valve clearance question

For an 1982 XJ550:

I am checking the clearance for the valves (at room temp), following the original shop manual and the Clymer manual. They say to insert a feeler guage between the small side of the cam and the lifter after rotating the crankshaft properly (see Clymer fig 85)

My problem is that I cannot insert even the thinnest feeler (0.04 mm) between the majority of the valves and their respective cam. No matter how I rotate the crankshaft, I cannot insert my thinnest feeler.

Is this a Bad Thing? I am under the impression that there should be about 0.15 mm clearance according to specs. If it is a Bad Thing how could it become bad? I thought that the gap could only get bigger than 0.15mm?

Perhaps I am confused, I haven't done this before.

Thanks!

 

First off, as the valves wear, the clearances TIGHTEN because the valve pounds itself into its seat faster than the shims and cams wear. It's a bad thing in that too tight valves can cause a burnt valve if the valve never actually closes. You want to rotate the cams so that the lobe is sticking up at 90 degrees to the surface of the shim, so the lobes will be "tipped back" a bit on the exhaust side and "tipped forward" a bit on the intake side when positioned correctly. You're trying to measure the clearances between the "heel" of the cam and the shim. If your bike has some miles on it and the valves have never been checked, it's not inconceivable for a majority of them to be tight. I would go to Sears and try to find a set of feeler gauges with thinner sizes. If they're really at "zero" then shim appropriately and then re-check. You may need to redo a couple once you get thinner shims in and can measure the actual clearances. If the shim thickness calculation formula is confusing, write them all down (measured clearance and existing shim) and post and I'll give you the recommended shim sizes from the chart in the factory book. You will need to pop them out to see what size is in there to begin with, do not assume them to be all the same (even from the factory.) AND DON'T USE A MAGNET!!! I use a tiny screwdriver and hemostats.

 

Thanks for explaining that, bigfitz. I can't find a thinner feeler than 0.04mm, so I will assume zero-clearance. My bike has 25K miles.

I will need to pop out all the shims (one at a time) on the zero-clearance valves, and replace them with the thinnest shim I can buy from Chacal. Then measure, hoping the new gap will not be greater than my thickest feeler. Get those measurements back to you, then buy all the shims at once.

That should get'r done.

 

They should not be less than zero so you should be able to fairly closely calculate the needed shim. My Haynes shows down to zero clearance. You pull the shim - check it's number and look up the correct replacement. You can tweak that shim size to get to the middle or loose side of the spec - whichever you prefer.

 

Will add that if you get a valve that its valve lash is MORE than what is spec'ed out to, keep an eye or keep a log as to what valve moves which way.. It could be an extremely soft seat or a valve that is stretching beyond its spec. Valves getting closer is normal on the XJ's, however if you get a valve spec that is too loose then be wary of it since it might spit the valve head onto the piston and cause all heck to break loose in the combustion chamber.

Its happened to me once and a buddy on the grid of a race. Nothing like the feeling of the engine sucking a valve!!!!


Sean

 

Bill's right you shouldn't need to assume "the thinnest" you may just have to go down two sizes (or three) from what's in there. This may have never been done on your bike which is why they're so tight, but even from the factory you can't assume the shims were all the same. You'll need to look at the tight ones, and drop down shim sizes appropriately. Then simply recheck in case they WERE "less than zero" (which they should never really be.) Even adjusting away from "zero" will depend on what's in there now. Look on the bright side: Once you get this right the bike is going to run MUCH STRONGER trust me.

 

PM me with your email address and I'll send you a scan of the shim replacement chart from the factory 550 book. If you need cable routing diagrams or anything else just let me know.

 

I finally got the time and equipment to start the valve job. Here are the results.

Using a 0.02 mm feeler, with the fat part of the cam lobe pointing perpendicularly away from the valve shim top, I could not insert the feeler guage on any cylinders. I spent a lot of time double checking.

What do you think this means? My bike has 25K miles.

I proceeded to remove the shims and here are the results.

FRONT EXHAUST SIDE
Y275 Y275 Y270 Y270
Y260 Y270 Y275 Y270
BACK INTAKE SIDE

Do these look like the original shim sizes? Does it appear that my bike never had a valve job?

What shims should I replace them with? I would like to buy shims that are on the sides of the specs that will allow the longest life. I'm not sure how to accomplish that.

Thanks for the help!

 

To clarify, here are the measured clearances:

FRONT EXHAUST SIDE
0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00
REAR INTAKE SIDE

 

Original shims always vary, so those numbers will not do you much good... Get a thinner shim (210-215), and recheck each cylinder with it. That should put you back on the chart, so you can get the right ones all the way around.

It's better to set the valves on the loose side (but still within spec). You might hear a bit of valve ticking, but at least you know they're all closing.

A compression test and a follow-up clearance check soon afterwards (500 miles or so) wouldn't hurt, either.

 

Your description has me concerned. "with the fat part of the cam lobe pointing perpendicularly away from the valve shim top". I'm not sure exactly what you mean. Check out the valve clearance post by BIGFITZ52. he posted so great pics.

The lobes are egg shaped. Valves are closed when the thinner part is 180 degrees from the shim ( actually a bit sooner but this is where you want to measure) so the lobe "points " away from the shim

 

Wow!

Double-Wow!

I need a drink!



JT, something doesn't sound copa-setic. Although it certainly could be the case that you have zero-clearance in all your valves, that would be one of those "historical moments" that we're all so tired of hearing about by now...... :lol:

I don't know what the answer is, but I do know that I would check things again (even starting with the accuracy of the feeler gauge!) before you proceed any further..........

 

Hey Great Chacal,

I thought the same. All ZERO? I thought maybe because the temperature was cooler. I was surprised also.

To reiterate, I rotated the crank so that the "fat" and by "fat" I mean the part of the cam farthest from its axial center was pointing away from the valve. To expound, it would not make sense to measure it with feelers when the fat part is pushing down on the valve and opening it, of course it would be zero.

I checked with two separate feeler guages.

Maybe this would explain why starting it in the cold last year was such a long drawn out affair.

Do you think it would be a good idea to get a thin shim from you first just to get a better reading?

JT

 

If that is a 25K mile motor that has been run hard it IS entirely possible but I have to reiterate OWWW.

Look at my photo post, double check your methodology.

I would replace them each with a shim one or two sizes down and re-check. This is a 550? PM me with your snail-mail address and I'll mail you a whole boatload of used shims. You can use them to substitute for checking purposes (DO NOT RUN THEM, they are used) and send 'em back when you're done. That way you shouldn't have to buy any at least to figure out where you're at.

 

Cool, will do!

 

your going to have less clearance on a hot engine
a symptom of too little valve clearance is stalling at a red light after a long run at highway speeds
hard cold starting doesn't really fit with tight valves

 

if a person was to rotate the engine till the valve was fully opened, the cam surface opposite lobe could be wiped clean and covered with "magic marker"
then rotated till the valve was opened again to see if the marker is wiped off and it really has zero clearance

 

Weird, Surprised it would run at all when warm. The valves would have to just hang open and the engine would have no power and kill all the time when hot. I agree with Big Fitz. Put at least two sizes smaller shims in and recheck to get what you need on each valve. Bet it runs like a different bike when your done.

 

Polock, Thanks for the INFO!! I had that symptom (search xjbikes i swear)! I thought it was electrical or fuel, and that is what got me going in this direction. Stalling caused me to deem the bike UNRELIABLE.

MN, I am going to put in those shims and repost the readings. I am so hoping this bike behaves well, I've had days of pure XTC running it and want to see them again SOON!

Thanks mon

 

JT....yes, what Fitz suggested would be the best way to proceed.

 

Cool - I was not sure what you meant and since all at 0 is extremely odd I just wanted to be sure you had the right position to measure. Kind of the " is it plugged in question "

 

I don't know if zero clearance would be all that odd on a 550 with 25K miles if it never had a valve adjustment. On my '81, when I checked at 18K, there was one valve that was DAMN NEAR zero, and I know for a fact that bike had been done at least once in it's prior life.

When I did the '83 (the bike in the photo how-to) ALL the valves were tight, two were tight enough to require going down two shim sizes, and that was an untouched 7100 mile motor.

What IS odd is that it runs (ran?) at all acceptably.

 

Interesting. I don't have much history on my bike but with 42k on it I only had 2 at bottom of spec. I suppose someone did them along the line...

 

With 42K it would have had to have been or it wouldn't be running. Wait until he gets the 550 done and experiences the difference.

 

BigFitz sent me a few old shims (thanks!) and I used his Y250 and Y255 to get better readings. For posterity, here is the raw data:

Code:

KEY: a,b,c,d,e (e.g. Cyl 1 Front valve exhaust)
a = original shim, supplied for reference, e.g. Y275
b = BigFitz shim, e.g. Y250
c = thickest feeler that would fit (e.g. 0.30mm)
d = thinnest feeler that would not fit (e.g. 0.33mm)
e = needed shim, read from chart using BigFitz shim as "installed", need to obtain (e.g.Y260)

Cyl  Front valve(exhaust)            Rear valve(intake)
       a,b,c,d,e                             a,b,c,d,e
1     Y275,Y250,0.30,0.33,Y260    Y260,Y250,0.20,0.23,Y255
2     Y275,Y255,0.35,0.38,Y270    Y270,Y250,0.23,0.25,Y260
3     Y270,Y255,0.23,0.25,Y260    Y275,Y255,0.28,0.30,Y270
4     Y270,Y255,0.23,0.25,Y260    Y270,Y255,0.20,0.23,Y260

What do you think?

 

I think you may finally know what you need to order.

Where is Big's photo post of checking these?

 

http://xjbikes.com/Forums/viewtopic/t=14827.html

 

Is it a big no-no to reuse shims?

 

Yes. I believe chacal covers it in one of his tech articles, there are a bunch of reasons but the bottom line is you don't want to destroy your motor. Keep my used shims until you're done in case you miscalculated.

 

Chacal's in depth discussion is found in the thread called "Shim Pool?"

Another question about borderline measurements. Take for example Cyl 1 Front exhaust measurements above. With a Y250 in place, I measured a 0.30mm clearance and my next feeler was 0.33mm which did not fit. There for I am pretty sure that the clearance is a little more than 0.30mm.

The charts say to replace 0.26-0.30mm with Y260, and to replace 0.31-0.35mm with Y265. See how it is right on the borderline? Should I use Y260 or Y265?

This happens in a few other valves measurements and I was wondering about the tradeoffs and the margin of error, etc.

 

So what happenes when you run an engine for years, and you're down to the thinnest shims that keep the valve train in spec? Does that mean that the valve seats, and hence the cylinder head is toast and you need to get a new one?

 

Should I use Y260 or Y265 on Cyl 1 Exhaust valve?

 

I say go for the largest, safe gap so that you have the longest time between shim changes.

 

Thanks, I am good to go now.

 

Not gonna happen.
We're running mostly between 240's and 270's now; they go all the way down to 200. If that DID happen, then the answer would be yes, time for a new head and valves.
It's my understanding that the longer you run these motors the less the valves need adjusting. I plan to find out.

 

I purchased a gasket for the valve cover, what is the best brand name of adhesive to get that is easy to find? Thanks!

 

I use Permatex high-tack spray gasket sealer.

For the valve cover, I spray some into a cup and use an old artist's brush to paint it into the groove. Once the stuff has had about 10-15 minutes to "dry" it is the STICKIEST stuff on the planet. Once you've stuck the gasket to the cover, let it set up for an hour or so. Then smear the other side of the gasket with silicone lube or gear oil or even vaseline.

You beat me to it; I'm gonna add this part to the "how to" but I don't have the valve cover done yet.

 

Well, there's still time for me to use it I won't be putting in the shims I ordered until the next warm Texas day in the 70's.

BTW Big, do you know of a photo how-to for synching carbs? Or adjusting the idle mixture? Your howto's are indispensible.

 

I just purchased an ’82 (i'm a retard) 650. I have spent HOURS on this site. I am currently rebuilding the carbs, thanks to all of you. Thanks to everyone!!! I am going to do my valves BEFORE I even try to adjust the carbs!!!

 

I'm still a noob, but can get you going with what I did, just ask, T-man.

JT

 

By the way, if there is anybody in the Austin TX area that can rent/loan me their home manometer for syncing carbs, that would be great. I'm just a poor boy from a poor family and not in the position to buy the tool yet. I might have to break down and build one.

 

Ok checked the valves.
Here are the results.
I used the zip tie method, worked perfect.
Does this look correct?
Here is my question. I can flip flop shims on a few and need (5) Y270’s. I have read chacal’s reasons not to reuse shims and read several other people saying they have reused shims. I am unsure of what to do.
Does any have a link to the shim pool or have (5) 270’s to exchange for (3) 275’s (1) 285 (1)290?
Sorry the only way i could attach the excel sheet is this way, I tried it several other ways and it did not work. Any ideas?

 

I do not recommend reusing shims either. chacal carries aftermarket shims for less than half of OEM. I only keep my used shims for testin/measuring purposes.

 

Tman_74, only problem I see on your spreadsheet is the intake valve spec . Your showing .16 - .20mm. Should be .11 - .15mm for an 81-650 I believe.
On the Intake, asumming L-R = 1-4. #1-ok, #2 needs 2.75, #3 needs 2.75, #4-ok.

On the Exhaust, same L-R = 1-4. #1-ok, #2 is that a tight or loose .152? If loose-ok, if tight I'd go with a 2.70, #3 needs 2.75, #4 is that a tight or loose .152? If loose-ok, if tight I'd go with a 2.70.

 

I am a retard, I was told the bike was an '81, the bill of sale says '81, the frame says '81, but the title says '82 and it is a ycis motor, so it is an '82. Sorry rpgoerlich, now how does it look??? They were all on the tight side..

 

The XJ650 had the same clearance specs all years, YICS or not.

 

I just finished my valve gapping job. It is a difference of night and day!!! The bike just fired up, even without synching the carbs yet!! So worth the time and effort. THANK YOU to all who pointed me in the right direction.

JT

 

Hey guys, i hope this post is still being scanned by xj gurus. I checked my shims and their clearances yesterday. There were three that I couldn't stick my .004 feeler into, so I'm going to get a new shim based on just a little thinner than that (good idea, yes?)

my REAL problem is that on one of those, I absolutely COULD NOT get the shim out of the bucket to check its number. I pried it up as much as I could with a little (nonmagnetic) screwdriver, and tried to pry it out as I did with the other shims (also with non-magnetic stuff) but i absolutely COULD NOT get it out! I stuck one side of needle-nose pliars in to pry it out and as i lifted it, the bucket went down--even with the tool holding the bucket down obviously not far enough). I seriously tried this 7 times (replacing the tool, prying it up, etc...) I don't know what to do about that.

Any ideas on how to get that blasted shim out??


and one other question, I pulled this shim out, and have no idea what the number is. I was hoping a more conditioned set of eyes could interpret it for me.

 

that's actually upside-down. here's a rotated image of it.

 

sorry, here it is.