No fire on #4

[stng_96]

Ok folks, I have gotten my 80 GS1000 running, but questionably. Did the carbs all the way as suggested here, with 40 pilots and 110 mains. Got new intake boot rings, good airbox and filter, new plugs, bench sync and it runs decent. With my brand new morgan carbtune hooked up, I get good even readings on 1 and 3, 2 is a little bit lower reading on idle, no reading to mention on revs, and 4 does nothing. I am getting a nice blue arc when I ground the plug and crank it over from four, but still no fire. Put the new plugs in yesterday, and ran it for a short period, pulled the plug back out, and it has nothing on it, not anything at all. I do keep hearing a psssh of air from that side of the motor, every seconnd or so, and it burps when I rev it. Any suggestions?

[Steve]

..., and 4 does nothing.

This needs a bit more of an explaination, if you don't mind.

Are you saying that #4 does not move the carbtune at all, or that it goes to one place, then does nothing as you blip the throttle, or ...?

If you are getting no vacuum reading on #4, the first thing I would do is swap the vacuum leads for 3 and 4 to make sure the Carbtune is not lying to you. If #4 is not giving you any vacuum reading, you have a serious leak somewhere. It's remotely possible that it is open so far that the engine is running on only the one cylinder, but that does not match your description of how it is running.

Another possibility is mis-adjusted valves. Have you checked valve clearances? They should have been checked before doing a carb sync. If you do a perfect carb sync, then go back and change a couple of shims, you will have to re-sync the carbs, because the cylinders will be drawing a different amount of air through the same opening in the carb, yielding a different vacuum reading.

Worst-possible case: you might have a burnt valve, which can not seal up to the head. Aa compression test would confirm that.

.

[stng_96]

It is not moving the carbtune at all on number four, Ill switch those ones around and see if that helps anything. there is some condensation that built up in the carbtune on the number four testing tube, mean anything to you?

[BassCliff]

Hi,

Can you do a compression test?

When you hook up the #3 tube of the Carbtune to cylinder #4, does it pull a vacuum? Is the vacuum port from carb #2 plugged?


Thank you for your indulgence,

BassCliff

[stng_96]

Bass, are you talking about the vacuum port for the fuel petcock, or the carbtune adapter?

[Steve]

It is not moving the carbtune at all on number four, Ill switch those ones around and see if that helps anything. there is some condensation that built up in the carbtune on the number four testing tube, mean anything to you?

As I suggested earlier, switch the tubes from #3&4.

If the rod in Carbtune #3, which is connected to engine cylinder #4, does not move, your problem is in the engine.

If Carbtune rod #4 still does not move, your problem is with the Carbtune.

.

[BassCliff]

Hi,

Bass, are you talking about the vacuum port for the fuel petcock?

Yes. This is assuming that you have the main fuel tank off and you are using an auxiliary tank. If so, plug the vacuum line from the #2 carb that usually connects to the petcock.

Here's my aux tank and a golf tee stuck in the vacuum line.



Forgive me if I state the obvious.


Thank you for your indulgence,

BassCliff

[stng_96]

Bass that's about what mine looks like too, and now for the bad news......#4 cylinder builds 120 cranking psi......grrrr

[Steve]

Bass that's about what mine looks like too, and now for the bad news......#4 cylinder builds 120 cranking psi......grrrr

OK, so it builds cranking pressure.

Have you swapped the vacuum lines yet to determine if it might be your Carbtune?

.

[stng_96]

Steve yes I am sorry I didn't mention that before, but yes, swapped and it stayed with that cylinder. Isn't 120 pretty darn low, #1 makes 155?

[Steve]

Steve yes I am sorry I didn't mention that before, but yes, swapped and it stayed with that cylinder.

So you are saying that when you swapped the vacuum hoses, #3 in the Carbtune did not move?

Did you move the hoses at the engine or on the gauge?

If you moved them at the gauge, you might have a plugged hose.

.

[stng_96]

I moved the hoses at the engine. Previously the far right tube attached to my number four cylinder was showing no readings, maybe a little blip here and there, and after I switched the number four cylinder to the 2 tube from the right it showed the same thing, also with condensation in the tube. Carbtune is functioning properly.