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**bwringer** · 11-18-2005, 12:55 AM

Um, I just bought a set of metric feeler gauges and saved the angst... you can get them at any Pep Boys or Advance Auto. They don't include smaller than .04mm, but I don't like having clearances that small anyway.

Anyway, one of your assumptions is dead wrong. If you must be a little off one direction or another, you want the valve clearances to be looser rather than tighter.

As the valvetrain wears, the clearances can decrease or increase. And it's actually more common on a GS for the clearances to decrease.

The function of having clearance specs at all is valve cooling -- the valves must stay in firm contact with the seat long enough to transfer their excess heat into the cylinder head. If the clearance is a little loose, the cam lobe makes a little more noise as it contacts the face of the shim, but with decent oiling a little noise is harmless.

However, if the clearance is tight (and .03mm is about as close to zero as you can get), the valve can't make good contact with the head, it heats up and gets softer, and exhaust gases start to erode canyons into the leaky edges of the valves. This is not good. Trust me on that...

On average, clearances tend to slowly decrease on a GS, and the process is faster on the hotter exhaust side of the head. On the whole, things are pretty well balanced, so that most bikes go tens of thousands of miles and only need one or two shims replaced. However, you still have to check them as specified (every 4,000 miles, I think) because you just never know.

Increased clearances are the result of wear to the cam lobes. Wear faces on the shims are much harder than the cam lobes, so there's normally no detectable wear on shims. This can be minimized with good oil and good oil supply to the camshafts.

Decreased clearances are usually caused by wear to the sealing edges on the valves. In older engines, you'll notice that the hammering over the miles has slowly caused the margin at the edge of the valve to get sharper and sharper from millions of impacts with the seat. Since the sealing surfaces are conical, sealing is not affected, but valve tend to recede into the head slightly over the miles and cause clearances to decrease.

**bwringer** · 11-18-2005, 01:13 AM

To answer your concerns more directly, I am also rather anal about valve clearances, and I don't feel that a clearance on the lower edge of .03mm is acceptable.

However, a clearance right on the edge at .08mm is just fine -- it will likely tighten up slightly over many thousands of miles anyway.

To really get in that nice comfortable .05mm - .08mm range, I have found a couple of tricks. One is obvious -- the "x" shims. You can't order these, but many bikes came from the factory with slightly fatter shims marked with an extra "x'. For example, a shim marked 2.75x would actually measure 2.77mm or 2.78mm. If you can somehow find a stash of original traded shims, the mysterious "x" shims can be very useful for helping us anal-retentive souls set clearances more accurately and get to sleep at night.

A second discovery is that the aftermarket shims are often a little thicker than marked, much like the "x" shims. The ones I get from Cycle Recycle II are normally .02mm thicker than marked, while Suzuki shims are normally dead on. The aftermarket shims are just as hard and excellent quality, so I use them when I need that last tiny bit of accuracy. They're only $5 each, so I usually buy the one I think I need plus one or two extras on either side just in case and for the future.

By buying extras and scavenging, I've built up a nice little collection of shims now, and I haven't needed to buy more for the last three or four adjustments.

Finally, you need an accurate way to measure shims. Always verify the markings. You will go absolutely nuts and make a lot of errors if you try to use an old-fashioned micrometer marked in inches and then convert to mm. I spent a whole $16 on a Chinese-made digital caliper that reads in mm or inches and is extremely accurate and repeatable. These are pretty easy to find at Harbor Freight, on eBay, or anywhere cheap Chinese tools are sold.

**KEITH KRAUSE** · 11-18-2005, 01:14 AM

I use a metric gauge.
Always "err" on the loose side.
Keep a record of all shims in service. You may find that you have more than one specific size of shim. They may not be exactly the same thickness and swapping them may help you.
Also, there are "fat" shims available. These should have an "X" after the number. A fat 2.55 shim may measure 2.56 or 2.57.
Hopefully, you followed the valve clearance check/procedure according to the factory manual. Some members turn the motor over and over and insist on taking every read with the cam lobe pointing up. This will yield inaccurate reads in my opinion.
Also, the motor must be STONE cold before checking. Overnight is best.
PS: bwringer, I was still typing this when you sent your second post. So there's some duplication.

**bwringer** · 11-18-2005, 01:20 AM

Yeah, what Keith said, too.

Keith, is it possible to order X shims, or do they have to be scavenged from traded shims or scrapped engines? Legend has it there are no part numbers for these, but if you've found a way to order them, let us know what the trick is. Does it involve six packs for the parts dept.?

**KEITH KRAUSE** · 11-18-2005, 01:55 AM

Originally posted by bwringer

Yeah, what Keith said, too.

Keith, is it possible to order X shims, or do they have to be scavenged from traded shims or scrapped engines? Legend has it there are no part numbers for these, but if you've found a way to order them, let us know what the trick is. Does it involve six packs for the parts dept.?

I've never ordered an X shim. The ones I've come across were just mixed in with the shops used shims. They do come in handy.

**BRycraft** · 11-18-2005, 10:08 AM

Valve Shimming

Thanks to everyone for your help, I am glad I didn't put the cover back on. This helps a great deal as now I can go with the thinner shim and have a little more play and not be concerned and sleep at night.., I had a hard time finding feeler gauges that even go as thin as .001, everything I found at the auto stores only goes to .0015 and Suzuki wants like $25 for their gauges and for just that 1 gauge for .001 wasn't worth it,.... I assumed wear would cause an increase over time because I realize the shims are harder wearing the the parts they are up against, and I appreciate getting that cleared up. I did notice some of the shims I have do have an X on them, I had no idea what that meant.
Thanks again to everyones input, this has helped me out a great deal...
Bill

**AOD** · 11-18-2005, 02:17 PM

If the clearance is a little loose, the cam lobe makes a little more noise as it contacts the face of the shim, but with decent oiling a little noise is harmless.

My engine isn't exactly quiet due to keeping the valves on the 'looser' side, but that's best for performance as well as the heat transfer mentioned above.

One thing for those considering this, you may not need to go out and buy shims (I forget how much they are a piece if you try and order them new) if you find the shims in your bike won't work. Give your local Suzuki shop a call and ask if they have any of the old silver-dollar sized shims still.

Back in Illinois (Lombard Suzuki) they had a storage bin full of shims all organized by size. I gave them the shims I did not need and took the ones I did. Worked great.

~Adam

**Guy** · 11-18-2005, 04:44 PM

I use a pair of metric feelers to check the valve clearances: 0.05mm and 0.10mm. I consider a valve to be ok if the smaller feeler will fit but not the bigger one. Always err on the loose side.

**bwringer** · 11-18-2005, 08:15 PM

One fine day, I called every Suzuki dealer within 150 miles of central Indiana. NONE of them stocked shims, even though there's a current model (GS500) that uses the same shims. Plus I got a lot of unwanted guff from the morons staffing the parts counters.

Anyway, a small bulb eventually started to glow weakly, deep in my fevered brain, and then I thought to call Cycle Recycle II, located just 20 minutes from my office...

Some of the grubby independent motorcycle shops that have been around a while might have a supply of shims, although I haven't found any that will trade. No thanks -- I'll just buy new ones for $5 from CRC2.

**AOD** · 11-18-2005, 09:46 PM

Anyway, a small bulb eventually started to glow weakly, deep in my fevered brain, and then I thought to call Cycle Recycle II, located just 20 minutes from my office...

I wish I could visit that place...they're the best. I look no where else usually...

**bwringer** · 11-18-2005, 11:35 PM

Originally posted by AOD

Anyway, a small bulb eventually started to glow weakly, deep in my fevered brain, and then I thought to call Cycle Recycle II, located just 20 minutes from my office...

I wish I could visit that place...they're the best. I look no where else usually...

CRC2 is as chaotic, crowded, dank, and grubby as you can imagine. It's in an ancient building in the bad part of town (well, as bad as Indy ever gets), and the owner chain smokes while answering the constantly ringing phone, patiently explaining the proper use of obscure parts, and barking orders to his assorted minions. It's actually very organized, but it looks like an explosion in a motorcycle factory at first.

Most of you know CRC2 from the web site (which is also sort of chaotic), but their primary local business is selling used parts. You have to call if you need a used part, but there's an excellent chance they'll have what you need.

They also have a huge motley assortment of aftermarket and NOS parts and accessories from back in the day. The hundreds of side covers hanging from the ceiling are very interesting -- there's a healthy GS section just to the right of the counter.

CRC2 is also the friendliest, most genuine and polite business you will ever visit. No matter how long the line is, they always make sure you understand completely what you're buying, that you have the correct part, and that you how to make use of it.

The other customers are always fun to talk to while you're waiting, and no one seems to mind waiting a little while. You know you're going to get the same level of attention when it's your turn, and Rob has a deep, booming voice, so you can pick up a lot of valuable information while listening to him give advice to someone else.

I love having an excuse to go down there, even if it's just to buy oil and a filter.

**themess** · 11-21-2005, 09:33 PM

valve adjustment

I looked it up and .003mm is in fact .0254in and to get the conversion from metric to inches you take the mm and divide by 25.4 or take the inches and multiply by 25.4mm or take mm X.03937, this changes the specs to a more accurate reading.
in reality .001in=.0254mm NOT.03 and .003in=.0768mm NOT .08 now this may seem trivia

Just to make it a bit more confusing:
A feeler gauge marked 0.003" is not 0.00300" thick. The manufacturer has tolerances and probably holds it between about 0.00275" and 0.00325" thick. That's part of the reason that the metric-to-English conversion wasn't precise. The engineers know that variation from one set of feeler gauges to another is at least as big as this difference. The engineers who design the engines and write the specs consider typical measurement errors when writing the specifications.
Factories routinely check the accuracy of their measuring tools. The most accurate tools, the 'standards', are used only for checking the accuracy of the other tools. A factory's standards are checked regularly against standards maintained by companies that regularly compare their own standards against national standards. For a fee, you can get your gauges checked and measured, but I guarantee, you don't want to pay that much!

Tom

**saaz** · 11-22-2005, 12:37 AM

I have kept old shims over the years so I can measure each one with a micrometer to determine its actal size. Then I use the one that fits best with the valve measurement. I also measure my feeler guages with the micrometer to see what it actually is.

**themess** · 11-22-2005, 10:09 AM

tolerances

A micrometer allows you to compare different sets of feeler gauges and shims, and lets you compare them to each other. But

> It has to be used properly.

and

> The micrometer itself was manufatured to tolerances, and its reading of 0.003" isn't exactly 0.003". Diffferent micrometers give different readings.

Tom

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