78 GS 1000 help please...

[Anonymous]

Hi guys, I have just put my 78 1000 back together after going through the carbs. It started right off but will only run with the choke on, and when I try to give it gas it just dies....I didn't put anything new or different in the carbs, just cleaned them up good....another question I have is that it was apart for so long I can't remember where those 3 small hoses that come off the top of the carbs go..or if they hook to anything at all....I know the bottom ones are just for overflow of the float bowls...but does one of the top one's go to the extra port on the gas valve on the tank....please help me...oh yeah I also put a new set of points in it also...thanks guys....

itching to ride.....

[Anonymous]

the 3rd carb line is for fuelvalve vacuum the others or vents, did you mess with the air screws?

[Jay B]

Lines

Two of them are vent hoses and the third provides the vacuum to open your petcock. If its not hooked up it wont open and you wont get any fuel.

[Anonymous]

Thanks for the info, I tried putting the hose that comes off the 3rd carb on the fuel tank valve and still having no luck. It still just dies when I try to take the choke off or give it gas as I back the choke off. I didn't do anything to the carbs when I had them off, just cleaned them good and put them back on. I starts fine but will not run without the choke. You did say the other two small hoses off carb 2 & 4 are just vents and don't hook to anything right. And what about the fitting that comes off the fuel gage does one of the hoses go to it...I'm really lost guys it run ok until I cleaned all the carbs....appreciate anymore info....thanks....

[argonsagas]

Since the bike starts, you probably have the the hose on the fuel valve, unless you have the valve on Prime. If it is on prime, then the fuel will run even when the engine is not running, otherwise it will not come out of the tank unless the engine is running as it needs vacuum to open the valve.

The fuel guage should have a yellow and a black/yellow wire, not a hose.


There is a section on this site called In the Garage. It will give you a pictorial display of how to disassemble a carb and show the various parts.

I am not sure that I have the same carb on my 82 1100 as you have on yours, but I had a similar problem (not as severe) that was caused by blocked pilot jets on two carbs. It takes very little to screw them up.

On my carbs you drain the fuel, then remove the bowls, pull out a small black plug with your fingers, and the jet is under the screw you now see.

Remove the screw and washer and take out the jet carefully. The mentioned site instructions will tell you to get a single bristle from a metal brush and put it in a pencil eraser to hold it. Hold the jet up to the light and see if it is clean or blocked. (You should see a bit of light) If blocked, use that new tool to open it, by carefully pushing the bristle through the hole and into the jet. Then put the nozzle of a carb cleaning spray against the opening on the tip of the jet and blow it clear. Give a full second to blow clean.

Blowing it clear is important as if you don't then the debris will come right back and clog the hole again, because it probably only fell inside the jet when you pushed it clear.

Install an in-line fuel filter to avoid this problem in the future.

You might also remove the tops of the carbs and check that the diaphragms are in place correctly and are working properly, with no tears. There is a little tab on the edge of the diaphragm and it has to go into a matching slot on the casting.

[Anonymous]

Thanks Ron, I'll see what I can do, the only thing that has me confused is why it will run so good wtih the choke on. I can rev up and everything to 4 or 5000 rpm and it will stay running. And the gas valve is in the on position, I do know about the prime position and how it works. So I guess I'll just keep working on it. And I'll check out that Garage section you mentioned also.....happy ridin......

[SqDancerLynn1]

Rons ideas are good but unless your 78 GS bike has been modified it should have the slide type carbs, i would take them apart (float bowls & jets) again and reclean them,paying close attention to jets and double check your float level.
If i understand your question about the gas valve?? there is an overflow cover on the fuel gauge sending unit for an overflow hose.