1989 GS500e Carb - Carburetor Troubles and Woes

[alwaysmoreandmore]

Long time lurker here, thanks to all the contributors for all the other solutions, sorry that I'm too green to offer much help in other areas....

I'm also not sure which area is the most appropriate to post this in, so chime in if I'm in the wrong department (thanks)

While rebuilding my own carbs and trying to undue some jetting that causes too many issues and poor gas mileage, I found some hairline fractures in the body and choke tube (A Suzuki ex-tech thinks it might from CA's gasoline additives...), which may be why it runs way to rich and extra crappy at launch.  And Suzuki for some reason does not make the left hand carburetor (carb) anymore for those years, and the the right hand is on back-order indefinitely, so no way to buy new ones.

Keihin require a new push-pull cable system, which seems complicated and customized.  HK aftermarkets require some way to run them together in sequence.  The stores tell they can't ship non-USA carbs to the USA.  And apparently the GS500F is a hydraulic cable that faces the same issues as creating the one for the Keihins?

I am fully open to all suggestions, and would deeply love to get my 89, mild cafe' racer restitution back on the road and under my butt, this is the first stumbling block in a year long restoration where I couldn't find the part or the answer.  The Bay Area commute is eating away at my soul as I watch all the other cyclist drive by 

Idles fine, starts fine, but put it in gear and crap-oh-ramma.  Tested electrics, valves, timing, fuel lines, tank, airbox.  Carbs rebuilt twice, and after some help from a Suzuki Vet who the found the hairline fractures, is now really thinking that that is problemo uno for running too rich, and blackening the plugs.

Originally had the K&N airbox, dyno jet stage 1 (or 3?) and V&H pipe, 41 sprocket rear, ran hard up to the limit, everyone was happy (except my mom), but hard to keep in tune, starting sucking gasoline at 30 MPG or less, and then got worse until it back-fires so hard it nearly killed a homeless fellow, and now we are in repair-mode.  Now I'll like to dial all that jetting back and slow it down if that means better MPG and more stable engine use.

Thanks.

[Watcher]

Might want to get on the BST or Craigslist and start looking for donor bikes you can buy some carbs off of...  or eBay.

There's also a FaceBook group called "Suzuki GS500" that had some recent donors appear.

[Jim Moore]

If it was my bike I would put everything (including and especially the exhaust and airbox) back to stock. Then start again with the jets, all stock except one over on the pilot jet. The see if you actually have a problem. Carburetor tuning is  a tricky business. You can't just jam a bunch of aftermarket crap onto your bike and expect it to run right.

[The Buddha]

Long time lurker here, thanks to all the contributors for all the other solutions, sorry that I'm too green to offer much help in other areas....

I'm also not sure which area is the most appropriate to post this in, so chime in if I'm in the wrong department (thanks)

While rebuilding my own carbs and trying to undue some jetting that causes too many issues and poor gas mileage, I found some hairline fractures in the body and choke tube (A Suzuki ex-tech thinks it might from CA's gasoline additives...), which may be why it runs way to rich and extra crappy at launch.  And Suzuki for some reason does not make the left hand carburetor (carb) anymore for those years, and the the right hand is on back-order indefinitely, so no way to buy new ones.

Keihin require a new push-pull cable system, which seems complicated and customized.  HK aftermarkets require some way to run them together in sequence.  The stores tell they can't ship non-USA carbs to the USA.  And apparently the GS500F is a hydraulic cable that faces the same issues as creating the one for the Keihins?

I am fully open to all suggestions, and would deeply love to get my 89, mild cafe' racer restitution back on the road and under my butt, this is the first stumbling block in a year long restoration where I couldn't find the part or the answer.  The Bay Area commute is eating away at my soul as I watch all the other cyclist drive by 

Idles fine, starts fine, but put it in gear and crap-oh-ramma.  Tested electrics, valves, timing, fuel lines, tank, airbox.  Carbs rebuilt twice, and after some help from a Suzuki Vet who the found the hairline fractures, is now really thinking that that is problemo uno for running too rich, and blackening the plugs.

Originally had the K&N airbox, dyno jet stage 1 (or 3?) and V&H pipe, 41 sprocket rear, ran hard up to the limit, everyone was happy (except my mom), but hard to keep in tune, starting sucking gasoline at 30 MPG or less, and then got worse until it back-fires so hard it nearly killed a homeless fellow, and now we are in repair-mode.  Now I'll like to dial all that jetting back and slow it down if that means better MPG and more stable engine use.

Thanks.

Dude nearly all of this is wrong.

GS carbs are mikuni.
You're trying to buy the left carb from Suzuki WTH ? you wanna spend $2500 on a $1000 bike ?
What is HK Harman kardon ? No clue, and does not belong on a GS.
Gasoline additives cause a Hairline crack in the choke tube ? WTH do you think is in the gas in CA ? Sulphuric acid NO. Clutzy mech or other and I am guaranteeing you, its likely not an issue cos you're starting and idling OK.
And brilliantly that crack is making you run rich gotcha, CA air is so rich in fuel that when you punch holes in the carb wall you make it richer due to the extra gas in the air.
And the F is a hydraulic cable anyone ever heard of a carb operated via hydraulic cable guys ? maybe I've been asleep too long and missed some major technological advancement

All of it is BS, I am in the middle of a move, and 1/2 my carb crap is in the old house and 1/2 in my new house and am hamstrung. However I can guarantee you I can get your carbs back to working right.

If you have K&N needles in it and the whole rest of the K&N jet pack, it could be a great help but even so I can guarantee you, no more homeless people will be under risk ...

Yea ... I think I know why he's an ex-Suzuki mechanic.

BTW idles fine, starts fine - and put it in gear and it craps out = electrics. Specifically those neutral switch, side stand switch and clutch switch. Those control the spark etc etc when you put in gear. Idling and starting fine = choke is irrelevant. You're good on that.
You may be low on power at take off, you may be low on power through the mid range etc etc all that is carbs, but if you put it in gear and still have the clutch in and it craps out right without even trying to move, its electric.

Cool.
Buddha.

[qcbaker]

Like Buddha said, I would check the side stand safety switch. Thats the only part I know of that would cut spark when in gear but not in neutral.

[mr72]

There's more than just electrical that can cause the bike to not run right above idle but electrical is definitely the first to check. Since you've had the carbs apart a tear or damage to the diaphragm is also high on the list of what could be wrong, or a severe vacuum leak, like you left out the "little o rings" on the vac ports on the top of the carbs or you didn't put the caps back on. Just a few things to check once you verify electrics.

Seriously returning the bike to stock and start from there is your best bet. Get it running right stock then do your "upgrades" one at a time.

I agree the hairline crack theory is BS, and that's being generous. But if you find the hard parts of your carbs are toast I have a spare set that need things like o-rings and diaphragms replaced but otherwise are in fine working order. PM me and they can be yours for very cheap.

[The Buddha]

If he's got DJ kit and the original needles are gone, or a pipe/slip on without the stock exhaust lying around that "revert to stock" ship option has sailed.

Cool.
Buddha.

[mr72]

Good point.

Should be able to at least get it to run enough to diagnose jetting issues, valves, etc. once you verify no electrical fault and no vacuum leaks. Oh and don't spray carb cleaner on it. It'll eat up rubber parts that are critical to correct operation (the diaphragms, for example).

[The Buddha]

He's starting and idling. I think his problem is electrical. But he needs to come back and explain what all the stuff he posted means.
Cool.
Buddha.

[Jim Moore]

If he's got DJ kit and the original needles are gone, or a pipe/slip on without the stock exhaust lying around that "revert to stock" ship option has sailed.

Cool.
Buddha.

I hadn't thought about the needles but you can always find an exhaust on eBay for cheap. That's always the first thing I do when I'm trying to get a new-to-me bike running.

[The Buddha]

I hadn't thought about the needles but you can always find an exhaust on eBay for cheap. That's always the first thing I do when I'm trying to get a new-to-me bike running.

Stock pipe or slip on are jetted the same way. This isn't a big issue.
Needles from DJ are seriously tapered and they cant be used without some other funky jets from DJ.
Cool.
Buddha.

[Jim Moore]

I hadn't thought about the needles but you can always find an exhaust on eBay for cheap. That's always the first thing I do when I'm trying to get a new-to-me bike running.

Stock pipe or slip on are jetted the same way. This isn't a big issue.
Needles from DJ are seriously tapered and they cant be used without some other funky jets from DJ.
Cool.
Buddha.

That's interesting. Thanks.

[alwaysmoreandmore]

Thanks for the feedback.

HK = From Hong Kong, 33mm, supposedly can be strung together, but sounds way out of my league, I rather attempt fuel injection...

The Keihins were a thought because of Suzuki not making (for some reason) the left carb anymore or at least not shipping them to the USA.  Hopefully my intel that the stock carbs are Mikuni 33 BST is correct, and I was just wondering since the GS shares so many parts, that they may share the carbs with a 4-carber, but when I looked up the Katana and GSXR they were 34's or some other number, but looked so identical. 

Someone told me that the carbs on the GS500F, or 2006 and up were hydraulic lines in the throttle cable, and would take extensive tinkering to fit an 89, like getting the whole system from grip-throttle back to carbs installed and then there was the pipe too (was being helped to look for other options since Suzuki wasn't making them), which sounds crazy  but what do I know, the last carbs I successfully modified where on the YSR50 (well YSR80...), everything after that was failure after failure after failure.

My trouble is remembering all the right names for things (and that things have multiple names).  Also, I can't seem to add a picture attachment right now that might explain which part I'm referring to, but I think its the choke tube that sits in the float bowl, and it has a crack running down the side on each of the both carbs, one is about 1/2 way down, the other about 1/3 the way down.

I was trying before apparently ineffectively to speak in a bit of short hand...

Years back while parked in street bike got knocked over, made the muffler sound cool for a while but eventually the damage caused too much trouble, found that the cost of the V&H pipe, air-box and DJ kit and install was still cheaper than a stock fix, and the V&H pipe ran back to the engine (it was also oval and small and with a cool billet tip) where the Suzuki part was just the same slip-on for $400+, so why not have more power(?), the shop in SF said the kit was replacement jets and so on, and that these kinds of pipes need jetting, so there was supposed to be no drilling or permanent changes (sadly the parts [jets?] they gave back to me years ago have disappeared in the various moves).  However, as time passed the bike fell quicker and quicker out of tune, and ran richer and richer, and was more and more problematic, and just before it went kaput on me on the Bay Bridge, I had found out the some of the changes could not be undone.  So maybe a return to stock might work if I can put all the pieces together.

After sitting for a number of years covered in the garage, took it in and the compression test went well and valves seemed in good order, and a quick cleaning of the carbs and a new battery and wham bike comes back to life.  So I got to the other issues before tests rides cold commence (rebuild brakes, de-rust and seal tank, fuel lines, filters, petcock, tires, sprockets, chain (a really good chain too), clean engine & wheels, plugs, grips, fix lights & instrument panel, fix loose body work, reupholster seat) and ready for a test drive, which went OK until the bike got warm...

Starts up just fine and runs well while cold, sounds nice and throaty, once it gets warm, and or you try and ride it and/or take off the choke it all goes to hell, have to keep revving it, lots of gas smell out the exhaust, and when it dies, the spark plugs especially on the left are blackened (which I have led to believe is too much fuel).  So its not dying once in gear but it really runs terrible when I try to pull off.  Also new gas lines, new fuel filters (now dual), de-rusted and sealed tank, new petcock, new connectors/boots around carbs to seal up possible air leaks.

Still like that after the following repairs:

Tested or replaced a vast array of electrical - coils, igniter, rectifier, stator, signal generator, numerous plugs, and a battery.  Got all kinds of kind advice from many a parts seller along the way, things to try and test, and how to test.

Full carb clean and rebuild (except floats), twice, synced and checked for air leaks, pulled plugs after numerous runs looking for clues.

Am being helped by classic bike rebuilder (specializes in Triumph-Ducati) and has a friend trained at Suzuki years back in the era of my bike (no way to verify of course, both retired) to come in and take a look, a lot of head scratching and testing with meters, then pulled carbs, and began combing through them and found the cracks in the choke, and guess which one was worse, the left one...

(now the pics, thanks ben2g0 & Old Skool_R)

[alwaysmoreandmore]

Might want to get on the BST or Craigslist and start looking for donor bikes you can buy some carbs off of...  or eBay.

There's also a FaceBook group called "Suzuki GS500" that had some recent donors appear.

Noobie question - BST = Buy-Sell-Trade? (too many years not asking for help...), from this forum?  If so working on it.  And will definitely try FB, thanks

[mr72]

What are the compression numbers?  The way you describe it running sounds exactly how mine ran when it had bent valves. Maybe yours just has tight valves. Did you check valve lash? 

When the engine heats up and things expand the valve clearance (lash) is reduced and if it goes to zero then you'll have no compression and have to rev above 7k to make it run, then it dies and won't start again until it cools.

[The Buddha]

However, as time passed the bike fell quicker and quicker out of tune, and ran richer and richer, and was more and more problematic, and just before it went kaput on me on the Bay Bridge, I had found out the some of the changes could not be undone.  So maybe a return to stock might work if I can put all the pieces together.

OK this is a dead give away sign that your floats are drifting high. A DJ kit with a drastic taper needle will make it more acute than the stock one will.

The valves are possibly OK, they usually act up right after start up. Like 5 sec after starting up it will want to stall. If it got fully warm it will actually run very well.

Cool.
Buddha.

[mr72]

If it got fully warm it will actually run very well.

Well that's exactly opposite of what mine did, and exactly opposite of common sense.

With bent valves, my bike ran perfect fir like 10-15 minutes and then all of the sudden refused to run unless you revved it way high constantly, backfired on decel 100% of the time, and if you let the revs drop below about 7K it died and wouldn't restart until cool. A top end rebuild fixed it. I wish a valve adjustment would have fixed it.

[The Buddha]

If it got fully warm it will actually run very well.

Well that's exactly opposite of what mine did, and exactly opposite of common sense.

With bent valves, my bike ran perfect fir like 10-15 minutes and then all of the sudden refused to run unless you revved it way high constantly, backfired on decel 100% of the time, and if you let the revs drop below about 7K it died and wouldn't restart until cool. A top end rebuild fixed it. I wish a valve adjustment would have fixed it.

Oh yours was bent enough to stay open ? or just bent enough to bind after getting hot ?
I dunno about bent, I was talking about tight valves that are just tight enough to be at the 0 clearance limit.

Cool.
Buddha.

[Joolstacho]

I'm wondering if it backfired that violently, that could have caused the hairline cracks.

[The Buddha]

In the choke tube and nowhere else
Violent backfire strong enough to crack the choke tube in just that part of the carb, would have exploded the carb into 30,000 pieces.

I'll compare its likelihood to a guy being shot in the head and his head being intact and his toe nail cracking.

Cool.
Buddha.