Embarrassing Noob Question - What and Why Valve Check?

[Raydr]

Alright, so I've had my bike for a year, and put about 7000 miles on it. It is my primary transport to/from work and around town, so I try to be as nice to my baby as possible.

It's winter time and, like last year, the bike is acting up just a little. I'm purchasing extra things I need to take care of her during the winter - just got a battery tender that puts an end to my having to bump start the last 2 weeks (my ride to work is less than a mile, so it's not enough time or RPMs to charge the battery).

My experience so far: installing progressive springs, rebuilding the carbs (remember this?), replacing the tires, 15T sprocket and other minor stuff.


Anyway, I've decided that I need to do a valve check/adjustment. Except - I don't even understand what the valves are/do?

I'm searching for the elusive "Kerry Burton Valve Adjustment Video" and will go through my manual later to see what I can find out. (The Valve Adjustment page on this site is not newb friendly and assumes you know what everything is on the bike...)

But for now, here's what I've learned from reading the forum posts:

1.) It's easier with special tools and if you remove the carbs, but I can do the job by just removing the tank and that will give me access to what I need, and I'll be able to do it with my standard tools.
2.) Apparently I need "shims" ahead of time - I'm not exactly sure what these are or where I can get them. Or what the purpose is.

Unfortunately I don't know anyone here in Miami who can help with this one - and I'm not about to pay a stealership for something that I can do myself in a weekend - and learn something from.

So...any thoughts for this clueless guy?

Thanks in advance.

[beRto]

Anyway, I've decided that I need to do a valve check/adjustment. Except - I don't even understand what the valves are/do?

Valves control "air" flows in and out of the cylinder. Intake valves open at the right time to allow fuel/air into the cylinder. Similarly, exhaust valves open after combustion to allow exhaust gases to escape.

Valves "timing" (opening and closing at the right times) is controlled by the camshaft. This is a shaft that contains several tear-drop shaped lobes ("cams"). Depending on the position of the camshaft, the cams push open the valves. Because the engine components are moving very fast and subjected to high temperatures etc., it is important that the spacing between the cams and the valves be quite precise. This spacing is what you are checking and adjusting when you "adjust the valves"

1.) It's easier with special tools and if you remove the carbs, but I can do the job by just removing the tank and that will give me access to what I need, and I'll be able to do it with my standard tools.

I don't think you need to remove the carbs. You will need to take off the fuel tank. You will need a special tool to remove the valve shims (search for Motion Pro valve tool, it's about $30) - I wouldn't waste your time doing this job without the tool.

2.) Apparently I need "shims" ahead of time - I'm not exactly sure what these are or where I can get them. Or what the purpose is.

The space between the cam and the follower is controlled by a shim positioned in between them (see figure).



From this picture, you should see that a thicker shim would create a smaller gap, while a thinner shim leaves a bigger gap. Therefore, by changing the shims, you can create almost any gap size you need (i.e. adjust the gap to be within Suzuki specs).

You don't need shims ahead of time. First you have to measure the gap. If the gap is too big or too small, you will have to replace the shim. You look at the size of the old shim (it is stamped on the side) and buy a bigger or smaller one that will provide the gap that you require. You can get them at most dealerships or motorcycle shops (about $5 each).

I'm not about to pay a stealership for something that I can do myself in a weekend - and learn something from.

I encourage you to do this yourself; you'll learn a lot about the bike that way!

[GeeP]

Berto has it covered.  (Nice illustration BTW)

The reason for checking the valves on a regular basis has to do with wear.  Over time, the hard valve wears into the softer valve seat.  This causes the clearance between the camshaft and shim to decrease.  Eventually the gap will decrease to zero.  If the clearance isn't adjusted by this time the cam will begin to hold the valve open, causing blowby.

Blowby is when hot exhaust gasses pass between the partially open valve and seat.  The engine will begin to lose power and may "pop and spit".  If the engine is left in service the valves will ultimately torch as the small amount of unreacted oxygen left in the cylinders after combustion burns away the margin of the valve as below:



I definately encourage you to do it yourself.  The GS is an easy engine to work on and will give you the confidence to tackle larger, more complicated projects.  Get a Clymer's manual for your bike and a good basic set of metric tools from Craftsman or similar.

Kerry's excellent video can be found on Google Video by following this link:

http://video.google.com/videoplay?docid=-2015554469142545363&q=kerry+valve+adjustment&total=1&start=0&num=10&so=0&type=search&plindex=0

[gsJack]

Read this first so you know how an internal combustion engine works:

http://auto.howstuffworks.com/engine1.htm

You put 7000 miles on the bike, is that the total milage on it?  On my 97 GS I checked the valves at 600 miles and about every 8000 miles after that.  Never had to change a shim till about 40k miles on bike.  Did about the same with the 02 GS I bought used.  I kept a record of my valve checks:

http://img.photobucket.com/albums/v443/jcp8832/valveclearances.jpg

No need to pull carbs, just pull the tank and valve cover and check them.  Not that hard to do, I've buttoned it up and used it then till I got some shims and changed them later if needed.  Changed quite a few shims without the valve tool, just need a couple screwdrivers to change shims.

http://img.photobucket.com/albums/v443/jcp8832/ValveShimTools.jpg

[Kerry]

To go along with the other great replies, I just now updated [THIS OLD POST] for your benefit.  I replaced a paragraph that contained broken links with some new text and a new link.

It's kinda long ... you may want to print it out (unless you have a dual-monitor setup) so you can follow along with the animations and other links.

PS - Geep's photo shows a 4-valve-per-cylinder arrangement.  Our GS500 engine only has 2 valves per cylinder.  (Wouldn't want you to get even more confused after reading that mega post of mine!  )

[GeeP]

PS - Geep's photo shows a 4-valve-per-cylinder arrangement.  Our GS500 engine only has 2 valves per cylinder.  (Wouldn't want you to get even more confused after reading that mega post of mine!  )

Good point!  Yes, the photo is not of a GS engine, but a BMW M52 (car) engine.  I just wanted to show the torched valve in the upper right corner.

[Kerry]

Good point!  Yes, the photo is not of a GS engine, but a BMW M52 (car) engine.  I just wanted to show the torched valve in the upper right corner.

Yep ... and a good (and sobering) illustration it is, too!   

[Raydr]

Thank you everyone - great great responses and now I understand!

I guess my only question now is: where do I get shims? Are the Home Depot type items or something I'd want to order from BikeBandit?

Thank you!!!

[Kasumi]

No you wana be looking to your local motorcycle shop, stealership or whatever. Any good bike shop will be able to supply you with shims.

[GeeP]

You get shims from your local suzuki dealer.  Most dealers have a big selection stashed in the shop.  Many times they will trade used shims for the size you need, especially if you're a good customer.

If you go that route, be sure the shim has not been damaged.  The surface the cam rides on should be smooth and flat.  If it is pitted, rusty, or doesn't feel smooth as glass request another.  Rusty, spalled, or otherwise damaged shims can damage the face of the cam lobe during operation which will require a top end overhaul to repair.

Here's an example of what I'm talking about:

These are cam lifters out of a Continental aircraft engine.  (The lifter performs the same function in a pushrod engine as the shim in an overhead valve shim over bucket motorcycle engine.  The lifter on the left is OK.  The lifter on the right was severely rusted, then put into service.  As you can see, the surface of the lifter is spalled beyond repair.  The cam face must look "interesting" to say the least!

[Kerry]

Thank you everyone - great great responses and now I understand!

Glad to hear it!   

where do I get shims? Are the Home Depot type items or something I'd want to order from BikeBandit?

This is one of those "time vs money" tradeoffs.  If you have a local dealership you can get the shims "today" ... but they don't tend to come cheap.  Check multiple dealerships if that's a possibility; shim prices can vary significantly for some reason.  If you only need one shim you might try the "swap" idea that GeeP suggested.  But if you need more than one shim, you're kinda stuck.  I personally wouldn't take more than one shim out of my engine at a time, so "swapping" might mean multiple trips to the dealer.

If you're not in a hurry, the cheapest online source I have ever come across is [THIS ONE].  I haven't ordered from them, but a long-time GStwinner did [almost 3 years ago].  He said the cost was $5/shim + $4.50 shipping, but that "shipping costs a little less if you order by phone".  What with the rising price of oil, the shipping cost may have gone up since then....

If you don't mind me spending your money I recommend getting an additional "test" shim in the 2.30mm-to-2.40mm range ... for those times that a valve has NO clearance.  You can't get an accurate measurement (to help you determine which replacement shim to get) until you put in a shim that's exactly (or thinner than) what you need.  Most GS500s seem to come with shims in the 2.60mm-to-2.65mm range, so I have found the 2.30mm-to-2.40mm range to be a good thickness for a "test" shim.  Go any thicker and you may need to get a thinner one some day.  Go any thinner, and you have to use thicker feeler blades than is convenient.

Good luck!

[Jared]

Kerry's video is excellent ( as you've already seen ). Buy the tools....it's always good to have tools.Make them an early Xmas/Bday/whatever present to yourself...

You may also post on here if you know what size shim you may need...some of us have a small collection of swapped out shims in varying sizes.

My local dealer just swaps them with me ( or just gives..). It's such an old shop they have a stockpile...and I'm friends with them all there...

BUT make sure they are the right diameter as well as thickness. The GS uses a 29.5 mm diameter shim. For your test shim go with a smaller diameter shim as well ( easier to get in and out...I'm sure you saw/ heard that in Kerry's video ). Use a micrometer on each shim to verify the thickness stamped on it ( said in video I'm sure..). I haven't found a mislabeled one yet but if it's a swapped shim it could have worn a little...better safe than sorry...

It's not hard to do...