Ok, so a little back-story first.

I have a 1996 GS500E that I bought last year, and it has a bit of a performance issue.  I bought the bike used and the guy had documentation of a recent rebuild that included pistons/rings/valves/gaskets/etc.  I got a decent deal on it, painted it, and rode it.
Well, after getting more confident riding it and taking expressway I have discovered that it hates wide open throttle.  Not really an issue around town as I ride modestly, but it does cause issues on the highway as I can't open the throttle wide enough to get the bike fast.  It loses power when moving, but when free-revving it sputters, pops, and ultimately dies.
I thought it was a carb issue, and messed around with the jets, and ultimately never got it fixed, but it was never a serious problem for me so I just rode it anyway.


Well, now it's winterized at the machine-shop where I work, and I want to fiddle with it again.  I am nearby a shop that is supposedly the best Suzuki shop in Illinois, the proprietor goes by "D i c k" (stupid language filter) Speed, and I know people who know him well.  He said if I could bring him the head, he'd check the valves and springs and everything for me and help me diagnose the problem for free.

Great, and while the engine is apart, I figure go big or go home.

Now I don't really want to bore the block any bigger, but Speed can get me some domed pistons to change the compression ratio.  I am also going to rebuild the carbs proper and change all the gaskets, port and polish the head, and see if anything else deserves a change while I'm in there.  Then I want to get a Vance&Hines exhaust for it.



Anyway, here's what I want to find out.

#1  Where's the best place to find necessary information like torque specs and such?  Does Hayne's have a manual for the GS500?  Where can I find one?

#2  Speed said he doesn't have any aftermarket cams for the bike, but I could custom order some for around $700.  That's not gonna happen, I'm not dumping $1000 into this engine.  I'll spend a couple hundred total, but I know the bike will always just be a GS500 and as such worth no more than, like, $3000...
Does anyone know if any aftermarket cams even exist for the bike?  If no, I was considering buying some used cams either off of here or eBay, welding the lobes up, and cutting a cam myself.  If that is the case, does anyone have a custom cam they can give me any sort of dimensions on?

#3 I am pretty sure the last owner of the bike put a 15 tooth sprocket on it, and I don't like the RPMs the bike is in at highway speeds.  The factory is a 16 tooth, right?  Is it worth going up to a 17 tooth or should I just stick with the 16?  Also, where can I get these if duck can't get them for me?


Any suggestions or helpful procedures for getting the motor out/apart?  Seems pretty straightforward and it looks like the frame will partially unbolt and come out with the motor and everything, but I've never done this before.



Thanks everyone!  While I am going through with this I'll be sure to make a thread detailing it.  But I gotta find out more and talk to this guy a bit about what is wrong with it and what we can do to it.

1. http://cgi.stanford.edu/~sanjayd/gs500/Main/TorqueSettings

3. I run an 18t front, 39t (stock) rear and a 130/90-17 rear tire. 4k-5k RPM at interstate speeds and first gear actually seems useful now, but obviously you lose some acceleration on the low end.

www.megacyclecams.com

watcher just use î when spelling dîck. otherwise dîck becomes duck. had fun assisting pandy several years ago with the word filters lol. I remember this one lol. alternate characters weren't and more than likely wont be filtered. anyhoo my friend, back on topic, when she does this does it run hot?, you overhauled carbs right? I mean strip them down, remove plastic and rubber parts and soak in carb cleaner 12-24 hours?, aka a proper carb cleaning.

That link with the cams only lists to a 92 gs500, did I miss something and/or does it matter?


As for the carbs, I have taken them down completely, hand cleaned, and reassembled.  No soak.
Checked floats and such while I was in there.

I should mention the vacuum petcock doesn't exist, and there is now an inline valve.  The vacuum barb on the carb is plugged, and it doesn't leak, so I don't think its an issue but you all would know better than I.




Edit:



OK, so I've got the engine out and mostly apart.  Was easier than I expected, it seems like the whole design of the engine and frame is very intelligent.  Thumbs up Suzuki!  Got as far as taking the head off, and grand total from cover off the bike to tools back in their spots was only about 2 hours.



Couple of things I noticed.

Intake valves are gunked up a bit.  Maybe was burning a little oil, but they were rather white before I started messing with jets and now they are back to black.  Forgot to take a picture of them.
Exhaust valves are pretty white, again I forgot to take a picture.  But here is a shot of the top of the cylinder.




But the biggest thing that concerns me is the cylinder itself.  It looks like it was touched with a ball hone because of vertical as well as horizontal scratches, and it looks like there a bit of a gap between the piston and the cylinder walls.  I don't know how much there is supposed to be, but I did take a measurement of the bore diameter to get an idea of if it got bored out or not.
My boss helped me pull everything apart, and he grabbed a piston he had from his 570cc 2-cylinder snowmobile and it fit in my cylinders.  That caused some alarm for me; I do realize that stroke has as much effect on volume as bore does, but just the same I thought I'd run the number here.

Without taking the fouling off the edge, and using a caliper rather than a bore-micrometer, I got a diameter of 2.915 inches.  Can anyone tell me what the stock bore is?  Can anyone tell me how much it can be bored out?  Can anyone tell me proper piston clearance tolerance?

If I need to buy some oversized pistons then great, I'll hone out the scratches real nice.  But I need to know that I can/should.


Edit 2:

Found out on my own that the stock bore is 2.913 so I'm only 2 thousandths off.  Maybe 5 thousandths if my caliper measurement was a little off.  I'll hit it with a bore-mic when I get the cylinders off the block.

Your exhaust valves look like they might be burnt.  They are pretty white, at least indicating that you were running too lean.  I would rehone the cylinders, make sure your exhaust valves are sealing, check your ring end gap and piston size, and then make sure your have the right main jet and the carb is completely clean and air leak free.

Well this is what i think is wrong with your bike:

Have you ever tried to ride full throttle with the fuelcock on PRI?
I know the older GS500 sometimes have a leak in the fuelcock membrane, and since it is a vacuum system it starts leaking at full throttle which causes the carbs to run dry.
The easyest way to check this is to ride the bike with the fuelcock on the PRI position (the PRI function works without vacuum).

I hope this helps you.   

Quote from: dB-tje on November 03, 2013, 07:58:44 AM
Well this is what i think is wrong with your bike:

Have you ever tried to ride full throttle with the fuelcock on PRI?
I know the older GS500 sometimes have a leak in the fuelcock membrane, and since it is a vacuum system it starts leaking at full throttle which causes the carbs to run dry.
The easyest way to check this is to ride the bike with the fuelcock on the PRI position (the PRI function works without vacuum).

I hope this helps you.

Quote from: Watcher on November 01, 2013, 11:10:27 AM
I should mention the vacuum petcock doesn't exist, and there is now an inline valve. 

Thanks for the advice anyway, though.