm feeler.

 

0 clearance on a cold valve would have to mean a burnt seat in any case, the degree to which would vary with amongst other things, (one of my main questions), how much expansion at temperature. If it could still seat and maintain proper compression after being burnt like that then that does indeed indicate a very robust valve.

 

Nope. There are no rockers in the system, so a 0 clearance valve is opening less than it would if it were in spec, and staying in contact with the seat longer, resulting in more time for the heat to transfer. Burning of the valve or seat is still possible, but much less likely than in a rocker actuated valve system.

As to your question, how much wear will depend on how many miles are on the engine and how hard it's ridden. I'd expect that an engine with less than 10,000 miles will have had the shims swapped out once or twice for all the valves, but one with 100K might only have had the valves adjusted 5 or 6 times (YMMV).

I've only put around 10K miles on my Seca (money trouble has kept me from traveling as much as I'd like the past few years, and my commute is only 4 miles each way) and have only had to swap shims out on two valves since setting them to spec when I bought the bike. She has just a bit less than 29,000 miles on the engine.

 

How does 0 clearance, not turn to less than 0 clearance at temperature, meaning the valve is held open at all times, letting the blaze of combustion by it, and not allowing it to seat and sink heat?
If clearance is clearance, and 0 is 0, then less than 0 (at temperature) would have to mean valve open. No?

Mine has just short of 20k, I was kind of scared to check, but glad to see that they're all basically within spec.

 

That all depends on how close to 0 it really is. remember, most of us are only measuring to the nearest hundredth. Since the valve will expand in all directions there can be enough contact to save the valve from being burnt, especially if the bike gets parked and then sold because it won't start when hot.

Also keep in mind that most people don't ride very much at all, which limits how much damage gets done when the valve clearances are tight by virtue of not being run in that condition for very long. By all rights every '82 XJ should have over 300,000 miles on it, but hardly any of them do (and at least one member on here has put almost that many miles on one).

Again, YMMV.

 

As I understand it, and I've worked on a lot of engines, not these, but the concept is the same, old flat-head, pushrod, overhead cam.
If you read 0. It got there gradually. Say it was in spec. then 0.03, 0.02, 0.01. 0.005, 0.000001, and finally, 0. Chances are it ran past the point it got to zero, meaning valve open even on the base circle of the cam. Even if it just got there on that revolution, (to wear it to that cold measurement) the expansion of the valve-stem at temperature will make it "less than zero", and the valve doesn't close valve to seat.

Back to my original inquiries, how much the valve-stem expands in length varies with engine design. I'm sure it's much much more on here on an air cooled engine than on water cooled (cooler) engines. The minimum exhaust valve clearance is for the expansion at temperature, plus a generous safety margin, plus wear margin.
I'll probably button it up, and run it, then measure immediately after getting back from a decent length ride on a warm day.

 

How is it possible for you to take a 0.00 clearance cam to shim check back into specifications since it is unclear if you're exactly at 0.00 or negative? I think you'd have to install a smallest shim possible then do a clearance check then do the math to find the correct shim. Please respond, believe i have 1 that i'm unable to identify since it is showing 0.00.

 

When I ordered shims for my X I had a couple or three where I couldn't get my smallest feeler gauge between the bucket and cam. So...I had to order extras in smaller sizes just in case.

 

If the measured clearance is zero, or less than zero, put a shim that is a couple sizes thinner. If the clearance is still zero, keep doing this until you measurable clearance. I know this requires access to a good selection of shims, but it really is the only way.

Good luck

Patrick

 

That does the trick. @chacal sells plastic shims and thin shims for just that purpose.

 

There is another way. See my post above.

 

Sorry, have to poke my nose in here - zero clearance will not mean more seat time - it will be less. Which will ultimately increase the risk of burning. Rockers or any other magic between cam and valve is neither here nor there.
Other than that, I have to agree with @k-moe , stopp worrying about .01 of a mm - its less than half a though, oil film has a greater effect, and that varies with temp and rpm.
These old Yamahas are robust engines, with only a few issues - valve seat wear, starter clutches and plasticcy chain tensioners is about it. The x engine, allong with similare age Kawasakis require the cams to be lifted to set valve shims... If you want to be on the safe side with clearances, just on or above max on the exhaust is a safe place to be, but the specs are your guide.

 

Yes, you got me