GS850: 1 dead cyl/brown foamy fluid from crank vent (upd)

[Dave_A]

Ok, more 850 issues...

The last problem I had dealt with fuel venting out the carb vents....

While I'm waiting for my carb repair set to come, I pulled my plugs & saw that 3 were wet/black (gas fouled -> rich) and one was wet/brown.

I thought this might be due to the prior owner re-jetting, so I'd try putting pods back on (it was set up for UNI foam pods, and I came into an extra set of 4) to see if that corrected the fuel venting issue.

Well, the bike idles with the pods (won't rev up though -> I'm starting to think the prior owner didn't re-jet again), but it also only runs on 3 cyls. #2 does not fire (exhaust is cold when the other 3 are hot). Also, it's blowing brown bubbly crap from the crankcase breather (which it didn't do before with the airbox on).

All cyls have good compression, but #2 was the one with the brownish-wet spark plug...

Any ideas on the dead cyl (plug wire)?

Also, any ideas on the frothy brown crap blowing out the top of the motor (no, the bike wasn't left on prime, and the petcock does not leak. There should be NO gas in the crank)???

Also, what is the firing order for a GS? Does it fire 2 cyls simultaniously (eg 1&4-2&3) , or 1-3-2-4 like a car?

[SqDancerLynn1]

Tipical problem with #2 is from the petcock. if the petcock diaphram leaks it will flood the #2 cylinder with fuel. So check the vacuum line from the petcock for evidance of fuel--- The petcock will still shut off like it is supposed to do

[Anonymous]

I don't much of anything, but from reading another post I do know that the gs fires 1-2-3-4.

Drew

[Detman101]

After getting this stupid drop on cylinder two now after replacing the petcock diaphragm I am bought a Pingel Petcock this morning.
Should be here by tuesday then I can finally get my bike running on all 4 reliably again and not burning my eyes at stoplights.

Stupid oem rubber condom petcock!
BEGONE!!!!
:twisted:
Dm of mD

[Dave_A]

All of this happens with the fuel tank REMOVED, running on gas from the float bowls/feed line.

The petcock does not leak, I've stored the tank for a few days with gas in it, off the bike, and no leakage occurrs.

Also, WRT the splatter of brown goo, there is enough pressure in the valve-cover that when I plugged the breather with my thumb, the brown stuff was splattered about 6ft back from pressure buildup after I took my thumb off...

This did not happen with the airbox on (or there would have been crap coming from the breather vent in the bottom of the box)...

SHOULD THERE BE SIGNIFICANT PRESSURE COMING FROM THE CRANK BREATHER VENT???

ALSO
My reason for asking about firing order is that my CDI blew a capacitor. I replaced the cap with a larger one (since the little blue/black caps in the CDI aren't available anymore, I put a 1uF unit from radioshack in there instead) & the bike runs, but #2 doesn't fire.

The issue is that I don't know why #2 isn't firing. If there is a separate signal to fire it (which seems odd, as #2 & #3 are fired by the same coil), it could be the CDI unit 'fix' didn't quite work right...

Or it could be that #2 wasn't firing before & I didn't notice. I suspect this, since the #2 plug was fouled by unburnt gas (that is the correct indication for a light-brown wet plug, right?) prior to the CDI issue.

So I have compression & fuel, that would seem to indicate no spark...

How do I check this... Swap #2 & #3 plug wires? Run the engine with the plug out & grounded against the head to look for spark?

[Dave_A]

btt, anything else?

[Detman101]

I would have tried swapping the sparkplug wires from 2&3 with the ones from 1&4 to check first.

Then I would have taken each sparkplug cap off and tested it visually with a spare sparkplug to see if the sparkplug fired on each sparkplug wire.

Dm of mD

[saaz]

Blow back through the vent indicates some pressure past the rings, which should not be there. It could be due to the cylinder not firing, as this would not seal the rings on that piston.

My very recent experince with plug caps is that they may test ok cold but fail when warm. Two ignition coils later.... I would just change the plug caps to make sure if you do not know how olde they are. At least then you have a good reference point.

The brown gunk seems to me to indicate oil gunk build up, which means short trips and/or oil changes not dome often enough.

[Dave_A]

Blow back through the vent indicates some pressure past the rings, which should not be there. It could be due to the cylinder not firing, as this would not seal the rings on that piston.

My very recent experince with plug caps is that they may test ok cold but fail when warm. Two ignition coils later.... I would just change the plug caps to make sure if you do not know how olde they are. At least then you have a good reference point.

The brown gunk seems to me to indicate oil gunk build up, which means short trips and/or oil changes not dome often enough.

1) It's had one ~20mi trip to get brought home, and the rest of the time just run briefly in my garage & around town as I work on it...

2) Plug CAPS? They come off??? It looks to me like they're part of the plugwires.... If no, how do you get them off & on without wrecking the wires?

3) Is there a specific multimeter test (resistance/ohms?) that will tell me if my #2 plug wire or plug cap has gone kaput?

[Dave_A]

Solved

Well, it turned out to be a carb issue...

To solve a previous problem with gas coming out the vent tubes, I rebuilt the carbs (new fuel & air jets, replacement pilot plugs, new needle valve assembly)...

With the re-built carbs, all four cyls fire again...

As for the crap coming out the breather, it turns out that I had a crankcase full of gas... I'm guessing that #2 was flooded out so badly that gas was draining past the rings...

Oh well, it works now, quite well...