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Road trouble

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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I have a 79 GS750L that will idle just fine,give immediate throttle response, and run just great---until I put it in gear and try to ride. Then it will miss, sputter, and act like the gas has to catch-up to the throttle. What do I need to do?
 
Re: Road trouble

kevin mannion said:
I have a 79 GS750L that will idle just fine,give immediate throttle response, and run just great---until I put it in gear and try to ride. Then it will miss, sputter, and act like the gas has to catch-up to the throttle. What do I need to do?
Click to expand...
does it happen in second gear or other gears as well??
 
Plugs 1-2-4 are dry-sooty black and I clean them often. I have tried to adjust the air-screws and replaced the air filter with a k&n unit. Because of the running(riding) problem there has been alot of "idle" time on this bike and not alot of riding.
 
kevin mannion said:
Plugs 1-2-4 are dry-sooty black and I clean them often. I have tried to adjust the air-screws and replaced the air filter with a k&n unit. Because of the running(riding) problem there has been alot of "idle" time on this bike and not alot of riding.
Click to expand...
Did you lose plug #3 and ir is starting to sound like your spark is bad
 
one remote possibility, a bad ground! with the bike still and in neutral it gets enough ground through the transmission gears, but moving the oil film on the gears prevent it from grounding through them, check the point where the ground wires attach to the frame, clean and make sure they are tight.
I have seen this once before, it is rare but happens
 
I checked and cleaned all of the plugs today. All of them were sparking just fine, and plug 3 is showing signs of use. I simply assumed the air screw was set just right for the #3 carb.
 
Listen to leon. this smells lie an electrical problem to me. Just a feeling
after that the carb freaks will have to jump in
 
I think in your '79 you have standard ignition....what you are describing could be caused either by bad condensors or just maybe by wrongly spaced points or even a weak coil...but the latter would mean TWO weak coils, so I would look elsewhere.

As you said it runs fine with no load, but poorly under load, by all means check the points, but I would lean towards replacing the condensors.

(Note....it does not matter when you installed them....reality is that sometimes condensors last minutes, instead of months or years.)
 
I replaced both of the coils(a month ago),and this morning both condensors and both points. I checked and rechecked the points gap and the setting is fine. I checked the ground wire(at the battery case I assume, it was the only ground wire I found) and it seemed to be fine as well. Some more tinkering with the air screws as well as the idle seemed to help some but the onset of night will delay anymore play until tomorrow.
 
Taking a tip from another post I let the bike run a few minutes then checked the exhaust and found I could fully grab the third pipe while the other three were too hot to touch. What do I need to do? The plug is firing and just to check I swapped it out with another and the third pipe was still cool while the fourth ran hot after the plug swap.
 
kevin mannion said:
Taking a tip from another post I let the bike run a few minutes then checked the exhaust and found I could fully grab the third pipe while the other three were too hot to touch. What do I need to do? The plug is firing and just to check I swapped it out with another and the third pipe was still cool while the fourth ran hot after the plug swap.
Click to expand...
seems like you have ruled out the electrical theory. Now see if the carb to the cold cylinder is getting fuel or if possibly it is clogged internally and also if the float level may be stopping gas from getting to that carb. Here is a thought. If it is not firing number three then that plug should be wet if it is getting gas.
 
Is there a way to check the fuel intake on the carb without having to remove the whole bank and disassemble the whole unit? I hope!
 
Dead Cylinder

Dead Cylinder

Don't overlook the possibility that the #3 plug wire boot could be jumping fire to the head. This is extremely hard to see in the daylight. I had the same deal with 1 cold cylinder and 3 hot. I found it after starting it after dark one night.
 
Bad Plug Wire

Bad Plug Wire

Start the bike in a dark place like in a garage with the lights out during the day or anywhere after dark and look for a spark jumping from the spark plug wire to the cylinder head. The reason it is hard to see in daylight is that it may be pale blue or pale yellow so the brightness makes it not visible.
 
If this were the case, would the plug for that cylinder be wet with raw gas? My plug is coming out dry and I think that the "signs of use" may well have been the spray type carb cleaner I used and not gasoline. If there is a way I can check the carbs' fuel intake without removing the whole bank I'd love to hear about it! Also I've been told that my throttle linkage could also be the culprit, any input here would be appreciated as well.
 
open the drain plug on the float bowl and see if anything comes out but if that plug is dry then it sure sounds like a fuel problem
if the other cylinders are getting gas what is it that causes you to want to check the fuel flow from the tank???
 
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