VALVES FIRST or your carb efforts will fail!

VALVES. Nobody wants to hear it but here's the deal:

The intial valve clearance check, the most important, was to have been done at 3000 miles. For a lot of these bikes, they were well out of their short warranty by then. So in most cases, and since the bike was running fine, it was ignored.

Next valve clearance check after the initial 3000 miler, was to have been done 5000 miles later (at 8K.) Five thou is the maintenance interval for valve clearances. By the time the bike had 8000 miles on it, it was probably on its second or third owner; and unless one of them knew what they were doing, it was ignored, again.

THEN YOU BOUGHT IT.

You CANNOT, repeat cannot get a decent vacuum sync on a 4-cylinder, CV carb-equipped bike if the blasted valve clearances are not in spec. Just ain't gonna happen. WORSE if some of those valves are approaching "so tight they don't close fully." Also known as Burnt Valve City.

So Fitz, how do I know if my newly-acquired (or maybe you've had it a season or two) sweet-running XJ NEEDS a valve adjustment?

Have you done it since you owned the bike?

Do you have hard proof (receipts, etc., ) that it was EVER done?

Take the odo mileage. Subtract 8000 miles. That's how overdue you are if the initial check was ever done.

Take the odo mileage. Subtract 3000 miles. That's how overdue you are IF THEY WERE COMPLETELY IGNORED.

Save your motor (or at least your exhaust valves.)

Check your valve clearances; and be sure they're IN SPEC before attempting to sync your carbs or you won't be able to; honest.

Simply ignoring, denying, or looking past overlooked valves is a recipe for a burnt valve.

End of rant. I was getting tired of typing the same thing over and over.

FROM THE FACTORY BOOK(S)

 

Thanks Fitz!
Here I go enroute to the corner starin' at my feet... :lol:
I'm sittin' on 7K and would bet good money they haven't
been touched. Got it set up for this weekend, Hell or
high water. Too ironic... It was 104 on the way home
from work this afternoon and the hair was standin' up
on the back of my neck..! All I could hear was Fitz cleanin'
my plow! :wink: Yes sir, I'm goin' to get my arse back
to the startin' line and get this poor thing lined out.

Can ya' imagine havin' to get on here and...
"Well ladies 'n gents, I just melted my XJ!" Shoot,
I believe I'd sign outta here first. Thanks for all the
GREAT advice and wealth of knowledge!!! Consider
it done. I can't take this feelin' all yucky anymore... :lol:

 

Fitz, I applaud you for your dedication to this topic. I think it should be made a sticky along with a link to your write up on how to do it.

That being said, I disagree that there is a direct correlation between getting a good synch and valves.

I do agree that valves should be done, period. And for that reason, it should be a sticky.

So I need to heed my own advice.

 

Fitz is correct, if your valves are to tight they will not close completly, thus making a carb sync impossible. Remember as our valves wear in the clearence gets closer possibly keeping the valves open.Valve clearences are a often neglected part of maintenance, either by us or the PO.
Listen to the advice of the experts, their wisdom is also often ignored.

 

Makes sense to me! I was going to leave the valves until after I had done a few other things on my bike but after reading Fitz's follow-up I Think I am going to get into those valves before trying to start the engine for the first time. My rule of thumb is that being causious is a sign of wisdom when it comes to motorcycles rather than a sign of old age like some think. grunt007, 81'XJ750 Seca R, Mi.

 

The valves control when and how much mixture goes into the cylinder and when and how much exhaust gets out. The valve clearances affect valve "timing" (a tight valve opens sooner and closes later than it should.)

Those variations greatly affect manifold vacuum.

Manifold vacuum is what you "read" when you're doing a sync.

You're deluding yourself if you believe that changes in manifold vacuum won't affect tuning vacuum-operated carbs. Remember, you're not actually synchronizing the carbs; you're using the carbs to sync the cylinders' vacuum signal which is impossible if a valve or two is way out of whack or not closing all the way.

That is why the factory book clearly states that the valve clearances need to be in spec BEFORE trying to sync the carbs. Quote:

"NOTE: The valve clearances must be set properly before synchronizing the carburetors."

The main reason that so many of these bikes are in need of a valve adjustment is the perceived difficulty along with the false security of "the bike's running fine, why should I touch it?"

Why? Because if you don't, you're going to eventually burn a valve. And be horribly frustrated trying to sync your carbs.

Hence the title of this thread. I've done everything I can do to make the process as easy as possible; yet people continue to go through all SORTS of interesting rationalizations as to why it's not necessary, all the while cursing their carbs.

Ya just gotta do it. You can't fight physics with denial.

 

I was one of those people who thought it was really difficult.... and it's not... it took a while for the first 4.... I flew through the last 4. (Used zip tie method not shim tool) Definitely recommend a metric deeper gauge... not one with metric equivalents....

 

Three cheers for Bigfitz! His valve adjust post + pictures is worth it's weight in gold. (double down, Bigfitz, for showing us how do-able it is). If your valve clearances are out of spec, and you properly adjust, the performance of your bike will immediately, and obviously, improve.

Mlew said that out of spec valves will not close completely. Not true. Carbon deposits or wear will keep them from closing completely, but properly ground valves are closed virtually all the time. Their natural state is closed.
Look at the Bigfitz pictures. The clearance, when there is at least SOME SPACE between the cam lobe and the shim/valve, is measured at the fat end of the egg-shaped lobe. When the pointed end, the long end, of the lobe is down against the shim it is pushing against it, and this opens, not closes, the valve. As the pointy end goes past the shim, the spring-loaded valve stem is able to move back up against the cam lobe, and the valve down below snaps shut. At say 7200 rpm (divided by 2, because 2 of the 4 cylinders are synched) means this opening and closing of the valves is occurring 6 times a second.

So what's happening when your valves are too tight? It means that as the pointed end of the cam lobe approaches the shim it starts to push against the shim, and consequently push open the valve, too early. And then, when the pointy end tries to move past the shim, it stays in contact too long, and the valve down below remains open too long. So the problem is too much open, not too much closed.

You can draw your own picture of the intake/compression/power/exhaust strokes of our 4-stroke engines. For intance, bad valve clearances could mean that on intake stroke, an open intake is trying to suck gas/air into a chamber while simultaneously sucking spent fuel from a late closing exhaust. Each intake and exhaust stroke presents energy sucking, power defeating combos. Every cylinder, even the synched ones that have different clearances, are trying to do something different. So you can solve a lot of probelms with one fix.

When deposits or warping prevent valve closing you are going to have compression and power stroke losses. Then you need a valve grind not a valve adjust. But you should be doing something like 12-20 valve clearance adjustments before you need a valve grind. And even dirty or warped valves are going to function noticeably better if the clearances are in spec.

 

Tight valves will get tighter when hot. I have seen engines with almost zero clearance cold that when hot have a missfire due to the valves staying off the seat. Last time it was on a Toyota Landcruiser DOHC engine that had valve recession due to LPG use.

It does happen.

 

No short cuts!

These bikes will run like new if you listen to the guru's and do it
right.

My bike ran like crap at first (prob one reason the po was selling it).

I lurked on the site for months learning all I could, then went step-by-step
as fitz and the rest advised and lo and behold I soon had a great little machine that is still smoking a lot of bigger bikes less well tuned.

I can't thank our experts enough for that.

Just my 2 cents.

 

Hmm. My '82 Seca 650 is reading around 57000 miles (yes, three zeros). Sounds like I'd better look at the valves...

 

Today i checked the valves and my feeler gauge is metric and it has .10, .08, .07..etc.... When i checked my exhaust and inlets were all .08... Can it really be that far off from what Ive read... exhaust at .16-.20mm and inlet .11-.15mm... Or does my gauge not read in small enough increments

 

It's definitely easier to change shims than to rebuild an engine. Thanks Fitz!!! I had 2 exhaust touching and the others were really close to touching and my intakes were all too far. Now they are all factory spec.

 

I've been looking for two days now for the guide on how to check valve clearances (I found the adjustment guide - wait are they the same?). Can someone post the link to end my wandering in the desert?

I had the carbs cleaned and synched, but it looks like valves weren't checked. I'm hoping to be able to at least check the clearances before having to take it to the shop. I've got feeler gauges and a few tools, but only an alley to work in. Do I need to pull tear the gas tank off and open up the engine to check the valves?

Thanks

 

You do need to remove the gas tank and take the valve cover off to check the clearances. The job is much easier if you have a true metric feeler gauge.

This is the basic "how to" on aircooled XJ valve clearances; although I did the article using a 550, all of the aircooled XJs are the same under the valve cover: http://xjbikes.com/Forums/viewtopic/t=14827.html

This is the addendum to the first article; which explains the issues encountered with the use of the "shim tool" and a popular alternative to its use: http://xjbikes.com/Forums/viewtopic/t=29209.html

 

Thanks Fitz,

I think I might be able to do that much. Related issue, I've been having some oil seep out on longer rides when I start goosing it over 6-7k rpm. It looks to me like it might be seeping out of the valve cover gasket. Is that a likely source of an oil leak? I'm guessing if there is a problem with the gasket and I need to replace it that I might also need to replace any washers/donuts?

Cheers

 

Yes, yes and yes. On a YICS motor, the "donuts" are what actually push the valve cover against the gasket/head, because the bolts have collars that limit how far they can be tightened. Quite often even a new gasket will leak if the donuts haven't been replaced.

 

More thread-bumpage.

If you're having "carb" troubles but haven't checked your valve clearances yet, go back and read through this thread.

I'm getting tired of typing.

 

Fitz, I was talking to a guy at work a real biker ridden most of his life and has always owned Kawasaki bikes, when I was asking his advice about an issue and asked him about getting some help with my carbs when I go to do them later this fall. He was pretty adimate that you could do
The carbs without doing the valves first and without a YICS tool. I told him that is not was suggested by everyone on this site or the original and after market service manuals. Maybe, this type of thinking and not realizing these motors are radically different for other bikes is part of the issue

 

Rick, you know that and I know that; I adjust my valves (and usually find at least one is too tight for spec) every 5K miles. As, I'm sure, do you and every other XJ owner who actually rides his bike and plans to keep doing so for a while.

What absolutely amazes me is the lengths people will go to, the rationalizing, second opinions, old wives' tales, etc., to talk themselves out of it.

Just gotta do it. Notice #6? Want to get started on that one?

 

Oh believe I am in the church. After I get my new shims installed I will at 5K do it all over again. The carbs will have to wait a bit longer though I will need help with those. I have a new fuel line, and I've inspected the vacum line as much as I've had that gas tank off in the last few weeks...

 

"Sync the carbs? Oh it runs fine now, no need."

"The previous owner said the previous owner synced them."

"Mr. Motorcycle Expert down the street said syncing too frequently could damage the engine, and that I should bring it down for him to do it."

"But my spark plugs are all the same color."

"It takes too much time."

"Oh but I bench synced them, it's okay."





Did I miss any?

 

This is going to be a very dumb question but here it goes keep in mind I am a noob....

Why is synching so important? What causes them to get out of synch? And what are the consequences of running with carbs out of synch?

 

It's important because of the consequences of running with them out of sync. We don't want those 4 cylinders "fighting" each other, we want them all pulling together as a team.

They get out of sync because it's not actually the carbs you sync, it's the cylinders. As the valves wear, the valve clearances change (decrease) but not all at a uniform rate. As they change enough, the cylinders get out of sync with each other; the bike develops a hanging idle, becomes difficult to start, runs rough/vibrates excessively and your fuel economy goes away.

So, you get the valves in spec. OK, now they're in spec, but they're NOT all running exactly the same clearances they were when the carbs were last adjusted.

So we need to go back and fine-tune the sychronization of the carbs in order to synchronize the output of the cylinders as best we can by adjusting the carbs.

If shims came in .01mm increments instead of .05mm and we could (theoretically) "match" the cylinders a lot more accurately by getting the valves all shimmed the same then the carbs wouldn't need to be sync'ed to adjust the outputs. As much. They'd still need to be in sync, re-adjustments wouldn't be needed (theoretically.)

Bottom line: Running out-of-sync is hard on the motor; on the rest of the bike from the increased vibration levels; and on the rider (from the impact on his wallet.)

 

Fitz, this topic is NEVER going to end for you is it?

Bless you for your knowledge, patience and perseverance.

Loren

 

Thanks.

It seems like every noob that comes along has a 10K~25K mile bike that's hard to start when warm, won't idle, etc., and will do anything to avoid the obvious. Or even argue about why it's not really necessary.

I think it's "used car syndrome."

I just get tired of typing the same thing over and over, so I bumped these threads. One of my own first "rude lessons" in motorycle mechanics was a burnt valve. I hope to avoid others having to learn the hard way, but it seems to be an uphill battle.

I could always stop. Except that would probably result in a few dozen freshly-cooked XJ motors in short order, and we don't want that.

Maybe I should buy a Beemer.

 

Well Bigfitz, I for one appreciate your knowledge, patience and perseverance. So keep on keeping on.... Some of us are listening...

 

Like most things if someone does not want to do something, they come up with all sorts of reasons as to why they shouldn't. Simply the attitude is if it's running why should I set it up right thats too much effort and I just want to ride. Result Buddy comes on forum wants to know why bike runs like sh#t and wants problem resolved with no expense or effort on his part. I'm not exaggerating I don't know how many threads I have read on here that follow that exact attitude.
People want advice but don't like to hear that they have to make an effort to get there machines running the way they are meant to. One thing I have learned is if something is out of your area of expertise, LISTEN to those members on here who do know what they are doing!!!!! I'm sure they would rather be out riding or working on there bikes then beating there heads against the wall trying to keep people from making some of the same mistakes they made when they where noobs.
Listen, learn , head the advice of the experienced and what would have taken months can be accomplished in hours.

 

You Ground-Hugger are 100% correct!

 

The "Number-6" Sync requirement.

The Initial 3,000 Mile "Requirement" brought the Bike back to the Dealer for a Multi-point Inspection and "Sync-check". The visit generally smoothed-out any rough-running new Bikes and let the Dealerships make needed adjustments and suggestively sell parts, accessories and maintenance packages.

As for the 2,500 Mi / 6-Mo. Sync--Check.
That might be more frequently than absolutely necessary.
The recommendation supposes that each Bike sold was to be brought to a Dealer for its servicing.
After-sale revenue-generating service to keep talented technicians busy doing profitable scheduled maintenance and owners filling-out the Dealership's Customer Satisfaction surveys favorably.

 

Equine Plumage. It wasn't covert revenue generation;

It was primarily to ensure the bikes stayed within EPA specs. It is listed under "emission controls maintenance" after all. By performing a carb sync (and Yamaha assumed it was being hooked up to the EGA for this; you and I know differently) between valve adjustments, they were ensuring the carbs stayed "on top of" the changes in the valve train, enmissions-wise.

You really only need to re-sync after you re-shim a valve, which causes a major shift in the vacuum signal from that cylinder (relatively speaking.)

Ultimately, you're correct. The 2500-mile re-sync is a bit uneccessary (although optimum fuel economy would mbe maintained as well) but it should be done every 5K when the valves are.

 

Man, oh man.

Time to bump this puppy again; we've got a couple or three members who're still beating their heads against the wall trying to tune their carbs before getting the blasted valves in spec.

Looks like at least one may have finally wrapped his head around it; but some folks just won't accept the fact that it's a necessary part of maintaining an XJ and getting (and keeping it) properly tuned. It never ceases to amaze me the lengths to which people will go to convince themselves it's not necessary or "everything's fine" when they don't have any idea if it is or not. You can't "deny" it away! Check the bloody clearances already.

So, go back and read the whole thread; OR, just look in a FACTORY BOOK:



Note the words "MUST" and "BEFORE" I don't know how to make it any clearer.

 

I just found this from direct experience out last week. Bike was synced up and running fine six months ago (i'd done EVERYTHING on it the year before). Did valve inspection and found that the #3 intake was JUST BARELY LOOSE. I always had trouble fattening up the mixture on #3. Ordered the shim.

Crashed the bike. Finally getting it back on the road and installed the shims. Everything was in spec, and kept getting a hanging idle around 1500-2000 RPM that I couldn't get to settle down. Started freaking out thinking it could be ANYTHING, but soon realizing that I MUST resync after that change. Will do today, and hopefully I'll have a BIG grin on my face for the rest of the weekend!

 

I don't think we should state that the effect on TIMING caused by Valves which are a few thousandths Tight or Loose is going to have a MASSIVE effect on Performance.

When you have an Engine that has Solid-type Lifters, ... you must be conscientious about maintaining the Valve Clearances because a TIGHT Valve on a Air Cooled Bike left undetected WILL have an effect on Vacuum.

You risk having that Valve get BURNED.

And, ... THAT ... really sucks!

 

I just checked the compression on the 1100 BEFORE putting the valves in spec', lets see how much difference it makes......
Results posted in Project 1100 thread.

 

Fitz, how does one use a feeler gauge on the valve clearances if the valve cover is still on? In your article, you take the valve cover off and check them thoroughly. I would still like to check them the right way and will probably take off my valve cover, but how does one do that without taking it off?

 

You can't. You DO need to remove the fuel tank AND remove the valve cover to check the clearances. Did you mis-read the above?

You'll need to remove not only the fuel tank and the valve cover, but also the LH timing cover as illustrated in the article. You will probably also need to slide a relay or two off its mounting tab to gain clearance for popping the valve cover.

 

OOPS! Yes I did misread that!

I recently cleaned, re-jetted, and rebuilt my carbs. Next step is to check valve shim clearances, then sync (using a vacuum gauge?), then colortune.

Is that all correct?

 

Pretty much; as long as you wet-set the float levels, and do a good precise bench sync before the carbs go back on.

 

What is wet-setting the floats? And are you saying that I need to sync the carbs before I put them on? Would I do that by assuring that the idle adjustment screws are all equally turned?

 

Wet-setting the floats involves using fuel and a piece of clear tubing attached to each carb bowl drain in turn, and ensuring that the float levels are within their 3mm adjustment "window." Using this method allows you to "see" what's going on inside the float bowl, and at exactly what level the floats are actually shutting off flow. This is a critical adjustment.

The process is covered many times on the site, including Schmuckaholic's collection of PDF writeups. Look in "XJ FAQ Suggestions."

Yes, there is a basic synchronization that is done first:

The idle MIXTURE screws should all be set at about 2 1/2~2 3/4 turns out.

"Bench sync" refers to the mechanical synchronization of the individual throttle shafts/butterflies so that they all open and close as equally as possible. This is accomplished via the three screws on the throttle linkage along with the main idle knob.

The running vacuum sync completes the synchronization process.

 

I began to bench sync my carbs, first by making a starting point. So I turned all four screws in as far as possible to see where the furthest point in is with the screws. But I ran into a problem, my mixture screws stop at different points. The outer two are close to each other but the inner two are on a different page, yet close to each other also. Is this a problem or is this normal?

 

do you mean bench-sync screws or the little pilot mixture screws?

**EDIT** nevermind if you turned four screws then its gotta be the little pilot mixture screws. these don't matter what position they are when turned all the way in. most of us start with them turned out 2.5~2.75 turns.

but either way, this is one of the last steps. make sure the bench-sync with the three sync screws turning the butterflies is as close to good as possible. (what fitz was describing) it will make the last steps easy for fine-tuning

 

Oh, that makes more sense. So does it even matter that my pilots all start at different places?

And is there a way to be exact with the butterfly valve bench syncing?

 

By "all start at different places" do you mean that the screw slots all end up in different positions when the screws are fully (gently) seated?

If so, that's not a concern.

The best way to get a good accurate bench sync is to use THIN strips of business card or narrow strips cut lengthwise from a 2-liter plastic beverage bottle (since they'll have a little curve to them.)

 

Ok, thanks. You have been a great help.

 

>>>what I said<<<

Start at page 1 and read the whole thread. It really is too much to keep typing over and over.

 

(I wasn't referring to you, DS.)

 

Hey Bigfitz52, Didn't you forget something like the thread for going through the carbs? grunt007, 81XJ750 Seca R, Mi.