Dry spark plugs

I am trying to resolve a starting issue with my 1971 750 Commando. Just fitted Pazon ignition and Pazon HT dual coil.
Static timed it as per instructions. Good sparks on kickstarting with plugs out.
But no matter how many times I kickstart it, even with say half throttle, the spark plugs are bone dry and no smell of petrol.
I have twin concentrics and both bowls flood on ticklers ok. I have had these carbs apart and blown through all the jets.
Inlet valves close properly and engine compression is good on both barrels.
Surely the plugs will become slightly wet?
Any clues?

Air filters fitted? Maybe try a squirt of easystart or similar to see if it fires

Did you have it running before changing the ign?
Did you change anything else at the same time?
What’s the age / condition of the carbs?
Standard or Premier?
Chokes or no chokes?
Remember that blowing air through passageways proves only that they are not 100% blocked. It doesn’t tell you if they’re partially blocked, flowing correctly, etc, etc.

Tickle them more.

And only open the throttle a teeny weeny bit.

It's usually the pilot jet bushes clogged with symptoms you describe

I wouldn't touch the throttle while kicking in this scenario...

Fast Eddie said:

Did you have it running before changing the ign?
Did you change anything else at the same time?
What’s the age / condition of the carbs?
Standard or Premier?
Chokes or no chokes?
Remember that blowing air through passageways proves only that they are not 100% blocked. It doesn’t tell you if they’re partially blocked, flowing correctly, etc, etc.

Click to expand...

The bike after a couple of years of sweet running, started misfiring after a very high throttle opening in third gear. (oops)
At that time (October 20) I could start it a few times and it ran clean for about 20 secs then it died and finally would not start at all. I decided at the same time to replace the old Boyer system as I had planned that anyway. Standard carbs, no choke fitted. I did wonder whether the camshaft has 'moved' , perhaps a key shear on one of the timing chain sprockets?

bluuman said:

The bike after a couple of years of sweet running, started misfiring after a very high throttle opening in third gear. (oops)
At that time (October 20) I could start it a few times and it ran clean for about 20 secs then it died and finally would not start at all. I decided at the same time to replace the old Boyer system as I had planned that anyway. Standard carbs, no choke fitted. I did wonder whether the camshaft has 'moved' , perhaps a key shear on one of the timing chain sprockets?

Click to expand...

Did it backfire through the exhaust? I had a bent exhaust valve once, compression felt ok, but it misfired/popped/banged when we fired it up.

I was convinced it was ignition at the time, swapped my spare one on and it did the same

Sounds to me like you had a fuel delivery problem well before you swapped ignition systems.

You say the ticklers flood normally, but apparently petrol is not getting into the manifolds.
Try this .... squirt a little petrol directly into each carb with the throttles open. If all is well with the ignition system the engine should start and run for a few seconds. If it does start and run, rule out ignition, and look for blockage in the carbs.

If the engine does not fire, try starting fluid, a 1 second burst in each carb. Then if no fire, check ignition.

You say you have good spark with plugs removed, but that is no guarantee you have spark under compression. Get one of those in-line testers that are inserted between your high tension lead and the spark plug. The quality of the flash indicates the spark quality.

Slick

When I got my 71 commando, It had been sitting for 30 years. I rebuilt the entire bike and installed a Pazon ignition and dual coil. I got it to start but it would run only on 1 cylinder. I switched carb positions, tried used coils, different plug wires and anything else I could think of. Same cylinder refused to run. Nothing worked. Finally reduced plug gap from .025" to .022". And voila, it ran. Go figure. It has since always been sensitive to plug gap.

More leg?

I doubt you sheared a key on a timing gear. You'd know something was really wrong if that happened.

For peace of mind, pull both plugs, turn the motor over with the kick start by hand if possible, and look in the plug holes to check if the valves are opening and closing. Probably are. While you are at it, adjust the valve lash.

I can't imagine not being able to get fuel in the cylinders with those ticklers. From distant and poor memory, the bike should start even with warped intake flanges that aren't sealing well. It won't idle long sucking air in past the o-ring intake gaskets though.

When I installed an epoxy filled dual coil, I noticed that the spark, although present, was nowhere near as bright. Hopefully you are not running battery-less, because that will wear your leg out trying to start the motor.

With Mikuni carburetors, contrary to the normal procedure, I had to open the throttle all the way and kick the motor over 3 times ignition Off to get some fuel in the cylinders before I could turn the ignition On and try to start the motor. I can't remember what I did with the Amals, but I think the bike was a lot easier to start with Amals. points, and oil filled coils.

Anyway, I felt your pain. I fixed my startup issues, but not with Amals. Good luck

Great replies. Dark now and dinner time. But first thing tomorrow I shall crack on with your suggested tips.
Hope to post positive results.
Thanks guys.

My Triumph T-120 had always been an easy starter cold or hot- 1-2 kicks. I put it up for the winter 2 months ago with a splash of Seafoam. Lately it has taken 20 kicks to start. Probed out the idle air jet, cleaned plugs, checked timing with strobe. Still not starting. Put in fresh gas and.............bingo- starts easy. I guess the sitting evaporated the lighter gas components or Seafoam was causing this. You might try fresh gas
Doug

bluuman said:

I am trying to resolve a starting issue with my 1971 750 Commando. Just fitted Pazon ignition and Pazon HT dual coil.
Static timed it as per instructions. Good sparks on kickstarting with plugs out.
But no matter how many times I kickstart it, even with say half throttle, the spark plugs are bone dry and no smell of petrol.
I have twin concentrics and both bowls flood on ticklers ok. I have had these carbs apart and blown through all the jets.
Inlet valves close properly and engine compression is good on both barrels.
Surely the plugs will become slightly wet?
Any clues?

Click to expand...

If you have the standard rotor with two timing marks, you may have used the wrong one and be 180 degrees out - it will spark fine, just not when it should. IMHO, the throttle should not be touched while kickstarting a tickled bike - you want it rich and opening the throttle makes it lean when starting.

marshg246 said:

If you have the standard rotor with two timing marks, you may have used the wrong one and be 180 degrees out

Click to expand...

With the plugs out, ignition off, put a finger over one of the plug holes. When you feel compression developing align the first available timing mark; at this point the trigger magnets on the ignition rotor should be aligned or very near the coils they induce the ignition signal, if they are about 90 degrees off then reset as marshg246 pointed out.

Best.

" even with say half throttle"
There is the problem. No vacuum, no fuel. Any carb, any vehicle.

Make sure your using the counterclockwise timing hole and not the clockwise rotation hole

"I have had these carbs apart and blown through all the jets."

Unless you have VISUALLY VERIFIED flow through all the carburetor PASSAGES, you cannot be sure of them. The tiny drillings into the bore. Use aerosol brake clean to test.
(disclaimer for fumb ducks, "be careful to not get it in your eyes!")

A teaspoon of gas in each sparkplug hole, as a quick test.
I've written it before, "make the plugs wet".
O.P. knows this.
Guessing at ignition possibilities without confirming fuel flow (via wet plugs) is hardest way to solve the no-start problem.

concours said:

"I have had these carbs apart and blown through all the jets."

Unless you have VISUALLY VERIFIED flow through all the carburetor PASSAGES, you cannot be sure of them. The tiny drillings into the bore. Use aerosol brake clean to test.
(disclaimer for fumb ducks, "be careful to not get it in your eyes!")

Click to expand...

True and the pilot jet has to be poked or drilled through if blocked. Blowing or squirting aerosol stuff doesn’t usually work.