Spark plug

[starrider]

Hi Guys...

On my carb 03 RK... the rear plug always starts fouling first after 50-100 miles or more?...
So when the engine starts running a little rough...i don't bother to check the front...and just change the back plug.

The engine has only 40k miles...has had the hydraulic cam tensioner fix with a
203 SE cam upgrade.

Have been using HD's high performance 'Screaming Eagle' spark plugs.

Thanks in advance...

[smoserx1]

Shouldn't be doing that at all.  Could be time for a new set of wires.  If that does not work you may need a coil.

[bobrk1]

Also  make  sure  that  the  choke  cable  is working  right  and  going  all the  way  in.

[Hossamania]

Along with plug wires, you may want to do a leak down test on the motor to eliminate a leaking valve or worn piston rings.
How do you normally ride, higher rpm's at cruise, higher rpm's when shifting, or low rpm cruising, short shifting to avoid rpm's?

[chaos901]

Agree with the leak down test needing to be done. 

Is it fouling from oil?

[rigidthumper]

Replace intake seals while you're there.

[speedzter]

Is this a new issue, or been there for ever ?
Has the bike ever had the AFR's checked ?

[starrider]

Thanks Guys ! ...all good suggestions to follow up on...new wires...if i got new wires...would 8 mm make a hotter or better spark than the stock 6 mm wire?

Check the choke?...never use the choke... good idea ...never know it could be pulled out a bit.

Air fuel mixture...yes... i guess that could be a factor...it's just that if it was too rich...
would not both plugs go dark at the same time?

Now staying on AFR... i have  neglected the air filter...which could create an overly rich AFR... I did pick up a new K&N filter.

Hoss ... i don't have a tach on the bike...just go by feel...when the gear has reached it effective pulling ...i blip the throttle to keep the rpms up to meet the trans when going to  the next gear up or down...as far as cruising on the city streets i like to keep it in the rpm range to where i can feel the tork on the wheels so ... if i need  that throttle power...we'll have it.

Thanks Guys...always have learned a lot on this forum...

[sandrooney]

Is it oil or gas fouled?

[smoserx1]

Thanks Guys ! ...all good suggestions to follow up on...new wires...if i got new wires...would 8 mm make a hotter or better spark than the stock 6 mm wire?

IMO no, but it shouldn't hurt anything either.  I have run them.  They don't fit into those little routing clips under the tank very well cause they are so fat.  Try switching the ones you have (must do at both the plug and coil ends) and see if the issue transfers to the other cylinder.  If so you found your problem.  Also remember that coils rarely fail but I have heard if they do it is usually when  they get hot.  A problem with just one cylinder to me is not indicative of a dirty air filter ot improperly jetted carburetor.  Seems those issues would affect both.  Excessive oil consumption or poor compression/leakage in just one cylinder may very well be though.

[speedzter]

You didn't say how long it's been happening or when it started ?
A carb'ed bike will nearly always run one cylinder richer than the other.

[MikeL]

You didn't say how long it's been happening or when it started ?
A carb'ed bike will nearly always run one cylinder richer than the other.

I agree, on all my carb bikes the back cylinder is always darker. In the case where talking about here if the back plug fouls to miss fire then the front plug isn't that far behind. We do not know what carb is used here. If it's a cv then it could have been "re jetted" to compensate for the mild 203 cams a little too aggressively. Same goes for an S&S or Mikuni
Switching wires is difficult due to the lengths the twin cams are single fire.
We also don't know if this problem started after cam/ plate upgrade. If it did maybe there is a miss alignment of timing marks.........

                                                                                                       MIKE

[starrider]

Good morning Guys!...on my second cup of coffee now...Ok it's a cv stock carb. When did i notice the spark plugs?... guess it would be a year after the cam  and cam tensioner kit upgrade... before upgrade... the cv was jetted for stage one and running V&H mufflers. The bike ran good without a hiccup for a year since the upgrades.

Rear cylinder on carb bikes run darker?...Ok kinda thought that might be the case here...thanks good to know!...

Ok...so last night went for my usual late night ride...put in fresh set of plugs and alway runs perfect for a while...although on the way back ... it did have a few hiccups and then the first loud BACK FIRE on the pipes...Wow!

[doctorevil]

did you check the float level and needle ?

[smoserx1]

So you are saying you went out for a ride last night with a set of NEW plugs and the back one fouled?  I am not buying this argument about the rear plug running richer than the front being the problem.  If it happens it is very subtle.  I have a bike with a stock CV carb and yes I can tell a little color difference front to back but not much at all.  Also whenever I have changed plugs it takes several rides or days before any real color change takes place.  Until then everything is snow white.  Anyway it would be nice to see a clear pic of both plugs after this happens.  If your carburetor was adjusted  badly enough so the rear plug fouls after one ride and the front were close behind I would think your bike would be getting very bad gas mileage, be way down on power and gagging you (or anybody behind you) from gas fumes, and both plugs black as the ace of spades.  I would still try switching wires.  Someone said it was difficult (due to being single fire???)  I don't understand, it should similar to my FLHT and I don't consider that to be too bad at all.  You obviously have a problem and need to work to get to the bottom of it.  Good luck

[starrider]

No ...not at all...as you said it takes several rides or more...before i notice the engine starts to run a little rough ... and that is the time when i change the rear plug and it is quite darker than front. I never wait til the plug actually fouls... when engine sounds rough... i change it and notice that it is quite a bit darker... would like to take a pic... when i figure how to i will...
All i can say is comparing the two plugs when changing both out one time...the porcelain white
and electrodes light gray on front...the back one was very dark...so that is when i just started changing the rear plug and not bothering with checking the front. As far as the fresh plugs i just put in...assume they are still good...haven't checked them yet.

Thanks for your advice smoserx1 ...

[chaos901]

So, is it fouling with GAS and not OIL?

[starrider]

Ok...how can you tell by the plug if it is gas or oil...? I here to learn... The plug porcelain everything is dark... You guys are my teachers...

[rigidthumper]

Shiny black is typically oil, fuzzy black is typically fuel

[starrider]

Thanks rigidthumper...looks like a dry not shiny dark...so gas?...

[rigidthumper]

Sounds like fuel. You may want to pull the air filter off and look at the stream of fuel coming out of the accelerator nozzle when throttle is twisted. Sometimes it's aimed crooked, so the entire stream goes intro the rear cylinder.  If you're careful, you can direct that stream so it hits the main jet and breaks up before going into the manifold.  I have a skinny pair of needle nose vice grips I use for that- careful, the nozzle can be crushed.

[starrider]

Thanks rigidthumper... and Everyone !...

[SixShooter14]

Sounds like fuel. You may want to pull the air filter off and look at the stream of fuel coming out of the accelerator nozzle when throttle is twisted. Sometimes it's aimed crooked, so the entire stream goes intro the rear cylinder.  If you're careful, you can direct that stream so it hits the main jet and breaks up before going into the manifold.  I have a skinny pair of needle nose vice grips I use for that- careful, the nozzle can be crushed.

I don't think I'd ever check that. Good idea. 

[boooby1744]

And once that is figured out,maybe a DTT ignition (set to multi spark) and a pair of Denso iridium plugs.

[Tynker]

Thanks rigidthumper...looks like a dry not shiny dark...so gas?...

I would try running a rear plug with 2 heat ranges hotter, and see what happens.