Dead cylinder

[EDGECRUSHER]

I’m trying to diagnose a dead #2 on my 83 gs750es. It has pods and was jetted but never ran well. I just realized #2 is cold so I tested everything i can think of. Valve clearance is spot on. I had an issue with my pickup coils being bent but fixing that didn’t make a difference. I swapped the plug wire between 2 and 3 with no effect. It is sparking the plug fine. The plug has gas on it when i checked its condition and gap. The confusing thing is the compression. I get 100 psi on every cylinder except 2 which is 130 psi. I’m not sure if im hearing things but when i have the guage on 2 and turn it over sometimes I hear a “ ting” sound. When I try to make it do it again I can’t, so I never get a good idea whats making the sound. I cant account for the high compression and the fact it wont fire with gas and spark. Is there a way just 2 can be out of time? I’m lost. I just rebuilt the carbs, the RIGHT WAY!, and replaced everything and dipped them - the whole 9 yards. I figured I better do that to rule out flooding in that cylinder. Please help.

[rphillips]

It's rare, but a plug can fire outside the cylinder, but under compression, not fire. swap the #1 & #2 plugs, just to be sure the #2 plug is firing under compression. won't take but a minute. If #1 quits firing, it's the plug.

[Steve]

... I just rebuilt the carbs, the RIGHT WAY!, and replaced everything and dipped them - the whole 9 yards. ...

What all was included in the "everything" that was replaced?

.

[EDGECRUSHER]

It's rare, but a plug can fire outside the cylinder, but under compression, not fire. swap the #1 & #2 plugs, just to be sure the #2 plug is firing under compression. won't take but a minute. If #1 quits firing, it's the plug.

did this with no effect

[EDGECRUSHER]

What all was included in the "everything" that was replaced?

.

every o-ring, hard parts were soaked and cleaned like i said. I had dynojet #130 mains in and i swapped them for dynojet #124’s. No other changes. I have new intake boot orings but my testing did not show any vacuum leaks there, so I’m holding onto them for now.

[tom203]

#2 cylinder.....of course, you’ve ruled out petcock dribbling down its vacuum line.

“ The plug has gas on it when i checked its condition and gap.”

[EDGECRUSHER]

Yeah. I don’t understand how anyone can have a tank on and off as much as you do during this sort of thing and not notice that

[EDGECRUSHER]

What are the chances the exhaust valves aren’t opening even though I measured clearance several times?

[EDGECRUSHER]

I suppose this weekend I’ll need to pop the top off again and just confirm valves moving and timing is on. Doesn’t seem to be a lot to timing this engine. I don’t see any adjustments at the pickups...
I just really think this is something with the engine more than anything

[Gorminrider]

What are the chances the exhaust valves aren’t opening even though I measured clearance several times?

on my 650 i can see the valves opening through the plug holes. A finger over the plug hole will also inform as to compression and suction.

[bobgroger]

The pilot jet is the most common culprit. Under the Rubber plug next to the main jet. It has a VERY small hole in the end that can plug up in just a few weeks with Ethanol gas. You need a length of 30 gauge solid wire (.25mm) to clean it out. Hold it up to a light and make sure you can see through it. You DID put new rubber plugs in, right? You need them. I rebuilt a set of carbs in October and ran the bowls out of gas but didn't drain them. In February it wouldn't start and had 3 of 4 pilot jets plugged, and this in the # 1 and 2 bowls:

[EDGECRUSHER]

I popped the top and the valves aren’t sticking. They have to be shutting all the way because I have compression. Ive heard the gasket can go bad between cylinders and cause a cylinder to read high but I’d imagine the other cylinder would show some kind of loss as well.

[Cipher]

Did this thing run fine prior to the work you did.
Or at least fire all four cyls?

How is 100 on 3 and 130 on 1 high compression?

You swapped plugs swap plug caps
or move coils.

[Nessism]

Sounds like a carb problem.

[EDGECRUSHER]

Did this thing run fine prior to the work you did.
Or at least fire all four cyls?

How is 100 on 3 and 130 on 1 high compression?

You swapped plugs swap plug caps
or move coils.

next time i see you post a question ill ask it back to you too lol