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1979 gs759L fuel problems please help!!

  • Thread starter Thread starter Anonymous
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Anonymous

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I have spent quite a while reading through old discussions, and i have read similar problems but can't seem to fine anything that helps me. I recently got a 1979 gs750L that had been in storage for ten years. The carbs have been recently rebuilt by someone who i am pretty confident knows his way around carbs very well. I bought a new air filter, changed the oil, and put on a new fuel petcock and the rebuilt carbs. It seems that gas is getting to the carbs, because when the valves are opened on the bottom, gas flows out (the float levels are set correctly). All four cylinders are getting spark. The problem is that i could get it to start (had a hard time doing so), but it only idles, and at that, very poorly. When i try to give it gas at all the engine dies, so i would assume that it is starving for gas. (when gas is poured into the cylinders the bike fires up). I am pretty sure that the carb lines are hooked up correcty . There are what i believe are two breathers that come out of the top of the carbs to the atmosphere, and a breather out of the bottom of each carb. The vacuum line and fuel line are hooked up (i believe correctly) to the new petcock.
I think that factory sync is set correctly, because it has not been messed with. Any help i could get would be greatly appreciated.

Ok i went out to try to get the bike running again. In experimenting, i took the 2 lines coming from the tops of the carbs and plugged them off, and the bike fired right up, so it makes me think its a vaccum problem.

Thanks a lot,
Steve Carlson
Duluth, MN
 
Re: 1979 gs759L fuel problems please help!!

I have a 79 750. Assuming you have the stock airbox and filter and stock exhaust pipes, set the fuel pilot screws (underneath the carb) to 1 1/4 turns out. Set the airscrews (on the side of the carb) to 1 3/4 turns out.
The float heights should be set to 24 mm. The 1/4" vacuum fitting on the petcock plugs into the vacuum fitting on the #3 carb. (carbs are numbered 1,2,3,4 left to right as sitting on the bike) All other vacuum fittings on the carbs are vented to atomsphere. The drain hoses that connect to the float bowls are vented to atomsphere.
A 1979 is a points and condensor ignition system. Have you checked points gap and ignition timing?
There is no "factory synch/vacuum balance" setting. Synching or balancing the carbs means to balance the intake velocity through the carbs for all four carbs. Balancing carbs requires a set of vacuum guages and a running engine.

Your points gap should be .014 and static timing for the 1,4 cylinders (left pointset) is the F1|. Static timing for the 2,3 cylinders is the right pointset and the F2|.

I will paste a copy of the points and timing setup proceedure to your PM if you need more explanation.

Earl



cafeteriadropout said:
I have spent quite a while reading through old discussions, and i have read similar problems but can't seem to fine anything that helps me. I recently got a 1979 gs750L that had been in storage for ten years. The carbs have been recently rebuilt by someone who i am pretty confident knows his way around carbs very well. I bought a new air filter, changed the oil, and put on a new fuel petcock and the rebuilt carbs. It seems that gas is getting to the carbs, because when the valves are opened on the bottom, gas flows out (the float levels are set correctly). All four cylinders are getting spark. The problem is that i could get it to start (had a hard time doing so), but it only idles, and at that, very poorly. When i try to give it gas at all the engine dies, so i would assume that it is starving for gas. (when gas is poured into the cylinders the bike fires up). I am pretty sure that the carb lines are hooked up correcty . There are what i believe are two breathers that come out of the top of the carbs to the atmosphere, and a breather out of the bottom of each carb. The vacuum line and fuel line are hooked up (i believe correctly) to the new petcock.
I think that factory sync is set correctly, because it has not been messed with. Any help i could get would be greatly appreciated.

Thanks a lot,
Steve Carlson
Duluth, MN
Click to expand...
 
earl is right on.follow his directions completly and you will most likly find your problem
 
earl, could you do me a hugefavor and send the timing and points info to me as well, it would be greatly appreiciated :D
 
Done, it should be inyour PM box now. :-)

Earl


hemp_1 said:
earl, could you do me a hugefavor and send the timing and points info to me as well, it would be greatly appreiciated :D
Click to expand...
 
earl, you are a gentleman, a scholar, and my hero!!!! thanx a ton!!!!! :D
 
hey thanks a lot earl. if i hadn't have just brought my bike down to my local suzuki shop for them to look at it, your advice would have probably helped me a lot (and saved me $150). But i do appreciate it.

Steve Carlson
 
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