Cam chain slack

Adam Fraser · September 20, 2003, 11:20:29 AM

In general, how much slack should you have in your cam chain with the valve cover off. I know this is far from scientific, but at least it would give me a baseline to go by. Just figured I'd check while checking vlave clearances.

KevinC · September 20, 2003, 11:55:11 AM

The cam chain should be pretty tight. Maybe 1/4" up and down movement between the cams.

If it musch slacker than that, the cam chain tensioner isn't working properly. You can compensate temporarily by manually tightening it. If you stick a small straight screw driver in the opening at the back of the cam chain tensioner (it has a rubber plug if it hasn't been lost), you can turn it in (clockwise) to snug up the chain. How much is a good question!

Adam Fraser · September 20, 2003, 01:34:20 PM

When I first pulled off the valve cover there was quite a bit of slack, but when I turned the engine over once, all slack was gone and stayed gone. Is this normal for the GS? Thanks

KevinC · September 20, 2003, 01:48:54 PM

Nope, that's not normal. If you continue to turn the engine over through 2 revs, does the slack re-appear at any point? The cam loading can make the top run of the chain tight sometimes, and drive the slack elsewhere.

The cam chain tensioner is a spring loaded ratchet that only tightens the chain. It isn't supposed to be able to back off, but sometimes they stop working properly.

I made a mistake above - you turn the cam tensioner counterclockwise to tighten the chain. clockwise will retract the tensioner.

Blueknyt · September 20, 2003, 09:50:35 PM

i prefer manual tensioners, got couple from GS450, that im gonna rework for that reason.

Adam Fraser · September 20, 2003, 10:52:53 PM

Cam chain tensioner is shot. Spring was broke and out of shape. Just hope no damage was done in finding this out. Maybe made one or two revolutions with starter without cam chain tension. Now I guess I'll have to buy a new tensioner. Thanks for the suggestions

KevinC · September 21, 2003, 08:28:06 AM

Check the cam timing once you get a tensioner in it. There is a good chance that the cam chain will have jumped a tooth or six on the exhaust cam.

The safest way to do it would be to remove the cams, and start from scratch with the cam timing. If the chain has jumped, turning over the engine can easily bend a valve. I've done that myself, and it is very easy to do.

sprint_9 · September 21, 2003, 09:02:33 AM

So what would be signs of a junk cam chain tensioner if you dont take the valve cover off? How do you put one on, do you just bolt it on?

Adam Fraser · September 21, 2003, 09:23:57 AM

Pulled the valve cover off, definitely jumped a tooth-or 6

Now, how do I check for a bent valve while doing this job, so I dont have to do it again. Kevinc you have been a great help, thanks.

KevinC · September 21, 2003, 09:39:30 AM

OK, if it has jumped teeth, you definitely want to pull the cams before moving the engine any more.

It is a bit difficult to check the valves with the head on. There are a few things you can do. Easiest is to re-time the cams, and then check the compression after. If you don't have a compression gauge, even just putting your thumb over the spark plug hole and cranking it a few times will give you a good idea. If the compression is good, you will feel it, and it may force your thumb off the hole.

You will want to have the spark plugs in the boots, and grounded somewhere, so the spark has somewhere to go. Some electronic ignitions don't like firing with no spark outlet. Not sure about the GS one, but no sense taking the chance.

The other head-in-place valve check methods would be to pull the exhaust and carbs. Shine a bright, small, light in the spark plug hole, and see if there is any light in the exhaust or intake ports. Works best in the dark. Or you can use an eye dropper or something to put a low viscosity fluid in in the cavity around the valves, and see if the valves are leaking. Gasoline works well, but be careful.

I think Bob Brousard's cam timing method is up on Pantablo's site, or I can re-post it. It works very well, and is pretty fool-proof.

KevinC · September 21, 2003, 09:49:12 AM

Quote from: sprint_9So what would be signs of a junk cam chain tensioner if you dont take the valve cover off? How do you put one on, do you just bolt it on?

They just have two bolts, and are very easy to take off and put on, although the carbs are in the way if you don't disassemble anything.

I think the easiest way to check the tensioner would be try winding it into it's retracted position, and see if the spring is working properly. at the very back of the tensioer, there is a small hole, sometimes with a rubber plug in it. Take the plug out. Put a small straight screwdriver in the hole, engage the slot, and start to turn clockwise.

You should be able to feel the spring tension immediately. If it is weak, or there is none, you have a problem. If there is good spring tension, just release it. It will adjsut itself.

If the spring in the tensioner breaks, then the cam chain will just keep getting looser. I would think it would start to run poorly, and make slapping and chain noises. Worst case it starts to jump teeth on the cam sprockets, and then things will get bad in a hurry.

Adam Fraser · September 21, 2003, 10:22:25 AM

Since I have to do it anyway, is pulling the cams right now before I get the new tensioner a good idea?

Edit: I read the cam timing info, kinda answered my question. Guess I'll just have to wait until the new tensioner comes now, if someone has one let me know, otherwise its off to the dealership Monday or Tuesday to get one.

Adam Fraser · September 21, 2003, 11:33:15 PM

Well, since I was already this far, I just took off the head and cylinder because the base gasket needed replacing anyway and to check the valves well. Everything looked really good, no bent valves that I can see, I assume there would be some kind of witness marks on the valves if they contacted the piston and they look to be firmly seated in the head. The base of the cylinder for some reason had dirt around the two studs that are at the center of the engine which I thought the gasket would have stopped. Anything else I should check while it is apart? (it'll likely be that way for at least a week).
What a 1 hour valve check this turned out to be, but oh well, it'll be my first 4 stroke top end experience besides a few single cam quads.

KevinC · September 22, 2003, 07:24:18 AM

The best way to check the valves is to invert the head and put a low viscosity liquid in the combustion chambers to see if it leaks down. Gasoline is the standard test fluid, but be careful. When I bent mine, the two valves had just touched, and there wasn't any visible marks on them.

The dirt around the studs is normal. Those studs are open to the world, and collect everything.

The Buddha · September 22, 2003, 07:30:37 AM

Well might as well replace the seals (Suzuki valve seals were pretty pathetic even when new) and hone the barrels and hand fit some new rings since 99% of the work is done by pulling these apart.
Cool.
Srinath.

Adam Fraser · September 23, 2003, 02:52:50 PM

Fillled combustion chambers with gas, no leaks. Now just have to waint for the dealer to get the gaskets for me (head, base, head o-rings). Again, if anyone has a Cam chain tensioner email me at fraseradam@hotmail.com

Once the gaskets come in I'm sure I'll have 100 more questions.

BTW: what are the torque specs for the head and the tightening pattern?

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Cam chain slack