GS500 help

zoomslide · June 12, 2006, 10:54:30 PM

My fellow GS500 friends. I'm new to the site and I'm in need of some help. I have a 1991 GS500 and I love it. The problem is this, when I start it up, it's fine, but after about 30 minutes, right when the bike gets nice and warm, it starts to bog down. It will stay running, but acts weak. ?? When I shut the bike down for 15 minutes or so, I can start it up, and it will repeat the same process. 30 minutes on 15 minutes off.
I've taken it to the only Suzuki dealer in town, and have asked many macanics for help. No one seems to know. I myself have done most of what I know how to do; Including testing the charging system, replaceing rectifier, stater and battery, so that leaves me with you guys. I'm sure that one of you out there have something that can help. Ya'll have way more knowledge about these bikes than I do, so send some my way.
Rob

ukchickenlover · June 12, 2006, 11:05:19 PM

I had a problem like this. My bike ran o.k then only on one cylinder then later both cylinders would cut out. I would not get a spark. I found it was due to the pulse generator coils.
I don't fully understand why this happened, I am guessing the coils expanded as they heated and made a bad connection. I changed the pulse generator coils for some 2nd hand ones I got off ebay which solved the problem.

Your problem may be different but if you can find some cheap coils off ebay maybe, it may solve the problem.

sledge · June 13, 2006, 12:01:32 AM

Thats a good explaination and could well be the root cause of the problem. I have had similar faults with coils and generators on other bikes over the years. As stated the coils get warm in operation and in addition to going open-circuit due to heat expansion and vibration the very thin covering of insulation that covers the wire can also break down and cause short circuits within the coil. It used to happen a lot on older bikes but as technology improved wound components became more reliable, but they are still not 100% reliable yet.

hmmmnz · June 13, 2006, 01:48:49 AM

im with the guys on coils, but this could also be that the bike is running rich. has the bike been rejetted??
id wind in the mixture screws, and wind them back out. the manual says 1 1/4 turns out but id go 1 1/2 to 2 screws out.
you'll know if the carbs have been fuct with if the little brass plug is missing that goes over your pilot screw, but even if it isnt id pull it off and check them. i have heard of them being wrong from the factory.
good luck

scratch · June 13, 2006, 08:57:04 AM

Welcome!

Is the choke still on?

LimaXray · June 13, 2006, 09:05:20 AM

What about valve clearances? Maybe they're a little tight

Recreational_Anxiety · June 13, 2006, 09:18:26 AM

I'd put my money on a rich running condition. Pull your plugs and check them. If they're black and sooty then you've got a rich mixture. When the engine is cold the excess fuel sticks to the cylinder walls and the engine will run fine, but when hot all the fuel is suspended and burned. If it bogs down at low speeds, check your float heights.

werase643 · June 13, 2006, 12:57:26 PM

ya wouldn't happen to have a nice tank bag on the bike would you?
with a rubber/neoprane bottom pad?

just a left field idea....

che mike · June 13, 2006, 01:04:10 PM

Quote from: werase643 on June 13, 2006, 12:57:26 PM
ya wouldn't happen to have a nice tank bag on the bike would you?
with a rubber/neoprane bottom pad?

just a left field idea....

werase, can you elaborate? i have a new tank bag, with a neoprene pad, and now you're making me paranoid!

Kerry · June 13, 2006, 02:13:31 PM

What werase643 means to say is that the tightly-fitting neoprene pad may prevent your fuel tank from "breathing" through the gas cap. With no air to replace the draining fuel, the fuel ... eventually ... stops ... draining..

Take a test ride without the tank bag and see if you get better results.

Egaeus · June 13, 2006, 03:29:17 PM

I'm not so sure che mike was getting bad results in the first place.

Kerry · June 13, 2006, 03:36:40 PM

Oops. My bad...

Egaeus · June 13, 2006, 03:40:31 PM

I've done the same thing. Lose track of who's asking what about where in the world is the thing on the bike. Just giving you a hard time.

Didn't have anything to add since you guys already used my ~~answer~~ guess (valve clearance).

che mike · June 13, 2006, 04:12:25 PM

Quote from: Kerry on June 13, 2006, 02:13:31 PM
What werase643 means to say is that the tightly-fitting neoprene pad may prevent your fuel tank from "breathing" through the gas cap. With no air to replace the draining fuel, the fuel ... eventually ... stops ... draining..

Take a test ride without the tank bag and see if you get better results.

ha ha, no, i haven't had problems with this; but it's an interesting thought. i should think it wouldn't happen due to the presence of the fuel tank overflow drain hose. it vents the inside of the fuel cap to the atmosphere, regardless of whether the gas cap is sealed shut by the rubber or not.

Kerry · June 13, 2006, 06:53:11 PM

Quote from: che mike on June 13, 2006, 04:12:25 PM[...]the fuel tank overflow drain hose [...] vents the inside of the fuel cap to the atmosphere, regardless of whether the gas cap is sealed shut by the rubber or not.

Not quite true, at least not on my pre-'01 bike.

The overflow hose connects to the bottom end of this tube that passes through the fuel tank. (Picture taken from the right side of the bike.)

The top end of the tube exits the tank to the left of the filler neck. The following photo was taken for a different purpose, but you can see the edge of the "hole" at 9:00, under the aluminum ring.

So ... the drain hose allows rain water or fuel from an "overfill" to drain harmlessly away from the bike, but it doesn't vent the tank itself in any way.

Do the '01+ models have a different setup?

che mike · June 14, 2006, 10:40:57 AM

"Do the '01+ models have a different setup?"

i wouldn't know, i ride an '89

so, explain to me again how a neoprene pad above the fuel tank would prevent venting of the tank? the gascap is not airtight, i assume. or gas-tight, since i've heard that if you drop your GS, gas will go around the filler cap and leak down the drain tube.

edit to clarify a bit: normally the fuel cap is not air tight and allows air to enter the tank. in the event that something (like a neoprene pad) seals off the top of the gas cap i would think the overflow vent would still allow air to enter the tank. since the pad would seal the top of the gas cap to the outside of the tank, but the overflow tube would still vent that shelf where overflow and rainwater collect, and air would then be able to travel from there around the gas-cap and into the tank.

has there been a confirmed case of the trouble with the neoprene thing happening? i'm still skeptical.

Kerry · June 14, 2006, 02:10:04 PM

Quote from: che mike on June 14, 2006, 10:40:57 AMhas there been a confirmed case of the trouble with the neoprene thing happening? i'm still skeptical.

Depends what you consider "confirmed" I guess. But check out this thread by werase643, the member who mentioned the neoprene pad several posts back.

(See especially the first post on the 1st page, and the last post on the 2nd page.)

Note that this problem and fix occurred on an SV650, so no ... I can't remember a confirmed case on the GS.

che mike · June 15, 2006, 10:52:23 AM

huh. i'll have to find an sv650 to inspect to see if its a similar design to the gs, but i'd guess they'd be pretty much the same. i wonder if it was just the pad that caused the suction, or the combination of pad + heavy tools, pressing down on the gas cap?

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GS500 help