Troubleshooting a misfire problem...

Hi Guys- I'm having trouble with the Beast. The right cylinder seems to be misfiring- pops a little on idle, and then when accelerating it really lags, pops a lot, until I get up to pretty much wide open. Also there seems to be a lot of condensation on the outside of the carb, which is not happening to the left cylinder. It idles okay, but pops occasionally.
What I have already done is: new plugs, checked the plug wire contacts at the plug and coil, all coil wires okay and good connections. Fuel lines clean and clear, recently disassembled and cleaned carbs, mixture screw set pretty close to the other cylinder (about 1 and 1/4 turns out from closed). So I've exhausted my knowledge of carbs which isn't much to start with. Any and all help appreciated, thanks!

Did this problem start before or after you dismantled the carbs?
Maybe you have missed something in there.

Martyn.

Condensation on one and not the other would suggest uneven synchronization.

Yes ,pull off the aircleaner and get both fingers (from left hand) into both carb mouths and rest them against the slides. The right can slowly twist throttle. Should move at the same moment. That's the crude test. If you run the motor doing this your hand can be sucked into motor. Then how would you pull in a clutch ?

Okay, followed instructions and got both slides moving in unison, same amount of gap at idle, both start moving at the same time, move the same amount. Maybe a very slight improvement but still lots of misfiring and terrible acceleration. Wondering if it could be electrical? I've got the Boyer kit for points and a Sparx box. Thoughts? Thanks as always-

Hi
could be a build up of carbon on the exhaust valve stem stopping the valve from seating proper, a compression test will show it up, or take exhaust pipe off and have a look.
JohnT

Try taking off the coils and cleaning up the little screw-posts that often rust at the blade connectors. Then swap the coils when you put it back together as a test for both coils healthiness.

Take a hard look at ignition system.Try switching coils side to side.If misfire stays on right look at wires on pickup in points cavity they are known as a problem.I had similar trouble and replaced entire 15 year old Boyer with new MKIV and have had great performance since.
Craig

Update: removed coils, cleaned all contacts and connectors, all wires sound, swapped coils R to L, even checked plug wires and cleaned those contacts, swapped those R to L. Checked little wires in the Boyer. Everything checks out fine, misfire and popping continue. R&R sparkplugs, cleaned and gapped even tho they are brand new. Nada. I got nothin' left. Time to visit the shop and let Yoshi have at it. Very frustrating, especially since I just finished painting the tank and got it all lookin' good. Thanks for all the help and advice, I appreciate it- if you've got any more ideas, I'm listening, but I am out of my depth at this point. Aarrgghh!!!

Have you checked the carb manifold nuts are firm? Not unusual to have one come loose and that sucks air in the gap which, I guess sounds like the symptom the bike has.

The little wires in Boyer can fool you if just checked by eye sometimes cracked within insulation and very hard to find trouble visually.Also hope you tried all those checks one at a time. Your time is probably less expensive than Yoshi.Dig in !!!
Craig

Craig said:

The little wires in Boyer can fool you if just checked by eye sometimes cracked within insulation and very hard to find trouble visually.Also hope you tried all those checks one at a time. Your time is probably less expensive than Yoshi.Dig in !!!
Craig

Click to expand...

The little wires you speak of are changed from stranded to solid by the solder used on the pickup plate. Vibration will fracture a solid wire. Solder and vibration don't mix.

Update: tore apart the carbs again. found a clog in the jet that I had missed, or else it snuck in after I closed them up the first time- a little piece of gasket that must have nicked or torn off when I reassembled. Can't fire it up tonight but very hopeful about tomorrow!! Thanks for all the input- I will update again soon. Amazing how the tiniest simplest thing can cause such a colossal cluster. Thanks guys- eric

OK, Eric. We are all waiting for that update to see if it worked. I suspect many of us have had the same problem. Mine does not have the sweating carb, but I do get a sooty plug on the right that needs to be changed every thousand miles or so. Compression is a little lower on that side by about 20 lbs. too.

Hello All- Update at last. Ended up taking the "tear everything apart and fix everything so you never really know what the heck was wrong" approach. Strange symptoms often seem to be the result of multiple problems converging. So, I: a) fixed the broken wire to the coil, b) tore the carbs open again, polished the needles, polished the sleeves and slides, re-checked everything and reassembled, c) took apart the throttle cables and splitter and cleaned and re-lubed, adjusted the linkages, d) re-sealed the manifold-to-carb and manifold-to-head connections, e) checked and adjusted the slides to be in synch/moving together, f) started from scratch with the adjustments of mixture and idle stops per the Amal instructions, and g) had a beer. After all that, Mr. Norton started on the second kick. After quite a bit of fussing with mixture and idle, it roars like the lion it is. Still have a little trouble holding an idle, but that's why I always carry a screwdriver.

My best guess is the major culprit was the detritus in the jet and some apparent leakage of air at the manifold/head joint and manifold/carb joint. A little purple gasket sealer works wonders there. Thanks to all you guys for keeping me going and pointing me in the right direction! ejd