A loose exhaust valve is a happy exhaust valve.

[gsJack]

If you want 100,000 miles or more without a valve job from your GS500 ponder this.  If you consider your GS a beginners bike like Suzuki does and plan on replacing it with a real bike as soon as posible just ignore.

Did my 80k mile valve check yesterday and replaced one exhaust valve shim because the clearance had just dropped below the .003" max spec (.001-.003").  First shim change since 40k mile mark on my 02 GS and all shims are still in 250-260 range with many miles to go before the exhaust valves receed into the seats and reach the min 215 shim like one on my old 97 GS did by 80k miles.

After replacing 2 shims on one of my 02 GS exhaust valves at 30-40k miles I decided to set them a bit looser to give more cooling time on the seats and it worked.  A stock GS engine reaches peak HP at about 8500 rpm and nothing is to be gained going above 9-9500 rpm so I set them at .003-.005" like they did on my old 82 CB750 shim over bucket valve adjusted engine with a 9500 rpm redline.  If your going to the track to redline your modified GS all day long just ignore this all as the opinion of an old man and do it Suzuki's way.  

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

[burning1]

Actually, I was interested in this. .03mm is an incredibly small gap. I'm used to seeing .20mm-.30mm on my other bikes.

[tt_four]

Are the newer ones different? Mine is a 1991 and I thought the proper clearance was .003-.008, which would leave your .003-.005 still on the tighter end of things.

[Paulcet]

tt:  mm vs inch!

[burning1]

Are the newer ones different? Mine is a 1991 and I thought the proper clearance was .003-.008, which would leave your .003-.005 still on the tighter end of things.

Mixing up units. OEM clearance is .03mm - .08mm, which equates to .001" - .003".

[tt_four]

gotcha, I wasn't paying enough attention to see the ", I actually believe I hate SAE measurements that I probably blocked the symbol from my sight. Jack, do you know off the top of your head, so I don't have to break out the paper and pencil to do the math, what clearance you setup in the metric measurement? I'm guessing you're in the .08-.11 range?

[romulux]

I'm running loose, as well.

LE 0.07mm
RE 0.10mm

[ohgood]

i love how the mm guys are all "imperial is hilarious nonsense !" until you get small... then they might as well use inchers, just like us..


at work, tons of prints come in with metric tolerances, surface finishes, etc and there is a BOOK to define each one with charts and such. i honestly don't know how one operates a machine in mm-land without said chart.

that being said, loose exhaust sounds like the way to be for me.

[gsJack]

gotcha, I wasn't paying enough attention to see the ", I actually believe I hate SAE measurements that I probably blocked the symbol from my sight. Jack, do you know off the top of your head, so I don't have to break out the paper and pencil to do the math, what clearance you setup in the metric measurement? I'm guessing you're in the .08-.11 range?

.003"x25.4=.076mm and .005"x25.4=.127mm or approx .08-.12 mm for the exhaust valves.  I just leave the intakes at the standard specs.  They don't run as hot and receed into the seats like the exhust valves do and rarely change at all. I've been using sae measurements all my life and think in inches rather than mm.  I can remember back in the 50's we started converting and put both inch and mm dimensions on drawings where I worked thinking metric would soon be in universal usage.  Took a long time to catch on in the US.

[burning1]

i love how the mm guys are all "imperial is hilarious nonsense !" until you get small... then they might as well use inchers, just like us..

Imperial units are fine, so long as you stay away from fractional inches and any value that requires unit conversion. 

[tt_four]

yeah, while I'll admit I think it's dumb that there's 12 inches in 1 foot, and 3 feet in one yard, I can handle that stuff, it's when you start to get into 3/16 and 5/8 and 1/4 and 15/16ths. It wouldn't be as bad if everyone just used decimals, but they don't. I don't understand why anyone would want to try out a wrench, and instead of saying "ooh, this 15mm wrench is one size too small, I better grab the 16mm, they'd rather try to remember that 5/8th is one larger than 9/16ths. Nonsense.

I was depressed for a week when I realized that Buells are half imperial and half metric, but I guess I'll survive.

[commuterdude]

At work we have some Monarch EE lathes with metric feeds built right into the gearbox.   Fun to play with.

[bill14224]

.003"x25.4=.076mm and .005"x25.4=.127mm or approx .08-.13 mm for the exhaust valves.  I just leave the intakes at the standard specs.  They don't run as hot and receed into the seats like the exhust valves do and rarely change at all. I've been using sae measurements all my life and think in inches rather than mm.  I can remember back in the 50's we started converting and put both inch and mm dimensions on drawings where I worked thinking metric would soon be in universal usage.  Took a long time to catch on in the US.
[/quote]

Glad to hear your valve seats are wearing nice and slowly, Jack!  I intend to do the same thing, that is, find out how many miles I can put on this thing.  It's been two years and I like this bike as much as any bike I ever had.  It's perfect for everyday use.

As for the metric system not completely catching on, I can explain why.  The metric guys haven't won any wars in ages, and the way they're going, never will again.  As for the arcane nature of the Imperial system, is it really that hard to remember that 5/8", which is 10/16", is more than 9/16"?  If so, that would explain why the metric guys need us to protect them.

[DoD#i]

Mind you, get back to older inch products like wood auger bits and they were simply marked 4, 5, 6, 7, 8, 9, 10, 11... - the /16 was known but not marked on the tool, and the user was expected to know that an 8 would make a half-inch hole.

If you were goofing off during fractions in grade school and can't figure out that 5/8 is 10/16 and thus bigger than 9/16, that might provide a good deal of insight into the other thread about dealer mechanics buggering carbs...   Then there's the bit about racking all your sockets/wrenches in order of size, and always putting them back, so that you don't even have to look at what size the socket/wrench is, you just try the next bigger/smaller one, and switch form the inch set to the metric set (or vice versa) if that doesn't do it. I suppose the brave could rack by size without keeping inch and metric separate, but I'm not going that route.

Print this out and put in in your toolbox - or you can get nicer ones (with number and letter drill sizes, too) from any machine shop supply: http://www.hamuniverse.com/antfrac.html Or you might find this one better: http://www.labeldotcom.com/CMSFiles/Image/Tips/Fraction-Decimal-Millimeter-Chart/Fraction-Decimal-Chart.jpg

This one actually works both directions and has number/letter sizes: http://www.davehylands.com/Machinist/Charts/Drill-Conversion.pdf

The one that gets me annoyed is the mixing, where the bolt that's too small for 1/2 and too big for 7/16 is the 12mm in the midst of a bunch of inch fasteners. Then add chinky-Chinese sloppy tolerances, and who knows what wrench would actually fit it correctly. Got the 11.93mm or the 12.13mm in the tool box?

[Pigeonroost]

If they ain't tappy, they ain't happpy!  lol

Jack, another possible "trick" is something I think Buddha may have mentioned some time ago, using a top end oil in the fuel.  Maybe an ounce or so per tankfull of MMO or a good air cooled type of 2 cycle oil or Lucus fuel treatment.  The theory being that this somehow "cushions or seals" the exhaust valves as they contact the seats.  I dunno.

Have you noticed any performance loss in the low to upper midrange with this mod?

prs

[gsJack]

Pigeonroost, I haven't noticed any performance loss at all with exhaust valves set as loose as .004-.005" on my stock 02 GS500 nor have I heard any increased valve tappet noise.  Like burning1 said above the .001"/.03mm min Suzuki spec is an incredibly small gap.  Difficult to even measure with feeler guages I think.  The .002-.005" spec of my old shim over bucket CB750K was a more reasonable one to work with but that bike had a 9500 rpm redline.  Had a couple of old early 80's CB/CM400 twins with screw adjusted valves and they were set at .004" intake and .006" exhaust.  Living with my first GS500 I came to appreciate why they set the exhaust valves looser.

I have no idea at what increased gap and high rpm combination that throwing a shim might be a serious concern but have seen pics of mc engines that threw a shim and they were a mess.  I try to caution not to go wider if you're going to run at 10-11k rpm very often or very long.   A well modified GS engine with proper intake, exhaust, and jet mods will carry near max HP well past 10k rpm but the HP of a stock GS will nose dive above 9k rpm.   I think a 11k rpm redline for a stock GS500 with it's decades old 2 valve engine design is increadibly high.

[burning1]

I dont think .12 is such a wide gap that you're going to run into problems; the shims sit fairly deep in the valve buckets and the only way they'd get anywhere close to slipping out is if you were experiencing pretty bad valve float.

With that said, I think the GS engine could be pushed a little higher than 12K with the right rods, and bearings. At 11K, there's a lot of stress on the wrist pins, but the bore/stroke figures are actually a little more over-square on our GS than they are on a 09 GSX-R 1K. Valve float could be a problem, but I think it could be resolved with titanium valves, stiffer springs, and a shim under bucket retrofit.

[burning1]

Thanks again for the info, gsJack.

I had a spare set of shims for my exhaust valves handy, and just spent a couple of hours last night adding an extra .05mm of clearance.

[Pigeonroost]

I think I will shoot for .1mm on the exhaust when I re-visit the job next (forgive me for saying the "W" word) winter.

prs

[the mole]

Thanks for the post Jack, I'll be going the same way at my next adjustment (due soon).