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.

[MikeL]

If no mechanical defects are discovered like a bad valve guide, broken ring scored cylinder etc. Trying out a different ignition module would be worth a try. Usually an exhaust backfire is caused by something in the ignition system. Could be a coil or the rear plug wire. Havn't seen a bad wire or a coil on a T/C yet but "Potty mouth" happens........


                                                                                                        MIKE

[starrider]

Tyner...when tinkering with the old 60s cars...i would go one heat range higher on the plug and advance the timing 5 degrees... Is it a common practice to go a heat range higher or two  on a twin cam?

Mikel...I don't think anything is broken...rings ...valve guides... when i put in a set of new plugs the engine runs great ...for a while...thinking the backfire was probably a fluke of over rich AFR at the time...probably something simple as new wires are needed...as mention by others.

The bike is still an 88 incher...don't need any more cubes...of a faster or more bigger powerful engine...and happy with the 5 speed trans. Have ridden this bike since new...a daily or rather a nightly rider hence starrider.

Thanks for your thoughts!

[Roadflyer]

If you never have to use the choke, your bike is running too rich.

[smoserx1]

 
Missed that one!

[kd]

If you never have to use the choke, your bike is running too rich.

    Took the words right out of my mouth

[starrider]

Ok...Guys this is how i cold start my RK...

(1) first to avoid kick back ( where you try to start the bike and it fails is a crashing terrible sound in the engine)...(have heard others bikes do this when rider attempt start )...ok to avoid this...with the throttle closed... i tap the starter twice with the intent to release any gas pressure build up that may cause this crashing engine failure sound...

(2) Then i twist the throttle 5 times...while NOT hitting the start button.

(3)Then i hit the starter button to start... as the engine fires up i will open the throttle  gently and steady while the engine is firing up...

(4) After the engine is running i hold the throttle open at a low rpm idle long enough so it doesn't die until engine is warm enough to take off.

(5) Now re-starting a HOT  engine is a different procedure... with HOT ENGINE i keep the throttle closed...  and with one quick tap of the starter and engine fires up immediately...if i do it anyway different it will flood and i will get a kickback failure.

Every bike has it own personality?...this has works for me...a harley tech told be about tapping the starter a couple of times to act as a pressure release (on cold start) when  told him i was having a lot of kick back starts...which cost me a new ring gear and clutch basket job. Since doing this no more kick backs...

I DO NOT RECOMMEND THIS FOR ANYONE...this is just how i have started MY bike over the past years...(disclosure)

[Hossamania]

By pumping the throttle five times, you are effectively flooding the engine, doing  your plugs no favor.
How old is your battery? A marginal battery can cause kick back, I chased that problem for a while.
Might I suggest a different starting procedure?
Charge the battery to full. Bump your starter (optional). Set the choke, make sure it stays out. No throttle, hit the starter. If it doesn't immediately fire, twist the throttle slightly, release, start again.
The key to choke starts is to not touch the throttle.
Also, do a compression test at some point if you have not already.

[starrider]

Good Morning Guys...

Ok Hoss...good to know... Thanks!...The battery is two years old...always on tender
when bike parked. When i bought the bike new... i was taught by the dealer 'not to
use choke...as they said it flooded the engine' ...so that's why i never used the choke.
In fact ...that was what the advice from them in 2000 with my first bike ...a Heritage.
'Just give the wick a couple of twists and hit the starter' was the service policy.
Like i said... i always learn from this forum...now the electrical may be a contributor...perhaps not enough juice ...battery ...coil...wires...?
....or just not running the bike long enough. Like i said...i am a everyday rather night rider. I just fire up the bike and take her for a spin for 30 minutes through town... some stretches reaching 50 mph or more. This is at night...a lot of times as late or later than midnite. So the point is perhaps the engine being ran for only 30 minutes isn't getting hot enough?...i do like to ride when the weather temp is 65-70 degrees.

Thanks!...

[SixShooter14]

Good Morning Guys...

Ok Hoss...good to know... Thanks!...The battery is two years old...always on tender
when bike parked. When i bought the bike new... i was taught by the dealer 'not to
use choke...as they said it flooded the engine' ...so that's why i never used the choke.
In fact ...that was what the advice from them in 2000 with my first bike ...a Heritage.
'Just give the wick a couple of twists and hit the starter' was the service policy.
Like i said... i always learn from this forum...now the electrical may be a contributor...perhaps not enough juice ...battery ...coil...wires...?
....or just not running the bike long enough. Like i said...i am a everyday rather night rider. I just fire up the bike and take her for a spin for 30 minutes through town... some stretches reaching 50 mph or more. This is at night...a lot of times as late or later than midnite. So the point is perhaps the engine being ran for only 30 minutes isn't getting hot enough?...i do like to ride when the weather temp is 65-70 degrees.

Thanks!...

are you giving it a bit of time to warm up?

I usually let mine idle until I can feel some heat through the rockerbox. Then I start out easy for a few bits as I get out of my apartment complex. This lets the case, cylinders, heads, and rockers get warm and expanded. Most days when it's in the 60s or more it only takes maybe 45secs or less of idling to feel the heat start creeping up from the head. Colder days take a minute or 2.

[starrider]

Good Morning SixShooter14

When i first start up... i try
to...for about 3-4 minutes...then idle off slowly as i make my way to the main drag. The reason ... don't want to piss off the neighbors...as it is late 12 midnite sometimes 130 am...and those Vance and Hines mufflers are not the
quietist ones...hence 2-3 minutes unless the weather temperature is in the 40s then
longer warm up time ...say 5 minutes... By the time i make it to the main drag...wait at a stop lite...the engine should be warmed enough.

Thanks...!      

[Hossamania]

Your bike is getting plenty warm and plenty of time to recharge the battery in a 30 minute ride. Your rides are actually pretty ideal in that regard. Keep using the tender as well.
I don't know why people are told not to use the choke. It is the proper method for starting. It will not flood the motor when used properly. I believe it is much easier on the motor than having to keep working the throttle to keep it running. It will also slide in on its own normally, though they do stick sometimes, and need to be pushed in when warm, or sometimes they don't stay out and need to be held, an adjustment nut solves that.
I have always used the choke to start my bikes for well over 25 years and 160,000 miles or more. I have never done a quick starter bump before just pulling the choke and starting. I just pull it and hit the starter. I may give a small a small throttle twist if it has been a while (a week or more) or is rather cold out. Do not use the throttle with a choke start, the throttle should stay closed.

[starrider]

OK Hoss...Thanks again! we will use the choke...