Good Spark but Won't Start

[flazwy]

79 GS750L had been sitting for a while after a move. Changed out jets for new altitude. Fresh gas. Bike started like a champ.

a week later- will not start.-weak sparks. Replaced battery- no luck. Tested each plug agaist engine and had good spark. New Battery has 12.7 volts off trickle charger.
Engine turns over when cranked, even tried to kick-it.
Don't know if conections need to be cleaned or....

[-o<

 

[robertbarr]

Open the carb drain screws. If you get roughly a bowl full of gas each time, you have ignition or compression problems. Otherwise, you have no fuel to the carbs.

Next step -- compression test.

 

[Guest]

Try priming the float bowls with the prime position on the petcock.

 

[SPARKSS]

79 GS750L had been sitting for a while after a move. Changed out jets for new altitude. Fresh gas. Bike started like a champ.

a week later- will not start.-weak sparks. Replaced battery- no luck. Tested each plug agaist engine and had good spark. New Battery has 12.7 volts off trickle charger.
Engine turns over when cranked, even tried to kick-it.
Don't know if conections need to be cleaned or....

[-o<

A little conflicting info here regarding whether you have good spark or not - This should be a nice blue spark that you can hear snap as it flashes across the gap.
You say it started like a champ.......did you drive it at this point? Did it work well at this time? One week will not affect fresh gasoline. Is there any other history not mentioned (assuming it ran good as asked first.....but with other work done in the interim)? Have you checked the crankcase for fuel dilution (oil will smell of raw fuel and a sample will light to a flame easily). If you've had fuel flooding during that week, you may very well now have low compression in one or more cylinders - if this is determined, change the oil, plugs if fuel fouled (black wet) and add a little squirt of engine oil to each (or affected) cylinders while the spark plug is out (this often helps regain compression temporarily allowing a start)......and of course, fix the cause of the flooding.

 

[flazwy]

Thanks for the info.

When it started before, I didn't ride it, needed to do some mantanence before going on the road- chain, breaks etc. The sparks were bright white/blue with the new battery.

I drained the bowles(one bowl was dry) and it started up. I was able to ride it to the gas station and fill up. It didn't run great, but ran. I think it was starving for fuel as the fuel line had a too much of a bend. I had recently replaced the petcock, and apparently they don't make the stock for the 79 GS750L. I had to settle for something that fit the holes, but had the output on the side( not the back as the original) I haven't had a chance to fix the bend yet and take it for a good ride. I also need to change the oil and will check for gas smell.
It's been little used the last few years( ~200 miles /year) and hoped to use it more now that I'm out of a cold climate.

A little conflicting info here regarding whether you have good spark or not - This should be a nice blue spark that you can hear snap as it flashes across the gap.
You say it started like a champ.......did you drive it at this point? Did it work well at this time? One week will not affect fresh gasoline. Is there any other history not mentioned (assuming it ran good as asked first.....but with other work done in the interim)? Have you checked the crankcase for fuel dilution (oil will smell of raw fuel and a sample will light to a flame easily). If you've had fuel flooding during that week, you may very well now have low compression in one or more cylinders - if this is determined, change the oil, plugs if fuel fouled (black wet) and add a little squirt of engine oil to each (or affected) cylinders while the spark plug is out (this often helps regain compression temporarily allowing a start)......and of course, fix the cause of the flooding.