"New" bike won't run! Help!

[SmithvilleFlats]

Hey, new to the site, just bought a '93 GS 500. It starts and runs.....kind of.
It'll turn over a couple times, maybe start, and then die.
The seller said it needed new carburetors, but i cant imagine why. I would think they would just need calibration .
I'd like to fix it myself, if possible, before paying $60 an hour for someone else to do it.
Any ideas? Help me out!

[beRto]

Hey, new to the site, just bought a '93 GS 500. It starts and runs.....kind of.
It'll turn over a couple times, maybe start, and then die.
The seller said it needed new carburetors, but i cant imagine why. I would think they would just need calibration .
I'd like to fix it myself, if possible, before paying $60 an hour for someone else to do it.
Any ideas? Help me out!

Are you using the choke to start the bike (it's the lever by the left grip)?

If it's been sitting awhile, the bike will likely need new sparkplugs and fresh fuel at a minimum. The battery may also be weak/dead. Most likely, you will have to remove, disassemble, and clean the carburetors.

I'm not sure why new carbs would be required unless the previous owner did something to damage them? Best thing to do is take them off and have a look inside.

Keep us posted and feel free to ask any questions.

[04gs]

I have never replaced carbs on a motorcycle.  I can almost guarantee that there is varnish inside the pilot jets.  just take them apart and remove the jets.  clean them with a strong carb cleaner.  make sure you can see through the jet after wards.  good luck!!!!

[lewismug]

I have never replaced carbs on a motorcycle.  I can almost guarantee that there is varnish inside the pilot jets.  just take them apart and remove the jets.  clean them with a strong carb cleaner.  make sure you can see through the jet after wards.  good luck!!!!

+1,000

There are plenty of write-ups on this site that deal with cleaning carbs.

[ben2go]

Here's a link to cleaning.

http://gstwin.com/carb_work.htm

Carb float height check.

http://www.bbburma.net/FloatHeight.htm

Carb balancing.

http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/5CarbSync

Another problem that comes up with older bikes is the vacuum operated petcock.Vacuum operation can be eliminated.I do the conversion for $10 includes return shipping.
Here's a couple links to remedy this.

http://gstwins.com/gsboard/index.php?topic=19363.0

http://gstwins.com/gsboard/index.php?topic=36958.0

[SmithvilleFlats]

Thanks!
I got the carbs off, and i can see why someone would just replace them.
The owner had the choke cable jb welded to the carb body, and it looks like he patched it in one spot.
I got them cleaned up so they should be good to go.
I also picked up a fuel filter because there was some grime coming out of the tank, so I'll have to clean that up too.
I'm guessing there will be some vacuum problems, also. The carbs' intake gaskets were a little cracked, but we'll see.

Some people might say it's a little rough, I just say it's got character!

Cant wait to get this thing on the road!

[beRto]

Thanks!
I got the carbs off, and i can see why someone would just replace them.
The owner had the choke cable jb welded to the carb body, and it looks like he patched it in one spot.
I got them cleaned up so they should be good to go.
I also picked up a fuel filter because there was some grime coming out of the tank, so I'll have to clean that up too.
I'm guessing there will be some vacuum problems, also. The carbs' intake gaskets were a little cracked, but we'll see.

Some people might say it's a little rough, I just say it's got character!

Cant wait to get this thing on the road!

pics?

Tank grime, like rust? Or sludge, like water on the bottom? Either way, in addition to the fuel filter, you probably want to get rid of the old gas and rinse out the tank with some fresh stuff.

[ben2go]

Post a pic of the broken choke area on the carb.Someone may have a good carb body or slide.

[SmithvilleFlats]

Just patched up the carb and put it back on. It should work fine. I'll take pics next time I take it off.

New issue: I took the spark plugs out and they were coated with black oil, so I'm guessing there's a leaky piston ring or valve somewhere.
How common is this? What will it take to fix this?
Thanks

[kml.krk]

Just patched up the carb and put it back on. It should work fine. I'll take pics next time I take it off.

New issue: I took the spark plugs out and they were coated with black oil, so I'm guessing there's a leaky piston ring or valve somewhere.
How common is this? What will it take to fix this?
Thanks

it MAY just be that Previous Owner changed the main jets and used too large ones. The plugs would be then covered with black substance. If this is the case you will be too rich on fuel and you need to change the jets to smaller ones. WAIT for others opinion though, I'm not pro so I may be wrong
good luck and I hope to see the pics soon!
Kamel

[beRto]

Just patched up the carb and put it back on. It should work fine. I'll take pics next time I take it off.

New issue: I took the spark plugs out and they were coated with black oil, so I'm guessing there's a leaky piston ring or valve somewhere.
How common is this? What will it take to fix this?
Thanks

The following chart shows spark plug colours and conditions:


Where do you fit?

If the spark plug is in fact oily, a compression test will help to determine the condition of the rings/valves.

[SmithvilleFlats]

Definitely oil fouling on both plugs.

[beRto]

Definitely oil fouling on both plugs.

Yuck.

This thread explains how to use a cylinder compression test to determine if the problem is the piston rings or the valves:
http://gstwins.com/gsboard/index.php?topic=38986.msg438007#msg438007

More info on compression tests:
http://gstwins.com/gsboard/index.php?topic=40110.0

[SmithvilleFlats]

Well I went out and got my compression tester and it turns out it doesnt fit the smaller spark plug hole on bikes, so I'm still not sure what the problem there is.

After perusing the pages of this site, it's become clear that my fuel system is not at all stock.
The fuel runs from the gas tank here...


...directly into the carbs here.


Weird?

[beRto]

The previous owner probably had fuel starvation problems and solved them by using that by removing the frame-mounted petcock and replacing it with an "aftermarket" petcock (the red and black one). The current setup seems to draw fuel from the reserve outlet on the tank. What is the other outlet connect to?

Use the info on Kerry's website to verify that the fuel hose routing is correct:
http://www.bbburma.net/FuelHoseRouting.htm

[SmithvilleFlats]

The second outlet on the tank's petcock is plugged. Also, the vacuum hose to the left carb does not appear to be there.

[beRto]

The second outlet on the tank's petcock is plugged. Also, the vacuum hose to the left carb does not appear to be there.

With this setup, the vacuum hose to the left carb is not necessary. The vacuum hose is normally used to actuate the frame-mounted petcock, allowing fuel to flow only when the engine is running.
http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Petcock

However, the vacuum port on the left carb should be plugged. Otherwise, the carb will suck a lot of excess air and will run lean.

[beRto]

Well I went out and got my compression tester and it turns out it doesnt fit the smaller spark plug hole on bikes, so I'm still not sure what the problem there is.

Sorry, I forgot to comment on this before: the compression tester usually has a screw-on adapter that will allow you to use it in the smaller plug. If your tester didn't come with this piece, it may be available separately.

[ben2go]

If you have or can get a stock petcock convert it to non vacuum.I do this mod for $10 that includes return shipping.
http://gstwins.com/gsboard/index.php?topic=19363.0

Or you can get a cheap replacement.
http://gstwins.com/gsboard/index.php?topic=36958.0

[SmithvilleFlats]

So am I going to have to replace the petcock or is this setup workable?