Dead cylinder

[Guest]

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? :-k

.

 

[Guest]

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

 

[Guest]

What all was included in the "everything" that was replaced? :-k

.

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.?

 

[Guest]

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

 

[Guest]

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

 

[Guest]

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:

 

[Guest]

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.

 

[Guest]

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

 

[Cipher]

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

Hey my bikes run fine after I work on them.

 

[Guest]

I really appreciate all the attempts to help, i truely do. But i can see im on my own on this one still. I’ve been battling this thing off and on for probably five years. I’ve been told all the usual things and at this point ive done them all. If it’s the carbs it’s a setting not neglect. Christ knows I’ve inspected every molecule that they’re made of. The only thing I can say is I wasn’t able to re-check the clip settings on the needles because I have misplaced my long reach circlip pliers. Oh how I hate that stinkin design.
im half temped to take it back to stock jetting despite the pods which haven’t been run anyway during this troubleshooting.
Heck maybe I have a mouse stuck in that header!

I have had this bike for close to twenty years. Before the pods it had an airbox that was held together with silicone and ran good but was always temperamental. I’m finding myself working on it again after losing my last house three years ago and finally getting settled in my new home workshop. Every time I get into it i get sidetracked and it sits. Its had a lit of these problems because of the sitting. That’s why I’m full on into it this time. Maybe the engine has just finally gotten too old?

anyway, here’s a list of what’s been and checked
1.wire harness gone through, resoldered, new weatherpack plugs, heatshrinked
2. carbs completely disassembled, soaked, inspected, oringed
3. plugs swapped around, buying new tomorrow if I can find someone open that sells ngk
4. plug wires between 2&3 swapped
5. all wires spark equally
6. pickup coils were bent and repaired (no difference)
7. Valve clearance all in the mid-range of spec.
8. All cylinders get fuel, spark and compression
9. #1,3,4 100psi ( seems low) but are firing
10. #2 130psi not firing
11. Carb slides all move up when throttled. #2 seems to not go as high further testing required
12. petcock vacuum is not getting gas from leaky petcock
13. floats are set to 22.4mm (I measured to top of rounded part not higher squared off portion on pivot end
14. 37.5 pilot jet
15. 24 main dynojet
16. iirr needle clip in 3rd notch down inspection required when i find pliers
17. have not tried hotter plug yet
add more later if I remember more- it starts to get jumbled up in the memory which is why i come here to find clarity again and hopefully someone with more brains than me.

 

[Guest]

Hey my bikes run fine after I work on them.

i meant no disrespect btw just a chuckle

i have seven motorcycles all of different ages and types that run great. I have one that never runs great. No one touches my bikes but me. This used to be my exwifes basket case. As frustrating as this bike is, it’s more fun than she ever was. I should just get rid of it but i love the engines sound and want to enjoy that again.

 

[storm 64]

i meant no disrespect btw just a chuckle

i have seven motorcycles all of different ages and types that run great. I have one that never runs great. No one touches my bikes but me. This used to be my exwifes basket case. As frustrating as this bike is, it?s more fun than she ever was. I should just get rid of it but i love the engines sound and want to enjoy that again.

Is there any way you can get the ex-wife to lift the curse she put on it? I'm guessing no...

 

[allojohn]

Sounds like a carb problem.

+1 .