spark plugs dying young

The bike starts and runs fine- when I can find good fuel!
My spark plugs seem to last only 1,000 miles or less, especially when I rev it up a few tines during a ride. It drops a plug during the cruise home. This has happened to me twice now, so I just change out the set of them. If I keep it below about 6 grand it works just great, but if I crank on it a couple times during a ride it won't drop a plug immediately, but usually during the cruise home. It doesn't make any sense to me and I'm getting quite a collection of bp7es plugs in my toolbox... any ideas? 8)

 

What do you mean the plug drops? Is it getting fouled? If it is, trace the source of your fouling...i.e. it isn't actually running fine, just running.

Or is it the same plug that stops working? Did you switch it out with another cylinder? How can you tell that a plug fails while riding?

Are these the recommended plug for your bike (what bike/put it in your sig)?

 

Float levels too high and you're saturating them?

Loose resistor core in a plug cap so they're getting "cooked?"

Plug cap loose on a wire, causing the same issue?

 

Too lean hammering the plug to death?

 

the plugs look fine when I remove them- nice light brown electrode- dry. One just quits firing and I limp home on 3 cylinders. I install a new set and away we go- runs perfectly. It's a strange one! No problems at all other than this- everything works perfectly. This is a headscratcher for me too...
proper plugs
caps and wires look new
unknown which cylinder, the plugs all look identical when removed, light brown, dry electrode.
Idea: I'm gonna test them all on my dirt bike for fire... if they all fire then I have a coil breaking down. sound like an idea?

 

Get rid of those NGK plugs and plug in the Autolite equivalents. See what happens. BTW, I'm assuming that it isn't the same cylinder failing every time, if it is you should know that this is an obvious red flag to another problem.

 

I have never heard this before...

 

I haven't isolated which cylinder, but the plugs all look fine and the thing runs like a rocket- a friend's Vulcan Drifter 1300 can just barely pull me in a drag race!
We used to have the occasional plug crap out on 2 stroke dirtbikes so perhaps changing brands is worth trying. Thanks for all the advice!
8)

 

If you see evidence of the Plug being fouled or having run lean; I'd suspect the Plug Wires (and other Ignition-related issues) right off the bat.

An "Ignition System" upgrade is something we are all facing if we plan on running these bikes beyond 30 years or more.

Fuse Panel is overdue.

Performance Coils and Wires are rapidly moving up the list as needed replacements for reliability.

If you have an Inline Filter ... Immediately suspect that.
Remove the Filter and "Blow" through it.
IF, the Filter resists being PURGED, ... get rid of it.

Replace it with a larger Fuel Filter that you conceal behind the Side Panel.
Keep the Filter lower than the Tank and Higher than the Carbs.

 

fuse panel is clean and functional.
coils and wires look nearly new.
At this point I don't have an inline fuel filter on it- but you gave me good ideas about mounting one.
Leanness: was my thought since I am at 4000 feet and ride higher than that.
the body end of the plug is black, but the electrode is clean, the ceramic is chocolate brown and dry. hmmm.
As soon as I check all those spark plugs I'll post the results.
THANKS for all the ideas! 8)

Is there an easy way to adjust mixture or are we talking individual rejetting?

 

If a coil was bad you would have 2 cylinders that don't fire, so since you have only one plug go bad check your plug wires. Hook your meter( set it for continuity) to the mount for ground and put the other probe in the plug wire end and move the wire around while making sure you are maintaining contact, and watch your meter needle. If you have good continuity, then your coils are OK.

 

"I have never heard this before..."

You have now.

 

Steve, think about this a minute "If you have good continuity, then your coils are OK."

 

Continuity?

There's continuity between the Motor Mounts Bolts.

You can try an Old Shade-tree trick that the Hot-Rod Boys uses to do when they tested for a miss.

Solder a 4-Foot length of Ignition Wire to the Shank of a Long, Plastic Handled Screwdriver.
Attach a Alligator Clip to the Bitter-end.

Ground the Screwdriver to the Block.
Run the Engine.
Rub the length of each Spark Plug Wire.
Listen for a Misfire.
If you hear a change in rpm's, ...

Look to see if the Wire will Arc to the Screwdriver.

You can put "New" Wires on the Coils for short money.
Go to a Junk Yard.
Grab some long Plug Wires out of a Benz, Audi, Beemer or VW.

Do the YAMAHA "Coil Surgery" and replace the Stock Wires with some Stainless Core Performance Wires from Bosch

 

Why pull used plug wires out of a nice car? Couldn't those wires be bad too?

 

The Plug Wires out of a late-model wreck are usually very nice stuff.

If you grab wires out of a 5-Series Beemer, ... they're top shelf. $75-125.00
a set.

Stainless steel Mag winding, 100% pure silicone jacket, Kevlar reinforced core
EPDM (synthetic rubber) inner insulation.

 

You keep saying "look" in regard to the wires and plug caps. Looking isn't all there is to it.

Inside the caps is a resistor "core" that screws into the cap, and the spark plug tip actually plugs into that. It is not uncommon for these to come loose. CHECK THEM. Pull the cap off the plug, and look in the hole. You'll see a set of screwdriver slots on either side of where the tip of the plug goes. Using those slots, gently ensure the cores are not loose.

The caps themselves screw into/onto the wires. Remove each cap by unscrewing it from the wire, cleanly lop off about 1/4" ~ 3/8" of the wire, and screw the caps back on. There is a threaded spike inside the cap that screws into the center of the wire. This will give the caps a new "bite" on the wires; be careful not to overtighten when screwing them back on.

 

Am I correct is assuming our fact list to diagnose from is;

Engine missfire soon after a high load run, on a unknown cylinder.
Solved by replacing the almost new plugs, until the next high load run.
Plugs just removed look good.

More info would be nice.
Can you spray some water on each exhaust pipe near the head to see if it evaporates off equally when its missing? This can help trace a missfire.

 

if your wires are good, you should be able to grab them with a wet hand. let us know what happened

 

That's not nice...

 

Yes, but not 30 years old or exposed to elements like bike wires were/are.

 

Yamaha plug wires are molded into the coils; replacing them isn't an easy task so it shouldn't be undertaken unless necessary.

There are a lot of diagnostic steps to be taken first.

 

If it only occurs at high-rpm's ... there is a chance that you have a Carb with a partially clogged Beenie-Screen.

The Float Height would Test OK, ...
But, the "Fill-rate" would be slower.

Such that at High Speed you'd Fuel- starve the Hole with the Supply problem causing it to Miss.

Sometimes people neglect to pull the Float Valve Seats during cleaning.

 

Did you check for sparks in all spark plugs? If you run in 3 cilinders is because one is not firing most likely because it's has no sparks. If you don't have spark in a cilinder try the other cilinder that is fed by the same ignition coil for spark, is not usual but it happens to me that I had spark in #4 but not in #1, replaced the coil and the problem's gone.