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I have a couple of problems with a 1980 GS550 that I could use a little advice on.
This bike has 16000 miles on it and has not been run for at least a few years. The OEM ignition had lost the spark output on the #2 and #3 cylinders which probably was the reason it was parked.
The bike has had the following maintenance done so far:
New Dyna S Ignition
Complete Carb. teardown and cleanup including the new O ring kit. As per the docs on this and the basscliffs site(They were not really in that bad a shape other that a little varnish)
Valve clearances where checked and all were in spec.
New plugs
Rebuilt kit on the fuel petcock
Sealed the airbox
Problem 1: I put everything back together and fuel would not flow into the carburetors until I pulled off one end of the crossover line that ties the vent ports of the 1-2 carbs to the vent port on the 3-4 carbs. At this point I could start the bike and run it. If I put the crossover line back on I lose flow to the carbs again. This sounds like there is a float bowl vent port plugged somewhere but I don’t know where it would be. It will still only run if the crossover tube is pulled.
Problem 2: The #2 and the #4 cylinders do not want to fire at Idle. This is after a carb sync and balance. Both of them will pick up at around 1500 to 2000 RPM or at idle if I pull the choke out .
Stuff that has been checked to try and track down the problem:
Checked for air leaks
Switched plugs from the good to the bad cylinders
Pulled the carbs down again and verified all ports and jets clear, settings ok and same size jets in all the carbs and that CV slides were free and not sticking
Checked the float levels with a drilled a drain plug and with clear tubing attached
Verified Battery charge and good voltage to the new Dyna S unit
Verified solid engine and frame grounds
The initial cold compression check on the engine was not very good with a high of around 90 on #1 and #3 and a high of around 60 to 65 on #2 and #4. This was a roughly a 5 second test with the throttle wide open all the plugs pulled. Subsequent tests after 5 minutes of run time showed about the same values. Surprisingly a cylinder leak down test was less than 3 PSI loss at 100 PSI test pressure on all the cylinders. (I’m still scratching my head on that one). Pouring a little oil into the cylinders brought the compression test up to +175 on all the cylinders so there is some wear of the rings/walls but the valves appear to be sealing well.
The fact that I have ignition in #2 and #4 only while choked suggests that there is not enough fuel in the mixture going into the non firing cylinders. I suppose I could still have some carb issues that I have not found but now I’m leaning toward the compression is being too low for the spark to trigger the mixture at low RPM values.
Any thoughts or advice on these issues would be appreciated
This bike has 16000 miles on it and has not been run for at least a few years. The OEM ignition had lost the spark output on the #2 and #3 cylinders which probably was the reason it was parked.
The bike has had the following maintenance done so far:
New Dyna S Ignition
Complete Carb. teardown and cleanup including the new O ring kit. As per the docs on this and the basscliffs site(They were not really in that bad a shape other that a little varnish)
Valve clearances where checked and all were in spec.
New plugs
Rebuilt kit on the fuel petcock
Sealed the airbox
Problem 1: I put everything back together and fuel would not flow into the carburetors until I pulled off one end of the crossover line that ties the vent ports of the 1-2 carbs to the vent port on the 3-4 carbs. At this point I could start the bike and run it. If I put the crossover line back on I lose flow to the carbs again. This sounds like there is a float bowl vent port plugged somewhere but I don’t know where it would be. It will still only run if the crossover tube is pulled.
Problem 2: The #2 and the #4 cylinders do not want to fire at Idle. This is after a carb sync and balance. Both of them will pick up at around 1500 to 2000 RPM or at idle if I pull the choke out .
Stuff that has been checked to try and track down the problem:
Checked for air leaks
Switched plugs from the good to the bad cylinders
Pulled the carbs down again and verified all ports and jets clear, settings ok and same size jets in all the carbs and that CV slides were free and not sticking
Checked the float levels with a drilled a drain plug and with clear tubing attached
Verified Battery charge and good voltage to the new Dyna S unit
Verified solid engine and frame grounds
The initial cold compression check on the engine was not very good with a high of around 90 on #1 and #3 and a high of around 60 to 65 on #2 and #4. This was a roughly a 5 second test with the throttle wide open all the plugs pulled. Subsequent tests after 5 minutes of run time showed about the same values. Surprisingly a cylinder leak down test was less than 3 PSI loss at 100 PSI test pressure on all the cylinders. (I’m still scratching my head on that one). Pouring a little oil into the cylinders brought the compression test up to +175 on all the cylinders so there is some wear of the rings/walls but the valves appear to be sealing well.
The fact that I have ignition in #2 and #4 only while choked suggests that there is not enough fuel in the mixture going into the non firing cylinders. I suppose I could still have some carb issues that I have not found but now I’m leaning toward the compression is being too low for the spark to trigger the mixture at low RPM values.
Any thoughts or advice on these issues would be appreciated
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