I got my first bike, a 1994! I've wanted one for two years and finally got one...AND I didn't get kicked out of the house for buying it too! Double win!

But, the loss: I bought one for a few hundred bucks that had been sitting for five years. I took out the carbs, soaked/cleaned them, and put them back. Installed a new choke cable, changed the oil, and some other maintenence (why are all the bolts on this bike so prone to stripping and/or shearing off?!). Put a new battery in.

That's about the extent of my mechanical abilities. Now it starts and idles alright but the moment I touch the throttle, it instantly bogs down and dies. It can't take any load whatsoever. Once in a rare while I can get it to rev to higher RPMs and it'll hold, but then i let go of the throttle and it dies again. I have no idea what this could be, and I'm at wits end. It's been two months and the summer is almost over and I'm dying to ride...the thought of waiting another winter is horrifying.

Any ideas or suggestions? I'd like to at least have a direction to look at.

Carbs are jacked up, since it sat for 5 years, id buy a rebuild kit if you haven't already and replace all the rubbery bits.

sounds like its possibly not getting enough fuel.. did you touch the floats?

check for vacuum leaks too, around the carb boots mainly.



Cheesium bolts are known. I try to warn all new-comers about them, seems you learned the hard way. replacing the carb JIS screw heads bolts with allen bolts [hardware store like ACE has them] makes taking the bolts off a breeze in the future.

The simplest explanation would be that one or both of your main jets are clogged, so the bike won't run off idle.
If that is not the case, probably something like J_Walker is talking about. There are too many rubber bits to figure out what is leaking by trail and error. Just replace everything.

Also make sure the gas tank ins't rusty. If that is why the jets are clogged it will keep happening.

Also if you dunked the carbs with the rubber diaphragms in place, then you probably ruined the diaphragms and that's why it won't rev off idle. Easy enough to check. But basically a hole or tear or melted spot in the diaphragms (which is guaranteed if you got carb cleaner on them) will cause exactly the symptom you describe because the slide won't ever come up so the main jet stays closed. More air and no more fuel == super lean == bogs and stalls.

You need to pull the carbs and tear them all the way down, inspect, replace every single rubber part (o rings, diaphragms if they are not PERFECT), replace the pilot jet (probably clogged and way easier to replace, with a 40), clean everything, replace float needles, reset float height, replace intake boots and intake boot o-rings (almost guaranteed the intake boots are cracked if they are 23 years old and have been sitting), then when you get all this done, along with new spark plugs and a valve clearance check, provided the bike has decent compression, it should run.

Unfortunately that'll all cost you about 2x what you paid for the bike.

Before I dove into all of that I'd do a compression test just to make sure it's not a giant waste of money and time. Should be like 160psi both cylinders, if it's below about 140 on either cylinder then it'll have a hard time running right and below 120 psi on either cylinder will result in basically a limp-only condition.

Quote from: J_Walker on September 21, 2017, 10:01:55 AM
Carbs are jacked up, since it sat for 5 years, id buy a rebuild kit if you haven't already and replace all the rubbery bits.

sounds like its possibly not getting enough fuel.. did you touch the floats?

check for vacuum leaks too, around the carb boots mainly.



Cheesium bolts are known.

I had a small kit the last owner gave me but it only had the head gaskets, the big rubbery ones for the black caps. Nothing else. I'll look into getting a proper rebuild kit. Thankfully the carb itself is super clean looking which is what stops me from just buying a new carb.

I sprayed WD40 around the carb boot, I did not notice any changes in idle...and I did not touch the floats. A buddy drained each chamber for me once and we compared, they were about the same.

As for the JIS head screws...I'm hoping that they come out easy one last time and I'll replace them. If they're stuck, I think I'll set the whole bike on fire and walk away.

Quote from: Bluesmudge on September 21, 2017, 10:29:47 AM
The simplest explanation would be that one or both of your main jets are clogged, so the bike won't run off idle.

Also make sure the gas tank ins't rusty. If that is why the jets are clogged it will keep happening.

So...stupid question but how would I check if the main jets are clogged? I'm totally new to this and learning the mechanical aspect of this as I go...and the gas tank looks pretty clean inside, didn't see any rust.

Also, this may be useful: it only idles on choke, even after warming up for a few minutes. Take it off choke and it'll sputter and then make a pathetic dying sound...echoed by me as I watch....

Quote from: mr72 on September 21, 2017, 01:55:45 PM
Also if you dunked the carbs with the rubber diaphragms in place, then you probably ruined the diaphragms and that's why it won't rev off idle. Easy enough to check. But basically a hole or tear or melted spot in the diaphragms (which is guaranteed if you got carb cleaner on them) will cause exactly the symptom you describe because the slide won't ever come up so the main jet stays closed. More air and no more fuel == super lean == bogs and stalls.

You need to pull the carbs and tear them all the way down, inspect, replace every single rubber part (o rings, diaphragms if they are not PERFECT), replace the pilot jet (probably clogged and way easier to replace, with a 40), clean everything, replace float needles, reset float height, replace intake boots and intake boot o-rings (almost guaranteed the intake boots are cracked if they are 23 years old and have been sitting), then when you get all this done, along with new spark plugs and a valve clearance check, provided the bike has decent compression, it should run.

Unfortunately that'll all cost you about 2x what you paid for the bike.

Before I dove into all of that I'd do a compression test just to make sure it's not a giant waste of money and time. Should be like 160psi both cylinders, if it's below about 140 on either cylinder then it'll have a hard time running right and below 120 psi on either cylinder will result in basically a limp-only condition.

Ok, next time I pull the carbs out, I'll check for that. I put new rubber diaphragms in but maybe I got some of the old carb cleaner on them or something...or they were bad. I'll check!

What's the best place to get all of those parts and bits? And is replacing the main jet fairly straightforward? In general, is all that maintenance simple to figure out?

As for the money...well...that's unfortunate...but at this point, I may as well do it...not like anyone will but this bike for much anyways.

And compression check: how would I do that if I can't open the throttle up at all?

The bike won't be running during a compression check, the tester actually replaces a spark plug.

Unless you mean you physically can't open the throttle.

Quote from: Watcher on September 25, 2017, 04:51:40 PM
The bike won't be running during a compression check, the tester actually replaces a spark plug.

Unless you mean you physically can't open the throttle.

Oooo, got it. Ok, for some reason I thought it did. My bad! Thank you!

Quote from: AstroPenguin on September 25, 2017, 04:23:02 PM
Ok, next time I pull the carbs out, I'll check for that. I put new rubber diaphragms in but maybe I got some of the old carb cleaner on them or something...or they were bad. I'll check!

Yeah just remember rubber parts and carb cleaner don't mix. At all.

Quote
What's the best place to get all of those parts and bits? And is replacing the main jet fairly straightforward? In general, is all that maintenance simple to figure out?

You need to replace the PILOT jet most likely. But replacing either jet is easy and straightforward, go read the FAQ. There are good walk-thrus.

The carbs have two jets: pilot which runs idle up to maybe 1/4 throttle and maybe 4-5K rpms and then the main jet which runs all other conditions. The stock pilot jet is generally too small resulting in a very lean idle and hard running conditions, plus since it's only 0.375mm in diameter it's very easily clogged. Replace that with a #40 (0.40mm) pilot jet, one for each carb. Then you can set the idle mixture much better and you won'd wind up with hanging idle problems that plague these bikes.

The reason your bike won't rev off idle is most likely because the slides are not coming up and the needles are therefore staying down in the main jets. Now that I know you replaced the diaphragms, it's entirely possible something is wrong with the diaphragm installation, so I'd say you probably should open it up and redo that. While you are at it, make sure you don't lose the "little o-rings" that go under the vacuum ports on the top of the carbs. Easy to lose and forget to put back in. Also make sure those vacuum ports have covers on them and are airtight. The bike won't run right at all if this o-ring is missing or if the vacuum ports are not capped with an airtight cap.

Update!!

Thanks for all the feedback guys. I tore the carbs out again and started looking. I had replaced the o rings in the float bowls s month or so ago but in the process, I didn't adjust the floats. Also, I'm missing the tiny little o rings by the diaphragm vacuum nozzles. And lastly, I think my friend put the needle back in wrong. He used this order:
O ring, plastic disc, c clip, spring. But - and correct me if I'm wrong - I think the correct order is o ring, c clip, plastic disc, spring.
Right?

And I ordered #40 pilot jets. And a bunch of bolts to replace the stripped ones.

So floats, vacuum o rings, wrong needle setup, and new pilot jets. IF this doesn't fix my bike, I'm lighting it on fire.

Did I miss anything?

#40 pilot jet?! 

Quote from: J_Walker on October 01, 2017, 10:07:41 AM
#40 pilot jet?! 

I thought that was the pilot jet size that everyone recommended...like this blog:
https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html?m=1

Is that wrong? Should I just keep the stock jets?

40 is the right pilot jet for a '94 with the original carbs. Later model bike's had 3 circuit carbs and take a smaller pilot jet.

Any updates?

Quote from: emanuel_v19 on October 09, 2017, 03:35:03 AM
Any updates?

Hey guys, sorry yes! I've been traveling a lot lately and haven't had much down time. So here's the update:

My lovely pilot jets arrived and I decided to wait for my BikeBandit order to come in so I could just do everything at once. And since I've been out of town, I was ok waiting. Wellllll.....my order should have arrived last week. BB says it's still "in progress". I sent them an email asking about what the hold up is but have not heard back yet.

All in all, it's just another kink in the long road and it's already October. I just wanted to go around town once, that's all I ask. Is it too much to ask for?? Also a female friend requested a ride and well...it'd be nice to take her out.

Darn you Bike Bandit, darn youuuuuu!!!!!! But at the same time, I've been disappointed so many times already that this isn't even a surprise haha

Update!!!
If anyone is still reading hah.

Ok, today I rebuilt the carbs again. I put in both o rings for the vacuum nozzles that were missing. I replaced the pilot jets with #40s. I dremmeled out all the cheesium screws and replaced them with stainless steel ones. I put new gaskets on the carb boot intakes. And I rearranged the carb needle washers and rings to actually be in the right order. It was a good day!! Until I turned the ignition.

Uneven idle, dies instantly on any throttle. The uneven idle could be because I haven't synced the carbs yet, so ok. But what is up with the instant stall?? I can't give it any throttle whatsoever, and that isn't a sync related issue, right??

It's been this problem for the last month now and it's killing me. On the bright side, I've replaced a lot of parts that were going bad or needed replacing...but none of them have been the solution.

Suggestions? I'm getting pretty frustrated.

It's nothing to worry about, it could 1 of two things. your float height is still wonky. OR the idle mixture screw is just mis-adjusted

There is TWO idle mixture screws, one for each side. sometimes they get adjusted and one is way more open then the other, so basically forcing 1 cylinder to run on idle. best way is to take some feeler gauges, and look at the butterfly valves [the bass things inside the carb] on the back, look at one that looks more "open" by eye. take that one, and start sliding feeler gauges to get a good idea how "open" it is, now measure the other side. write both numbers [feeler gauge size] down.

Normally the more 'open' one is the correct amount for both sides, but when working with the unknown, I close the more open one, by half a turn, check the size, then adjust the other side [assuming two carbs here like the GS500] to the new size. go by feeler gauge not number of turns. this is MY method of adjusting both sides, assuming not an easily accessible adjustment screw.


if this doesn't improve anything, your floats are probably sitting too low. actually causing the valve to "close up" shop sooner. The metal tab on the floats, holding the floats how they sit in the carb. should be pushed only just slightly upward, about the thickness of a fingernail. from the completely flat/level position.




Make sure the return spring for your choke is correct.

Quote from: J_Walker on November 02, 2017, 08:45:54 PM
It's nothing to worry about, it could 1 of two things. your float height is still wonky. OR the idle mixture screw is just mis-adjusted

I'll take a look at the mixture screws! As for the floats, I didn't actually do anything with them now that I think of it. I just put them back in and moved on. In fact, I've never messed with the float heights....I recall one tab sits higher than the other, the other is about level. Is there a good walkthrough with pictures for setting that?

Also, my return spring for my choke cable is a little small, so I had to force it. It doesn't bend very badly but enough...why is that bad?

And last, what is that 3rd picture showing exactly?

Sorry, I'm learning all of this as I go so I have tons of questions. And thank you for the help!!

That not so obvious idle adjustment screw is actually the synch screw.
Cool.
Buddha.