Can't get the motor running on a GS450 1981

[Guest]

Hey

I have a GS450EX from 1981 that i bought a couple of months ago. No knowledge of its history but i dont think it's been started for quite some time. Had to replace the starter relay, ignition coil and the igniter to get ignition. Tried starting it yesterday but didn't get it to run. I got a couple of revs with it when I sprayed starter gas into the air filter but then it dies instantly. It doesnt seem like it's is getting fuel into the cylinders. I took off the spark plugs after a while and they were completely dry, when I guess they should of become sour after so much time choking.
I am quite a novice when it comes to motorcycles and I am not quite sure how the tank connects to the carbs, since it came disassembled.
The large hose coming from the pet cock I got connected to a connection in the middle of the carbs. The small hose (which I guess is vacuum) o got connected to a nipple on the left side of the left carburetor. When I had a fuel filter connected on the large hose, it doesn't get filled up, which I guess it needs to. I tried connect the vacuum and disconnect the large hose and I could see some fuel poring out so it seems to create some kind of vacuum at least.

What are your suggestions? Carburator disassembly and clean up?

[Brendan W]

First I would set the fuel cock to prime and open the float bowl drains to see if any fuel was getting in. Then I would remove the fuel cock from the tank and see if the filter is blocked.

[dbursell]

I dont have a prime unfortunately. But when i suck on the vacuum hose fuel comes out of the tank. Opened the float bowl and fuel is poring out.

[Brendan W]

Plan B then. Bike of that age and unknown history has more than likely got blockages in the carburettor fuel and air passages. Disassembly and clean up as you said.
Keep you eyes open for something stupidly obvious like is the choke control actually moving anything.

[jdvorchak]

Once you get the carbs off and apart I'm sure you'll see a lot of gunk in the bottom of the float bowls. Check for "how to clean carbs" type of videos and documents to see how to thoroughly clean the carbs, jets and idle circuits. It helps if you have a Chem dip, like Berrymans. It will require you to completely disassemble the carbs to get them really clean. Just cleaning the float bowl will do nothing to help.

[tkent02]

You have Prime, unless someone switched the petcock. These a little screw on the petcock, loosen it and fuel is flowing.

[Larry D]

http://gsarchive.bwringer.com/cbsaunders/gs/gs450_carb_cleaning_guide.pdf

[JRHemmen]

The vacuum created by the Pistons pulls open a diaphragm in the petcock which allows gas to flow out of it, this keeps gas from free flowing when the bike is off (that's what prime does). There's a chance your filter is blocked or your petcock is gummed up, but more than likely it's the carbs. Disassembly and cleaning certainly won't hurt anything, there's a great guide on here for cleaning our specific carbs. You can also take apart the petcock and soak that too, just make sure you don't soak anything with rubber on it (i.e. the diaphragm).

Finally, I'd make sure your fuel line is as direct and short as possible. My bike wouldn't start, I cut about 3 inches off of the fuel line and it started right up. It's gravity fed and any unnecessary bends will cause issues. You could also try having somebody hold the tank up and see if it ignites. That's how I got mine started the first time.

*edit*

the link Larry posted is the same guide I was talking about. If you clean the carbs, absolutely follow that procedure.

[Blueline]

Whilst we are discussing two cylinder GS bikes, and carbs, has anyone got an idea what size the vacuum hose is supposed to be? Mine is only a 250 though, not a 450.