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