No intake pressure on #2 cylinder.

[Dragonslayer]

During Vogel I used Stevew's carb tune to do a carb sync. When I hooked up the carb tune I found that my #2 cylinder was showing no pressure whatsoever. I was able to sync the remaning three cylinders. Now I'm faced with figuring out why I have no intake pressure on the #2 cylinder.

 

Does anyone have any ideas what to look for?

[MiCarl]

What the synchronizer measure is the drop in pressure in the intake. I assume you mean that there is no measurable pressure drop there (at least nothing that shows on the carb tune).

 

You either have a massive intake leak or the butterfly on that carburetor is way more open than the others. Or maybe a ruined valve, but your question implies you're riding it ok.

 

The CarbTune seems to measure pressure in CM Hg. If the reading on the 3 carburetors you have synced is more than 25CM Hg then you're likely way out in your adjustment. Those three are way too far closed, #2 is way far too open, and #2 is doing all the work.

 

I assume it idles? If so, fire it up and spray starting fluid around the #2 carburetor and it's intake boot. If the bike doesn't rev up it isn't an air leak.

 

If there is no air leak put the sync gauges back on it. Start turning the sync screws on the other 3 carburetors so their pressure goes up (the columns on the gauge will get shorter). Try to keep them pretty much even as you go down. You will probably have to turn the idle screw up as you go.

 

Eventually you'll see the level on #2 rise, when all four are the same you're synced.

[wes0778]

I remember listening to it, and I think we decided that cylinder was dead. have you checked to see if that exhaust pipe was hot?

[rjg1985]

Have you had the valve clearence checked?

[skydoc_17]

Hey Bob,

Did you by chance stick a tooth pick in the Vacuum port of the #2 Cylinder?

Sometimes these ports get plugged up and need to be cleaned. Carb. Cleaner and the little red extension work well for this. Did you try one of the other lines on the Carbtune to make sure that it isn't the Carbtune malfunctioning?

Just a thought,

Earl

[Dragonslayer]

Have you had the valve clearence checked?

No I have never checked the valve clearence,. That repair is one that I have always dreaded having to do because it seems so complicated. I was hopeing against all hopes that it might turn out to be something else.

[Dragonslayer]

Hey Bob,

Did you by chance stick a tooth pick in the Vacuum port of the #2 Cylinder?

Sometimes these ports get plugged up and need to be cleaned. Carb. Cleaner and the little red extension work well for this. Did you try one of the other lines on the Carbtune to make sure that it isn't the Carbtune malfunctioning?

Just a thought,

Earl

Good thought, I'll check that.

[Dragonslayer]

I remember listening to it, and I think we decided that cylinder was dead. have you checked to see if that exhaust pipe was hot?

It was getting hot but not at the same rate as the other three. Remember that I had developed and exhaust leak while returning from the dragon. Is it possible that a change in exhaust pressure might effect the intake pressure?

[Dragonslayer]

What the synchronizer measure is the drop in pressure in the intake. I assume you mean that there is no measurable pressure drop there (at least nothing that shows on the carb tune). I mean that the mercury on the #2 cylinder was not registering at all no matter what adjustments were made to sync the other three carbs.

 

You either have a massive intake leak or the butterfly on that carburetor is way more open than the others. Or maybe a ruined valve, but your question implies you're riding it ok.

 

The CarbTune seems to measure pressure in CM Hg. If the reading on the 3 carburetors you have synced is more than 25CM Hg then you're likely way out in your adjustment. Those three are way too far closed, #2 is way far too open, and #2 is doing all the work.

 

I assume it idles? If so, fire it up and spray starting fluid around the #2 carburetor and it's intake boot. If the bike doesn't rev up it isn't an air leak. I'll check this

 

If there is no air leak put the sync gauges back on it. Start turning the sync screws on the other 3 carburetors so their pressure goes up (the columns on the gauge will get shorter). Try to keep them pretty much even as you go down. You will probably have to turn the idle screw up as you go.

 

Eventually you'll see the level on #2 rise, when all four are the same you're synced. I tried this while doing the sync and never got any rise at all on #2[/QUOTE] Could this condition be a result of electrical current from the coils through the TCI being low or non existant?

[MasterGuns]

My money is on a vacuum leak. The best way I've found to find a vacuum leak is to use a can of starting fluid (ether). With the bike idling, start spraying a little around areas that might be suspect. Where the rubber manifold bolts (mates) to the head is one. Another is where the carbs sit in the manifolds. If you spray the ether even close to a vacuum leak, the ether will be sucked in and the idle will get noticeably higher. I recently had the same problem but from what you describe; not as bad. Anyway, give it a shot. Never know until you check.

[MiCarl]

Could this condition be a result of electrical current from the coils through the TCI being low or non existant?

 

Nope.

 

It's not an exhaust leak either. If you don't find a vacuum leak (and the nipple isn't plugged) check the compression on that cylinder.

[rjg1985]

I have a miss on the #2 cylinder of my 85. I did a compression test on it and it was low about 65 psi. I the did a leak down test and had air leaking out the exhaust. I took it in and had the valve clearance checked, but only 2 intake valves needed adlustment and not on the #2 cylinder. I am to the point of pulling the head and replacing the valves. The bike runs really good even with a weak cylinder, but I want it to 100%.

[83VR3711]

I had the same issue with my #2 carb on my 83. I checked everything I could possibly think of, including the electrical system. It turned out the Screw that held the main nozzle on the slide assy had come off. I opened up the carbs and put it back together and it ran like a champ. Just an idea.

 

--83VR3711

[Dragonslayer]

I had the same issue with my #2 carb on my 83. I checked everything I could possibly think of, including the electrical system. It turned out the Screw that held the main nozzle (Do You Mean needle?)on the slide assy had come off. I opened up the carbs and put it back together and it ran like a champ. Just an idea.

 

--83VR3711

Just a little confused did you mean needle instead of nozzle?

[83VR3711]

Just a little confused did you mean needle instead of nozzle?

 

I am sorry for the confusion, I was refering to #26 and #28 carb section in parts catalog. Page B6. I hope this helps.

[Dragonslayer]

Any other ideas

[Dano]

I would go with the stopped up tube theory. You could open up the air box and visually check that the butterfly on #2 is closed. If the piston is in there and it's going up and down and the valves are opening and closing (doesn't need to be all the way, but it helps!) then you should be getting some kind of reading on the synch tool. Try a different channel on the tool just to rule that out.

You are measuring the vacuum created by the air rushing past the tube that you hookup to. This is created by the vacuum the piston creates when it moves downward. Ergo, even if both intake and exhaust valves are completely open, you should still get some kind of reading there.

 

Just my wandering thoughts,

 

Dano