Press fit part around top of carb slide, query...

[user11235813]

Here's a photo of what I mean below.

OK my stalling and backfiring problem returned with a vengeance and I thought it's either electrical which I can't diagnose or somehow it's the carburettor even though I've pulled it apart and it looked good. So...

I took in into the Suzuki shop to let them diagnose it. They said it was a carb issue and that it's not repairable as it was to do with a 'press fit' part that the slide runs in and apparently it was leaking vacuum around that. They said they pressed it back in as best they could but it's only '85%'. They had a carb off a 2011 they could replace it with. I said OK but then I got the horrors and changed my mind, it was too old and I would have wanted to check it.

I found an excellent condition carb assembly with only ,3000kms on it for what they were going to charge me. So I have ordered that and it's on the way. I guess that will give me some spare parts as well as the slides and diaphragms were all good.

Anyhoo I'll have that delivered in a few days and then I'll know for sure.

However, I had to pull them off off when I got the bike back because it looks like it was worked on by a trained monkey. The fuel drain hose was not plugged into the bottom of the tank because I just put it back together before I took it in and I left it off on purpose just to make sure that wasn't causing any problem. When I got the bike back first thing I noticed was the airbox drain was completely pinched closed. Not a big deal but pretty sloppy.

Then I saw that the reserve fuel line was routed incorrectly and so it was jammed into the vacuum hose and looked to be almost pinched shut. Great. So I had to pull the tank off and then I noticed that not only had they not reconnected the fuel overflow/drain hose but they just pulled it out and threw it away. Then I saw that the end of the airbox drain hose instead of being routed down the side of the bike in it's little clip was instead routed down the back of the bike and resting on the exhaust pipe!

Phew, oh yeah the throttle cable had no play at all. Plus when I got the bike back it was idling at 2,000 rpm and I noticed that the fuel/air mix was shut down about half a turn, probably to allow for the extra air that they said was still leaking past the slides.

I've got the carbs out now and so I took a photo of what must be the 'pressed in' part that were referring to. They said it was just one of those things that doesn't happen very often but it has come loose and worn out. Please see the photos below and can anyone tell me if this really is what could have been the cause of all these problems.

The bike was working almost properly when I got it back so there's probably some merit in the leaking slide assembly diagnosis, I guess I'll know for certain when I get the new carbs in. I can see on these shots that there's some small round punch marks by the side of these pressed in parts.

[The Buddha]

Dude that looks normal, where is the part supposed to be and what did they "press in".
Sorry I smell a rat. I forgot the 01+ carb has no plastic slide guide like the 89-00.

Cool.
Buddha.

[The Buddha]

Do this, drop the slide back in without needle and don't even bother seating it. Stick your finger in the mouth and see if you can wiggle it side ways or back and forth and spray some wd40 and see if it is different, and slide up and down. Usually it starts feeling rough and gritty moving up/down.
Also post a pic of your slides. I find it had to beloeve a plastic slide got a metal press in insert loose.

Again - only gonna cause problems 1/2 to 3/4 throttle. Misfiring isn't a likely side effect there, but you will wear the needle fast, and if that is worn you can then misfire and crap out.

In fact in pre EFI GSXR 750's and 1100's that used to effectively destroy the needles long before it caused any other problems. The geniuses @ dynojet started making and selling the crap out of get this - Titanium needles. Yea, genius, drop a hard as fuccck needle in a brass emulsion tube where the aluminum needle was hitting and destroying itself. Instead of a $2 aluminum wire you can replace in 10 mins you're now wearing a unobtanium precision machined brass tube with threads and tiny holes in precise locations that will take you 3 hrs just to take apart and look at.

I better read your original post and your symptoms again. I seem to be forgetting what is the problem.

Cool.
Buddha.

[user11235813]

I gotta admit I'm finding it a bit strange but I'm willing to give the benefit of the doubt. I only got a description off them and it seems that the only thing I could see fits their description is that piece in the above photos. I can see that it's a separate bit that is fitted in, I don't even understand why it's a separate piece and not moulded as part of the body. It's the bit that cradles the wide side of the slide.

I'm going to take these photos down tomorrow and see if I can get some more explanation. However the problem did only occur above 1/4 throttle as you say from 1/2 to 3/4, if it got real bad I could rev the engine at WOT and it would come back to life for a while, so this does sound like the symptoms you described. And no it was never run with a dirty filter in fact the filters never even got very dirty.

Mine was a 2010 carb with Aussie plumbing. They did seem pretty clear about this part being loose

this is the new carb I bought https://www.ebay.com.au/itm/SUZUKI-GS-500-Late-Carby-Carburetor-Carbs-Throttle-bodies-EC-Only-3-000-kms-old/273041156444

Dude that looks normal, where is the part supposed to be and what did they "press in".
Sorry I smell a rat. I forgot the 01+ carb has no plastic slide guide like the 89-00.

Cool.
Buddha.

[user11235813]

@Buddha,

OK just saw you posted while I was posing. OK here's a photo of the slides, there's a bit of roughness on the semi circle side as you can see and there's not really much free play, maybe a millimetre side to side and back to front. But then apparently it's been pushed back into place, so I'm told.

I don't really have enough experience to be able to tell what is normal or not.





Strangely they leaned the air/fuel mixture a half turn on both carbs and pushed the idle up to 2000, but it was running well enough though so I guess it does seem to be something about the carbs. I'll be looking forward to seeing how the new ones differ. Could this bit of roughness on the slide cause this problem?

FWIW, when reassembling them last time they did feel smooth when I pushed them up and I also put the tiniest smear of sewing machine oil on them as lubrication because that is a very thin and light oil that doesn't gum up.

[The Buddha]

That doesn't look too bad on the slides. But if its rough, it will have trouble climbing RPM under load. If its rattling and loose in the guide, it will likely cause weird mixture anamolies as well as wear the needle and then really cause problems. That pressed in slide guide coming loose likely you can press back in and deal with it, or maybe use epoxy and glue it back to the body of the carb.
Cool.
Buddha.

[user11235813]

Well it's all pressed back in now supposedly, the end of the needles may look a bit worn, at least I'll have a new carb in a few days to compare it with. Will check back in then with a report. Could just be some astoundingly bad luck. This all begun a few days after I made a post about how well the bike has been running since I got it!

[The Buddha]

End of needles isn't where your rough spot on the slide would correspond to.
I still don't see where and how it came loose. Was it loose in the forward direction or did it lift itself out and you go prying that thing sometime
The 89-00 ones take a ton of work to get out, they are held in by the emulsion tubes. This guy probably is in just from sheer luck.
Cool.
Buddha.

[user11235813]

@Buddha, I gotta say the needles look fine, and as you say it all looks fine.

UPDATE:, while waiting for the new carbs I thought I may as well retune the bike and pull off all the vacuum plumbing and solenoid because it's all still on the new carbs anyway.

OK, I did all that and put the air fuel mix back to factory settings and then set the idle back to 1300, I've taken it for a short run and it's running fine, no hiccups at all. So this tells me that it's definitely not electrical and would have been this loose part that they found inside.

Here's some before and after pics with the vacuum bs removed. I now just have a vacuum hose going straight to the petcock. I connected to two vacuum inlets together on the white valves as that would be the same as plugging them up. Not that that should really matter because they are supposed to stay closed anyway unless they get vacuum. Same with the hose on top where they suck in air, I just sealed that with a bit of latex glove but again, if the valves don't open which they won't as they won't have any vacuum then it shouldn't even matter.

I will take it for a long fang tomorrow to see how it all goes. They warned me that the loose part which they say cannot be repaired! will likely come loose again in the future but I'll be putting the carbs on anyway and at the moment I'll basically be testing the performance with the vacuum plumbing removed.

[The Buddha]

That curved thing was loose - next time I crack my carbs open I'll have to look what that can do if it came loose.
Good luck with the ride, I'm sure it wont cause any more problems though.

Cool.
Buddha.

[user11235813]

Update:

I took it out for a fang on the freeway last night, perfect. Went to take it out today for a longer ride and wham, it's playing up again but in a way that looks to me very suspicious for an electrical problem. When the bike surges I expect the tach needle to swing a bit, but while it was doing that, it was also swinging wildly when the bike was not surging. And when it does this, it seems to be completely correlated to the apparent carb problem.

Maybe this is two separate problems that began together. Anyway I should have the new carb here today or tomorrow at the latest and I'll leave all the plumbing attached for the time being.

I mean how can the tach needle swinging wildly (at one point it was showing a 2000 when it should have been 4000) have anything to do with the carburettor if the bike is nor surging?

However I know nothing about the electrical workings of this bike but I believe the tach timing is electronic. Is there any way that whatever times the tach also times or supplies the spark?

This is beginning to appear to be two separate problems. Anyhoo once I get the new carb on then I will know for certain.

[user11235813]

New Update:

Got the new carbs today which was pretty good service. They look in top condition. There was a little bit of grittiness pushing the slides up but that seemed like just some dust so I cracked them open everything looked good wiped them out and put the tiniest smear of sewing machine oil on the slides. Float bowl gaskets were a bit dry but I had some new ones on hand so popped them in, put it all together with all the standard vacuum plumbing and it started up fine.

Took it for a bit of a local drive and if all feels good. Opened up the old carbs and I can't feel anything loose! Still it took 80kms before it started manifesting the problem so I'll take it for a 200km ride tomorrow and if it remains working then it would appear that it was the carbs even though they look fine and I can't find anything loose! Weird.

Here's a shot of the new pressed in bit...

[The Buddha]

They look ... same as your other pics.
Cool.
Buddha.

[user11235813]

@Buddha,

Yes they do. OK Went for a long ride yesterday and while on the whole it's running real nice after about 80kms I'm getting the surging and bouncing tach issue. Because the bike was almost not running at all when I took it in I'm suspecting that this is in fact two separate problems.

So now that I know this bouncing tach issue is nothing to do with the carbs, and really why would it be since the tacho is electronic.

I know it's not a faulty tach because the surging is *always* correlated to the tach needle bouncing, when the bike is running well then the tach needle is perfect.

I have a new CDI on the way because I got one for $25 and according to the wiring diagram the tacho and the ignition timing both go into this box so it seems a likely candidate.

I spoke to the service place again and they're really just guessing now like I am, but they suggested I take of the stator cover and see if that may be loose, then they suggested the timing mechanism under the right hand side, which sort of makes sense because I think, (not certain) that the tacho gets its signal directly from this bit.

Is there some way that I can use a multimeter to diagnose if there is a problem with the signal generator?

[gregjet]

If the tach needle is bouncing and the bike is surging you are looking at an electric problem. First guess ( as it looks like you have figured) is a bag ecu OR ECU ground....
IF a coil has a problem, it CAN ( not will) stuff up the tach signal as well as ( uses electronic coil conditions such as resistance, inductance, voltage rise etc etc) which will stuff up the timing.
ALSO check the reluctor and pickup. If either is loose it would do that. I have also seen intermittant did pickup coil problems on this forum.

[user11235813]

@gregjet,

That makes sense, nothing was loose under the ignition timing cover and everything is rust free. I have tested the coils with a multi meter and both were reading 5.8 Ω and 29K Ω factory workshop manual says 3—6Ω and 18K — 30K Ω So they're on the upper end of the limit, I don't know if that's a good thing or a bad thing! Is it good to be on the high side or does that indicate a borderline problem?

Should get the CDI black box in Monday.

[The Buddha]

In a coil high resistance is good. As the coils beging to wear, they don't really get thinner, they start to melt adjacent coils together and start shorting out in loops, start making more heat, more shorting etc etc, it may take forever to go from 6 to 5.8 but get to 5.6 in 1/2 that time, and to 5.4 in 1.2 that etc etc.

Bouncing tach - is that like bouncing B0081ES ... cos the guage cluster is the GS's B0081ES.

Yea you could have a trigger coil - under the right side round cover going bad. Can you get it to happen predicably ? Its usually temperature related. And will rapidly get worse, and get predictable and happen all the time @ a certain temp. Also I've had a failure where it has to get hot and the rpm has to drop and it will kick in. Like you can start it cold and ride local streets and in 5 mins it will lose a cyl. But if you start it cold and get on the highway and run WFO for 1hr, it will run fine till you slow down @ the exit. There it will lose that same cyl.

Cool.
Buddha.

[user11235813]

@Buddha,

I think you might be onto something there, now that the carb problem is sorted I'm left with this tiny problem. If you look at the photos earlier you can see where the new carbs have a single punch mark on the pressed in slide guide, and the one they worked on has an extra two punch marks so I have to believe that they were loose but the bike was unridable before, now it's pretty fine except for the occasional stumble.

As you said it appear to be more when it's warmed up and also it will occur during a corner and when I stop at lights and take off. Looks like this unit is replaced as a single item that plugs into the CDI. I guess if the new CDI doesn't fix this then I have no choice but to assume it is the coil in the ignition trigger. Good thing is that there are plenty of GS500's around here that are wrecking.

If I do change this unit is it just a matter of undoing the black screws [orange] and the ground bolt and taking it off and replacing with a new one. OR is there some trickiness involved about the exactly placement and rotation regarding the timing.

[The Buddha]

You also have to unscrew that green wire and follow it through the wiring loom and yes then its essentially pulling it off, putting on the new and routing the wire back and plugging it in.
Cool.
Srinath.

[user11235813]

OK. Latest update while waiting for CDI, I have unplugged the CDI and sprayed contact cleaner in the plug and I've also unplugged the Ignition timing plug and sprayed contact cleaner in that as well. So far after a 20 km ride all seems good carb is fine and there's no bouncing Bristols in sight ;¬0

I've notice a nick out of one of the CDI wires! hope it's nothing. See photo with pink square.

Also quick question on removing the CDI in case I have to. It looks like it's just held in with a rubber strap. Is this correct, do I just finagle it out of the rubber, is it just held in by the bits marked with pink and red arrows? Do I just lever the rubber up with a screwdriver and try to work it free of the rubber? Or is there some other better way (correct way) to do this.

thx.





Stop The Presses! Update: It looks like pulling the electrical plugs and spraying with contact cleaner has fixed this residual problem. Just came back from a 140km ride, slow and fast cruising, fast twisties in 3/4 gear, fast straight line and finishing with stop start traffic while fanging it off at the lights. All good not the slightest hiccup.