#1 cylinder is eating spark plugs

i actually never needed to open the engine yet. Everything imaginable on the bike was broken except for the engine itself.

These bikes have what is called a "wasted spark" that is when one cylinder has a power stroke(sparkplug firing) the other cylinder sparks on the exhaust stroke.

On my old 1982 GPz1100 B2, the left ignition coil fires #1 and #4 and the right ignition coil fires #2 and #3.

Which ever port is used makes not difference as they are wired the same, just make sure the primary(small wires) are connected correctly and the secondary(sparkplug leads) are going to the correct sparkplugs.

The ignition coils are nothing more than a step up transformer, designed to greatly raise the 12 volts from the battery to about 35K volts or so, by use of either points on the earlier bikes or the IC Igniter on the later ones by interrupting the ground circuit, inducing a high voltage in the secondary creating the spark in the plugs.

cobura wrote:

I just realized that on my z650b1, i have been riding on only 3 cylinders ever since i finished the rebuild. I replaced the spark plug (in #1 cylinder) and was amazed at the power increase, but the next day it fouled again. I am assuming that its because of a weak spark? The coils are original and probably not in the best of shape. Does this sounds right?

A coil always feeds two spark plugs in series. Since plugs 1 and 4 are in series and plugs 2 and 3 are in series, a problem with the plug/cap OR wire which causes either of the set to not spark (from an open circuit) also prevents the other plug from sparking. However, if one wire/cap is "arcing down" to ground the other plug can fire because it completes the circuit. Same thing if the coil is flaky and one end of the high voltage winding is arcing down to ground, the other end can still generate a spark.

cobura wrote:

If someone can help out, what aftermarket coils do you recommend? Should i go with the Dyno 3ohm coils?

I am running the four Ohm OEM coil that sells at Z1 Enterprises for $36 and it runs great in my 750 twin, a lot better than the stock coil.

Just interested in knowing what exactly was accomplished in this rebuild?

Reasoning, the coil, spark plug conductor/cap didn't go bad just sitting there. Assumption number 1 cylinder fired correctly pre-build correct?

Then what changed during/after the re-build.... Something not making sense here all...

I'm still with faulty (weak, not open)) plug conductor/cap or something else but a bad coil, naw not buying into that just yet...

Quick swap of 1/4 plug wires will tell quite a bit... should take about 5 seconds to accomplish... start her up, run for a minute or so, safely feel the temp on cylinder 1, still cold then coil not your problem.

Seriously, it's that easy.... before spending unnecessary $$$, trouble shoot and confirm for a set of plug wires is fairly inexpensive compared to a set of coils...

Same time, Dyna coils and ignition with new plug wires is always a cool way to go anyways.... So what the hell do I know.... :laugh:

get it running and spray dupli color paint in the air about ten feet from the carbs...works like magic.....omr showed me that one....

If not already done, would perform clear tube test on carb to non-combusting cylinder, thus determining whether fuel level is within specs.

A too high fuel level is likely to cause an excessively rich mixture, which quickly fouls the spark plug.

Good Fortune!

Thanks all for the help! Sorry I had to run out for a bit. In response to a question: I bought the bike as a project bike, so I dont know the history. What WAS done in the rebuild is a follows: New regulator and rectifier, new seat, new headlight and case, new turn signals, new chain, new tires, carburetor overhual, new spark plugs, new oil and oil filter, new air cleaner, new master cylinder, re-coated inside of gas tank, new speedo and tach cables, adjusted points, balanced the carburetor, and other stuff i dont remember.

After I finished the carburetor, the engine fired right up and it sounded fine. Ran fine too until the spark plug fouled. I'm a believer of "if it aint broke dont fix it." But if i do have reason to believe that its broke, then i wont hesitate to go ahead and open up the engine. Seems to be running strong though, I'd like to eliminate some other possibilities before i pull the whole engine out.

What "Patton" said is exactly what i'm thinking is the cause. I never replaced the float valves when i re-did the carburetor, it is probably running too rich in combination with the bad plug wires. I cant just change plug wires since the OEM type does not disconnect.

"I cant just change plug wires since the OEM type does not disconnect."...

Larry C and I just spoke on this for my 1000... Wanted it for testing and troubleshooting purposes for the time being.

They make a plug splice kit for these older coil/plug wire set ups... Z1 seems to have these, contact Jeff....

Same time, have the money then no doubt, upgrade the coils and plugs... Since you only adjusted points, get a new points and condenser kit as well for they're fairly inexpensive...

Let us know how it all works out...

You can't beat a new ignition.
But your likely too rich.

Have you done a proper vacuum sync yet?
I bet if you hvae the #1 carb is recieving a larger fuel charge for sure (throttle open more in that venturi) to compensate for richness.

Put a vac guage on there and play with the air mixture screw till you get the middle of the highest idle range for each cylinder, then re-do vac sync.

If you havnt vac synced your carbs, your just crap shooting!
Bench syncs are garbage!
GL!

"Bench syncs are garbage!"... How about a little additional info here... :laugh:

Tek is correct where Bench sync should not be used as your last adjustment no doubt but it is a good starting adjustment on a re-built set of carbs that where totally disassembled or where a PO or through 30 years of neglect are way out of whack for example...

Further tuning adjustments and syncing will be required once on the bike and in operation....

OMR

the carbs were vacuum synced already, but it might not be a bad idea to check them again. I just ordered 4 full carb rebuild kits from z1. I cleaned out my carbs real good before, but i didn't replace any of the hardware except for the jets. After I replace the float valves, maybe everything will be fine. As of now, i have a spark that should be enough if all else is working properly, which leads me to believe that its the carbs. One thing that i noticed when i first got the bike is that it still had the original spark plugs, or very old ones! I'm pretty sure i can say this because i could tell the plugs were ancient (old hitachi's that aren't even made any more). Im probably just trying to think positively, but I'd like to believe that the engine never had any problems with oil fouling plugs.