1983 gs750es sounds like a Harley and random start

[Eidollan]

Need help figuring out what's going on... Just 2 weeks ago I had my cylinder head re threaded for the spark plug, mechanic put back the engine and it ran, had the bike picked up since I wasn't home, after a week ran th bike and it sounds exactly like a Harley weird battery is also weak, charged the battery overnight, I got busy so I wasn't able to check on my bike again for a week. Got a chance to check on the bike and it won't start it would crank, there's a strong spark, gas is flowing from the carb and good compression but bike won't start, cranked it a few more times and I heared it trying to start gave it gas and it ran, again sounds like a Harley, it ran for a minute and died and won't start again. After a couple tries it starts for a few seconds and dies again. I notice something on the carbs 3 and 4 when I removed the filter and tried to start it would blow out gas... My suspicion is the timing was set wrong. Any thoughts on this?

[phydeauxmutt]

There is no way to set the timing, but it's easy enough to swap a couple of spark plug wires.

In a stock situation, the left coil will fire plugs 1 and 4, the right coil will fire plugs 2 and 3.

Keep in mind that "left" and "right" are referenced as you are sitting on the bike, ready to ride.

[Eidollan]

There is no way to set the timing, but it's easy enough to swap a couple of spark plug wires.

In a stock situation, the left coil will fire plugs 1 and 4, the right coil will fire plugs 2 and 3.

Keep in mind that "left" and "right" are referenced as you are sitting on the bike, ready to ride.

Did that nothing happened, won't even try to start, I hear the pistons moving no combustion.

[tom203]

So your mechanic had head off ?? If yes, then did he use a new head gasket and torque it properly?

“After a couple tries it starts for a few seconds and dies again. I notice something on the carbs 3 and 4 when I removed the filter and tried to start it would blow out gas..”

might be blown head gasket between 3 and 4......get/borrow a compression tester and explore.

[Eidollan]

So your mechanic had head off ?? If yes, then did he use a new head gasket and torque it properly?

“After a couple tries it starts for a few seconds and dies again. I notice something on the carbs 3 and 4 when I removed the filter and tried to start it would blow out gas..”

might be blown head gasket between 3 and 4......get/borrow a compression tester and explore.

Yes he did remove the head and yes he did use a new head gasket.

That's one more weird thing I borrow a compression tester and it showed 130psi on 3 and 4... This is the very first time I've seen this, it's like when the piston is on the intake stroke exhaust valve is open then on the compression stroke the intake valve is open.

[phydeauxmutt]

Normal logic would say "your 'mechanic' needs to fix his mistake".

Common wisdom says "don't let him anywhere near your bike".

You will have to remove the valve cover to observe cam movement and valve timing. First, make sure the cams are in their proper place(s) and turned the right way around.

One final thought: did your 'mechanic' also change the BASE gasket? If not, he should have.

[Eidollan]

Normal logic would say "your 'mechanic' needs to fix his mistake".

Common wisdom says "don't let him anywhere near your bike".

You will have to remove the valve cover to observe cam movement and valve timing. First, make sure the cams are in their proper place(s) and turned the right way around.

One final thought: did your 'mechanic' also change the BASE gasket? If not, he should have.

Oh definitely that mechanic is never touching my bike again, I would rather pay again than him doing it again, I'm bringing my bike to my trusted mechanic I could already hear him say wtf did that mechanic do. I'm just hoping no valve is bent.