GS500 basket case

[dylan13nnn]

First off.. hello i found the forum by googling the issues of my newly aquired 02 gs500.. seem like theres some clever people here so im going to hit you up for some tips snd hopefully start enjoying this basket case bike i just bought 

So i got a deal on an 02 gs500 with issues... being the cocky bloke that i am thought i would sort it and have a ridable bike.. doh! Got me bashing my head against a wall.. so i will break it down incase anyone clever here likes puzzles or if you prefer to just take the piss outta me thats cool too 

Symptoms.
Starts well cold with choke or half choke.  races to over 5k on full so usually use half. Warms up a lil rattly but not too shabby.. when getting close to running temp i back off the choke a bit and it starts running like a turd.. will not idle unless kept above 2k (by wharever means, choke , throttle, or adjusting idle screw up.).   Idles 20 mins then bogs down and stalls.. plugs show a rich condition. Can ride but gotta keep engine running at stop lights.. good top end power and highway speed fine.

What ive tested
Reset carb idle air screw to all in, then back off 2.5 turns on both carbs.
Checked operation of petcock.. diaphragm is operational with 'on' working when vacuum present and 'pri' working as just open.
Tested with fuel cap open = same result
Vacuum gauge (connected to both carbys) shows crazy vacuum bouncing all over the place (even to above zero) at bad idle but nice steady vacuum with very high choke idle or higher rpms held on by throttle).
Pulled valve cover , found timing to be correct and all valve clearances about within spec (on the sloppy side all between 0.05 and 0.1mm so atleast not tight!).
Compression test dry and cold 150/160 psi ..  warm and wet was slightly more.
Fuel hose and vac for petcock all correct
Air filter had a gut full of fuel (as did the crankcase because the gumby i bought it from was storing the bike in 'pri' and the floats were set waaay too high).
Oh yeh i set the floats down to the correct height and noticed that the carbs where surprisingly clean like someone had given them a once over . Checked o rings on idle air screws and a couple jets . Can shine light through jets. No junk in seats etc.. but i didnt overhaul the whole carbs due to the kits costing over au$100 for pair.. and CVs or carbs in general are not my forte lol.. if problem is the carbs seems like BOTH have bad idle circuits which seems unlikely i guess

I did check for vacuum leaks with wd40 but... i have not been suspecting vacuum keaks due to the rich (not lean) condition.. but the high idle on choke has got me confused..

Any thoughts anyone ??. Ive never seen a vacuum gauge behave like that in my life, litterally jumping from vaccuum to above 0 so fast the eye cant see bouncing around like that little needle is off his head.. but stabilizing above 2k rpm??. 
These bikes seem really cool and i cant wait to have a working one and customize it etc.. but right now i cant get the basics sorted.. i feel very silly.

[Bluesmudge]

Did you check the plugs before or after resetting the float height? Could have been two problems: Float height and vacuum leak. Did WD40 test result in anything?

The choke behavior sounds normal. The bike is supposed to sit at high RPM for a minute or so with the choke on full.

I did a search here and found two less common causes of hanging idle:
1.) Stuck throttle cable. Make sure it has slack when all the way closed.
2.) Timing off by 1 tooth. This one is really weird but may be something to check if you have exhausted all other possibilities. I'm no expert but could that result in weird vacuum behavior?

[The Buddha]

I suspect you still have high floats. And make sure those air jets in the back are clean - do not try to remove them, spray and clean em. Maybe use those hair sized cleaners.
Those let air in the pilot jet circuit. Less air = too rich.
Cool.
Buddha.

[mr72]

idling up to 5K is normal on choke. It's supposed to do that.

I think your float needles may be sticking. Usually when someone says "bogs" they are IME describing a lean/no-fuel condition that would actually argue that the float bowls are not filling correctly, so maybe low floats or float needles sticking closed. Maybe put it on the center stand on level ground and let it run a couple of minutes, enough to stabilize the fuel level in the carbs, then using a drain hose open the fuel tap on each carb bowl and measure how much fuel comes out. If it's about the same amount, then I'd carefully reset the float levels again and go ahead and probably replace the float needle valves while the carbs are apart just in case.

Oh one other thing, if the pilot needle o-rings are shot then it will run rich on pilot no matter what you do. And they are probably shot.

And while I'm at it, the intake boot o-rings are probably also shot, and will leak air acting like a vacuum leak and making it run super lean under load.

I'm sure you've seen this but it might help if you haven't:
https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html

[The Buddha]

The drain and measure is not a good test. The fuel in the line is a significant portion and the bowl you drain first will have a higher volume - by a good bit.
Do U tube test, in prime for float level. Use a clear tube if you can.
Float needles also are near impossible to stick closed. The fuel pressure sitting on top of them will push them open. The 01-02 carb has many flaws, but the needle sticking open is unlikely to be one of them like the 89-00 version.
So its likely your floats are still high. Pilot needle O rings ? I have no idea what these are - I've never seen these cos carbs don't have a "pilot needle". The only needle there is goes through the main jet. We mistakenly refer to the float stopper as float "needle". Even if it was the pilot jet - there is no O ring on the pilot jet - never has been, 89-00 nope, 01-02 nope, 04-09 Nope.

Intake boot O rings or intake manifold leak will cause it to run lean not rich.

Cool.
Buddha.

[mr72]

the thing you often call the "pilot screw" is the "pilot needle". it's a needle that goes in the pilot valve. Jut happens to be threaded and adjustable with a screwdriver. and it has an o-ring that will cause rich running if it's bad.

and I really do think I specifically said the intake boot o-rings being bad will cause it to run very lean. you read my post at all?

I'm going to have to stop clicking on that "Show me this post" link and leave some folks on hide.

[dylan13nnn]

Thankyou all for the suggestions.. as previously mentioned timing is not a tooth out.. its spot on.. float levels where high previously but i set them correctly, and allready used a capillary  ( 'u hose' method) to confirm.  Plugs where replaced after initial going over sorry forgot to mention.. still read rich..  i .might try a damper in line with the vacuum gauge as i since realised it may need one    i dunno.. but appreciate you guys offering advice
Mr72 are you talking about the smaller jet inside , revealed when float bowl is removed?. I cleaned / checked that. No o ring present on either carb. Should there be ?. Like i said im not into cvs or carbs as i previously mainly played with cars.

[mr72]

Read the blog post I linked above. If you remove the pilot needle (what you used to adjust the pilot mixture to 2.5 turns out) completely, then out comes a spring, a washer and a tiny o-ring in that order. That's the o-ring I am talking about.

[dylan13nnn]

Sorry mate.. a terminology thing.. i was calling that an idle air mixture screw cos im not too familiar with cvs. Yes i can see that would make it rich.. good suggestion but there fine. Damn

[Bluesmudge]

Are the jets the stock size?
When you were setting the float heights, did the float needle valve seem like it was functioning properly? Kinda springy and clicky.
Did you use any carburetor cleaning products while you still had rubber parts in the carb?

Have you looked at the other side of the carb where the diaphragms are to see if they are in good condition and if the previous owner put any washers under the needle or incorrectly assembled something. I once had a bike run like crap after cleaning the carb. Turned out I put one piece back together wrong; the little plastic piece that the spring sits on was under the needle clip instead of over it. It can be helpful to reference the parts fiche upon reassembly instead of relying on the previous condition and your memory as a guide.

[dylan13nnn]

Bluesmudge. Thanks i have not sprayed any non metalic parts.. carbys look very clean like PO had a crack at it.  Not sure if the jets are stock as the numbers on them are not the size..(eg. 40. More like 'REU' or something written on them) like jiberish to me??.
I believe the issue is pilot curcuit  related as higher rpms are crisp and responsive.. slides jump up when twsting the throttle and fall back down nicely, main jets seem to be handling high rpms fine if i understand the carb correctly.
I havnt opened the top (diaphragm section) as i thought this could not affect idle or cause the rich idle and stall condition. But hit me up if im dead wrong please!
I will do as suggested earlier and clean the pilot air holes in the filter side of carby to see if it helps.. thanks all for your thoughts.

[cbrfxr67]

weeee welcome,...always fun to read about someone getting it running,...especially when it's not me

where pics?

[mr72]

I believe the issue is pilot curcuit  related as higher rpms are crisp and responsive.. slides jump up when twsting the throttle and fall back down nicely, main jets seem to be handling high rpms fine if i understand the carb correctly.
I havnt opened the top (diaphragm section) as i thought this could not affect idle or cause the rich idle and stall condition. But hit me up if im dead wrong please!

Probably on the right track. Just remember not to spray any carb cleaner on/in the carbs while the tops and diaphragms (or any rubber parts) are still installed. Before hitting it with any carb cleaner you need to tear it all the way down to the metal core of the carb with all o-rings and diaphragms removed. Carb cleaner will immediately damage the rubber diaphragms and will degrade o-rings.

I will do as suggested earlier and clean the pilot air holes in the filter side of carby to see if it helps.. thanks all for your thoughts.

I would think if these holes are clogged then it would be very hard to start and it wouldn't idle at all. The fact that it'll idle up to 5K with choke when cold tells me it's getting plenty of air at idle.

Truly here are my thoughts:

1. you may be just turning off the choke too early. It can take 15-20 minutes of actual running on the road, going through gears under load, for the bike to get to operating temperature. My GS500 (old version of carbs...) will not idle like without at least some choke until I have ridden about 5 minutes. So maybe you are just getting in a hurry to get it off choke and there's nothing wrong.

2. You might still have an air leak at the intake boot o-rings, which will add air variably according to load/throttle/rpm and totally screw up mixture settings. And you might have inadvertently compensated for this by making the idle too rich.

3. Something in the pilot circuit is clogged. The jet can get clogged easily, so can the channels that feed fuel to it. Or the air orifice as suggested. In any case you sort all of this out quickest and easiest by just tearing down the carbs and re-cleaning them in their entirety, replace o-rings, and reset. Trying to debug one little thing can be a fool's errand.

[dylan13nnn]

Cheers 72 .. #3 might be it...  i have removed the boots now and o rings are definitely suss! A busy couple days coming up and it 46 degrees c outside so bugger that! but hopefully I get around to replacing and reassembling to see if thats the issue...  symptoms all line up to vac leak but the wet sooty plugs have been steering me away from it indicating rich not lean... BUT... it has only ran on choke .  So that may still make them read rich as turning choke off kills it (yes even after 10 . 20 or 30 minutes but thanks for pointing it out.. there are no silly suggestions).
CBR pics at the moment would be of gs parts and tools scattered accross my veranda  haha.. but il post pics when its  running and i start on cosmetic mods.. gonna be a rat bike so i dont have to park the sporty anywhere dodgy.. hahaha

[The Buddha]

The pilot jet sits in the bowl. There is no channels that feed to it. Its sitting in the float bowl, and the pilot jet orifice is several times smaller than the passages. Very unlikely fuel gets through the pilot without clogging it and clogs up the passage which is literally 2-3X the diameter of the hole it just passed through.

The choke circuit pulls fuel through the pilot jet. If its rich on the choke, its not plugged in it. If you want to try experimenting, put a rubber plug in place of the pilot jet and see if it will even start up on the choke. Plugged pilot = no running on choke.

I'm not sure if you tried the wd40 test for vacuum leak at intake manifold.

The air mixture screw passage could be blocked, or you may just have the throttle stop screw all the way out so its shutting the throttle completely instead of leaving a crescent when you shut the throttle.

Trouble shoot first before randomly taking stuff apart - though just by sheer luck you might get it right much faster taking apart and cleaning stuff. You have a counter intuitive problem here - or atleast a not too common one.

Cool.
Buddha.

[mr72]

The air mixture screw passage could be blocked, or you may just have the throttle stop screw all the way out so its shutting the throttle completely instead of leaving a crescent when you shut the throttle.

.. which is pretty much exactly how its meant to be set up, the entire purpose of those air orifices in the venturi.

[The Buddha]

The air mixture screw passage could be blocked, or you may just have the throttle stop screw all the way out so its shutting the throttle completely instead of leaving a crescent when you shut the throttle.

.. which is pretty much exactly how its meant to be set up, the entire purpose of those air orifices in the venturi.

Sorry no, If you don't have a crescent shaped air gap, you will not hold an idle. It would not idle with the butterflies closed.

The inlet jets in the air filter bell mouth - not the venturi allow air air to enter and fuel to mix and atomize and come out in a smooth misty spray into the air stream passing through the venturi instead of a pure stream of just gas.

Cool.
Srinath.

[dylan13nnn]

Hey all.. thanks for the suggestions looks like it was a vacuum leak after all (intake o rings). I feel silly but spraying the intake boots while running failed to change idle and the black sooty plugs just steered me away from a lean stall.. i guess the previous owner riding it around on choke all the time may have caused this ??. Then when i swapped out the plugs i would be running it on choke for 20 mins then less than a minute without choke before it stalls so thats why the plugs always read rich.. i guess in my head i would have expected vac leak to look like 'dry" lean plugs and high idle (hanging idle).. live and learn thankyou for all your suggestions.  At the least some msintenance is done ive got clean jets, valve clearances are checked, fresh oil and new plugs. So theres that.. haha..
Onto the next problem.
With a stable idle the 'little rattly' i mentioned in my initial post is a really noticeable knock at idle that goes away at higher (about 2.5k) rpm then sounds fine.  Easier to trace with a screw driver used as a stethoscope now.. left engine cover..    ..... drained the oil again to remove left (alternator) cover and inspect... appears the "starter clutch" behind the magnet drum moves about 2-3mm back and forth when manipulated by hand, sounds an awful lot like the knock I hear at idle. . Possible its bolted on loose ?.  Im off to borrow a puller from my brothers workshop and remove the magnet drum n check it out.  I hope its as easy as tightening bolts and adding some red thread locker..  that would be great..
As a side note theres seems to be a mm or so of end float in the crankshaft.. (guessing a mm i dont have a dial indicator here) (actually there was on the intake camshaft as well come to think of it)..  i cant find anywhere what the spec is for float on this engine but i sure hope that isnt my knock.. thaat would suck!
Il report back when its running like a clock (being cocky again hahaha).

[The Buddha]

Likely not the starter clutch.
Starter clutch will make a hard metallic knock at start up if slipping, usually if its locked up, it will destroy the starter in a matter of minutes. Any other state of malfunction in it is extremely unlikely.
The magnets are intact ? then leave that assembly alone. Do not try to pull it with a sliding hammer (correct tool, or a dent puller - likely wrong tool, or some other gear puller - very very wrong tool)

The upper cam shaft to bearing end play having 1mm end play is almost normal, and will make a clacking sound at and just off idle. Nothing to worry about. But they do sell shims of 1.1mm and 1.2 and 1.3 to quieten it down.

I suspect your clacking is the only issue - and hence its done. Clacking at idle and just up off idle is there in ever bike, worse in the post 2000 ones due to shieite manufacturing form spain or wherever they made them.

Cool.
Buddha.

[The Buddha]

And the only part I believe bolted in that left cover outside of what is bolted to the cover is that rotor to the end of the crank. The clutch is bolted onto the back of the rotor, it being loose will not allow the thing to start at all. The idler is on a pivot and the starter is bolted in on the other side in the cavity under the carbs.
I suspect the starter clutch bolts being loose is what you suspect, and those if loose will hit the engine case in short order and you'd end with a lot of shrapnel and a DOA motor in very short order, pretty sure its not happening.

BTW is that pinned/riveted on or bolted on ? Check it - if its pinned on, you don't need to remove it to check if a bolt is walking on you.

I have seen it both types even just on Suzuki GS based bikes, the katana motors were bolted on but an entirely different type, not the sprag like we have, something stupid with 100's of teeth and if you ever let those get out, you cant tell which way each tooth goes and no way to even hold it together. A Suzuki savage OTOH has similar teeth, but they're held in by a wire running around and cant escape.

Cool.
Buddha.