Right cylinder won't fire, running out of ideas...

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Fellas,

Have read the other threads on this problem and tried some different things, but am still having trouble. Here's where I'm at:

-Engine just rebuilt, 6th over pistons, lapped valves, etc.
-Have converted to Pamco ignition
-Running linked BS38 carbs
-Currently have straight pipes on and no airfilters

Left cylinder fires up with choke and a couple strong kicks.

Right cylinder has compression, spark looks good.

I've cleaned the right carb 3 times and seems like all passages and jets are clear.

Also tried messing with the sync screw but did not have any luck. I did notice when turning clockwise the rpms for the running left cylinder would slow.

Would sincerely appreciate any help you guys could provide. I'm a bit confused as to how to diagnose further because the Pamco instructions say to always run with both spark plugs hooked up.

Thanks in advance...

xsjohn

Could try a bit of starting fluid on the right and see what happens.........

xsjohn

Retiredgentleman

If you want to look at the spark, you can remove the plug to view the spark, but just be sure to keep both plug bodies grounded. I use a spare plug with an alligator clip that I connect to an engine fin.

Might be good to check a few basics. A compression test on both cylinders just to confirm all is normal. Do you have normal battery voltage?

Do you have a new ignition coil and leads, or are you using an older coil and leads?

Are you confident that the carbs were properly cleaned? Those pilot jets have very small orifices. Did you shoot carb cleaner through the pilot circuit, and check with air flow that the passage ways are clear?

What year are the BS38 carbs? That would give you a starting point for the air/fuel mixture screw setting.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

thanks guys. I REALLY appreciate the ideas.

John,

thanks for the notion on the starter fluid, I'll give that a shot. wasn't sure if these motors like that sort of thing or not.

RG-

I did the carb cleaner/blow air routine and was getting stuff through the pilot passages well. I've got a new coil and leads installed and the spark looks good. Tho I might use your idea on the ground wire to pull my left side plug and focus on the right.

I'll double check the year on my carbs and go back through the old threads to see 'bout a mixture setting. Will my current lack of air filters throw that off to bad?

pamcopete

cscarroll

Check that all 4 magnets are in place in the PAMCO rotor. If one is missing, you will still see spark on both cylinders due to the wasted spark scheme of the system, but only one cylinder would be getting spark on the compression stroke.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Pete,

Thanks, checked that and we're good.

-C

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

One other thought on this, has anyone ever tried moving the left carb to the right in hopes of isolating the problem to the carb itself and not something else?

-C

kyle1911

I like John's idea, that's where I would go first. It cuts to the chase. Just be cautious with the starting fluid. It is snappy stuff, if you use too much, or get a backfire. Just a spritz, with the throtte open (Reach in with a finger, and lift the Vac slide.) then kick it over, and see what happens. If it fires, you are on track for carb problems. A long shot, but it has been known to work. Start the engine, and put your hand over the dead cylinder's carb inlet. It's a very crude tactic, but the vacuum has been known to get things to fire sometimes. Is the dead cylinder's plug wet with fuel? Speaking of plugs, are you running new spark plugs? I've had plenty of used plugs over the years, that looked clean, and sparked outside the engine, but not under compression. That will drive you nuts! The carb moving idea would work, but a huge hassle, that you should be able to avoid, with these tests.

Retiredgentleman

To get that right cylinder to fire, check the basics. Compression test, battery voltage, check timing with a strobe light.

I know nothing about tuning with no air filters and straight pipes, except that it will be very difficult to tune. You'll be playing with main jet sizes, slide clip position and pilot jet sizes/mixture screw.

pamcopete

cscarroll

Well, some simple things:

1. Remove carbs and check that throttle openings are the same. Use a feeler gauge. Can also be done on the bike.
2. If you have vacuum barbs, is one of them open?
3. Replace spark plugs.
4. Drain fuel from both bowls. Same amount?
5. Check compression.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Pete-

Thanks for the feeler gauge idea, and I'll recheck the vacuum barbs. If I disconnect one spark plug to isolate my right cylinder, will it cause problems with your system?

Kyle and RG- thanks for the ideas I'll give them a whirl, go back through the basics and see where I end up...

pamcopete

cscarroll

Well, that's possible, but what is more likely is that you will short out the coil internally because a dual output coil does not have an internal ground reference, so with only one plug connected, the internal high voltage will find a ground, usually by arcing to the primary winding.

So, you can connect the wire to a plug grounded to the engine. RG has a test plug that he uses that has a convenient wire attached to the plug for that purpose. Take a look at his post above.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Pete,

Quite right. RGs test plug is the way to go.

Thanks. Partly I just wanted to understand what was going on in your system with "always hook up two plugs" rule.

For future reference, do I risk burning up a coil if I foul a plug?

xjwmx

cscarroll wrote:

For future reference, do I risk burning up a coil if I foul a plug?

Interesting question!

pamcopete · Last edited by pamcopete on April 23, 2009, 7:32 pm; edited 1 time in total

cscarroll

No, because a fouled plug is basically shorted through the carbon buidup. A shorted plug will not damage the coil because there is still a path to ground, through the carbon.

Also, this is not just a peculiarity of the PAMCO system. Any ignition system, including a dual lobe points system, that uses a dual output coil has this limitation.

Now, that's not to say that the coil will always self destruct with one plug disconnected, but there is a high risk that it will. It's also possible that the coil will arc internally, but not form a permanent path to the primary. The trick is to catch it before it has a chance to form a path from the carbonization of the insulation on those very fine wires in the secondary winding or to burn a hole in the insulation.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Pete,

Thanks that makes perfect sense.

I've said it before, I'll say it again, your system has been a breeze to setup and use. So far, it has been the least of my worries.

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

Hey guys.

Thanks for all the help. Got the right cylinder running good. Looks like the ol' "put your hand over the carb" trick worked. I'll be doing some other checking to make sure everything is up a going well.

thanks again for the tips. they helped alot.

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