2004 dyna fouling rear plug

[Moparnut72]

Have you verified the compression readings? What you had is pretty low. You need to figure this out before you start throwing parts at it. If these figures are correct you will need to figure why. A leak down test would be high on the list.
kk

[PoorUB]

Does the one spark plug look wet and oily? Maybe the intake valve stem seal sh*t the bed and died big time and you are sucking in oil and fouling the plug. Rich would be dry, black and sooty. Oil would be wet, black and sooty.

Know anyone with a bore scope? A little mini inspection camera? Hold open the throttle and take a look down the intake of each cylinder and check over the valves and guides. If they are wet, you have a valve stem seal are guide leaking oil.

[rigidthumper]

Just pulled the injectors and the rear looks kinda burnt. I swapped em front and back and will fire up in morning to see if the front starts fouling the plug. If so i guess i need a new injector. Then i can run her over to the dealer and run another compression test.

Put 2 new fuel injectors in, got her all buttoned back up and still sounds like "Potty mouth" and rear cylinder fouling out. Now it looks like front is too lean as well. Have no idea what to do from here. Man spent the whole day working on it and still back to square 1.

Thought you were going to swap injectors? Assuming the new ones are OK, that leaves intake seal issues, wiring, or coil. I'd put the original injectors back, swapped, and check injector wires, replace the intake seals just because they're old, and try again- if same same results, swap coil with known good unit. 

[anthonyflhx]

Had issues with swapping injectors and they looked pretty bad shape. The rear looked almost broken with burned edges. Figures I'd just bite the bullet and put new ones in so i didn't have to go through that twice.
Swapped coil for working one and same issue. New plugs, new wires and flushed tank and new hi octane gas with injector cleaner. New intake seals and sprayed wd40 around intake to make sure there's no leaks. Im stuck and baffled.
Still same issue.

[rigidthumper]

So, no one has changed anything in the tune, right? No fuel pressure issues, no power commander etc? Sounds like we're down to a wiring issue or mechanical issue.  Time to pull on the injector wires, to check for a conductor broken inside the sheathing, or bad pins.  Front injector harness should have white/yellow wire, rear injector should have green/grey wire.  Good thing it's winter...

[anthonyflhx]

I tried pushing on injector wires when bike was idling and didn't hear any change in idle. I'll give it another try.
The tune was a sert tune i think from previous owner.
I was worried it might be a valve issue but tech at Harley said i would know it if it was a valve issue as it would be loud and noticeable.

[FXDBI]

I tried pushing on injector wires when bike was idling and didn't hear any change in idle. I'll give it another try.
The tune was a sert tune i think from previous owner.
I was worried it might be a valve issue but tech at Harley said i would know it if it was a valve issue as it would be loud and noticeable.

Valve seals on the rear head leaking and fouling the plug.  Bob

[Hossamania]

I tried pushing on injector wires when bike was idling and didn't hear any change in idle. I'll give it another try.
The tune was a sert tune i think from previous owner.
I was worried it might be a valve issue but tech at Harley said i would know it if it was a valve issue as it would be loud and noticeable.

Valve seals on the rear head leaking and fouling the plug.  Bob

They would not be loud and noticeable.

[anthonyflhx]

I was afraid of that. How can i confirm its the valves?
So i have to pull the heads and have the valves redone? Might as well do both while I'm at it. How much does something like that cost?

[FXDBI]

I tried pushing on injector wires when bike was idling and didn't hear any change in idle. I'll give it another try.
The tune was a sert tune i think from previous owner.
I was worried it might be a valve issue but tech at Harley said i would know it if it was a valve issue as it would be loud and noticeable.

Valve seals on the rear head leaking and fouling the plug.  Bob

They would not be loud and noticeable.

If you keep running it with them leaking and get it hot it will grab a guide and get very loud and noticeable. Don't ask how I know.   Bob

[FXDBI]

I was afraid of that. How can i confirm its the valves?
So i have to pull the heads and have the valves redone? Might as well do both while I'm at it. How much does something like that cost?

Pull the rear exhaust and look in the port, stock heads? How many km on them and the rest of the build?  Bob

[anthonyflhx]

Stock heads 59k miles

[jamminhd2000]

Have you verified the compression readings? What you had is pretty low. You need to figure this out before you start throwing parts at it. If these figures are correct you will need to figure why. A leak down test would be high on the list.
kk

[kd]

Passing a leak down test could also confirm the compression gauge to be reading low. Then it would be worthwhile to try a known good gauge for the retest.

[nosjunkie]

A leak down would be more accurate than a comp check.. also lets you know where the culprit is...

[PoorUB]

I was afraid of that. How can i confirm its the valves?
So i have to pull the heads and have the valves redone? Might as well do both while I'm at it. How much does something like that cost?

I mentioned a bore scope/inspection camera in a previous post. Short of that, pull the intake manifold and you can get a pretty good look into the intake ports. Any oil around the valve stem should be very noticeable.

I asked earlier, is the fouled spark plug wet or dry? Oil fouling will often leave an oily film. Too much gas looks dry. Other than that either condition will look about the same.

[fbn ent]

Probably premature but....Is it using any oil? If it is 59K on the original motor and you are stuck in Winter, I would pull the top end and get a freshen. I assume the cam chain tensioners have been addressed...

[1FSTRK]

Just did compression check and each cylinder was at about 125. Is that good or bad reading on a cold engine?

Before you go tearing apart the engine slow down a little. It does not matter if your gauge is off or your compression is low, both cylinders read the same pressure yet one plug is black and one is white.
This should tell us the compression is not the main cause. In both cases of plugs you posted the one plug looks to be dry and powder black not real shiny and wet, this should mean fuel.

One of the most experienced guys here is giving you some of the best advice, slow down and follow it step by step. You may end up in the engine but at least you will not start by needlessly rebuilding only to have to go back and find the actual problem once the new engine is running. I would start with his first post here and follow this guy.

So, no one has changed anything in the tune, right? No fuel pressure issues, no power commander etc? Sounds like we're down to a wiring issue or mechanical issue.  Time to pull on the injector wires, to check for a conductor broken inside the sheathing, or bad pins.  Front injector harness should have white/yellow wire, rear injector should have green/grey wire.  Good thing it's winter...

[Norton Commando]

Before you go tearing apart the engine slow down a little. It does not matter if your gauge is off or your compression is low, both cylinders read the same pressure yet one plug is black and one is white.

This should tell us the compression is not the main cause. In both cases of plugs you posted the one plug looks to be dry and powder black not real shiny and wet, this should mean fuel.

Indeed I was thinking the same: the plug looks fluffy black and I didn't see oily threads on the base of the plug.

So at this point it appears that the problem is too much fuel or insufficient ignition on the rear cylinder.   

Best,

Jason

[Armin]

Just did compression check and each cylinder was at about 125. Is that good or bad reading on a cold engine?

This should tell us the compression is not the main cause. In both cases of plugs you posted the one plug looks to be dry and powder black not real shiny and wet, this should mean fuel.

So, no one has changed anything in the tune, right? No fuel pressure issues, no power commander etc? Sounds like we're down to a wiring issue or mechanical issue.  Time to pull on the injector wires, to check for a conductor broken inside the sheathing, or bad pins.  Front injector harness should have white/yellow wire, rear injector should have green/grey wire.  Good thing it's winter...

If your cylinders, pistons and heads are left in stock condition your ccp at WOT should be between 155 and 165 depending on rings and cylinder wall conditions with component variances considered and I believe that 125 psi ccp is too low but, as quoted above, should not cause this uneven burning situation.


The injector receives the open command from the ECM by pulling the gn/gy wire to ground. One way to possibly find the culprit is to detach the large connector from the ECM and measure the resistance of pin 19 of the connector to ground using an ohmmeter. If it reads zero or anything close to zero steadily or temporarily then wiggle the harness holding the gn/gy wire to hopefully find a broken insulation causing the excessive injection to the rear cylinder.

Armin.

[anthonyflhx]

Ok wiring is definitely not my forte, but i gave it a shot. I used a woods analog multimeter and it has an ohm setting. The 2 omega options are 10x and 1000x. I set to 1000x and connected the red lead to pin 19 and the black to ground using frame. The needle moved to 1 ohm and stayed steady. This is with bike off and the 2 fuel injector plugs disconnected.
Am i following correctly so far? To get to the 2 plugs i had to remove the tank. So what is next step? Do i start opening threw protective tubing holding all the wires together? Should i turn ignition on to see that the ohm meter does?
Appreciate your patience and help. This is all new territory for me. Many thanks in advance.

"The injector receives the open command from the ECM by pulling the gn/gy wire to ground. One way to possibly find the culprit is to detach the large connector from the ECM and measure the resistance of pin 19 of the connector to ground using an ohmmeter. If it reads zero or anything close to zero steadily or temporarily then wiggle the harness holding the gn/gy wire to hopefully find a broken insulation causing the excessive injection to the rear cylinder.

Armin."

[kd]

Do NOT use an ohmmeter on a live circuit. It'll damage your meter.

[jls 64]

1.leak down test.
2.pull intake and take a lock
3 pull ehaust take a lock exhaust port.
4.rear inyector
wiring harness.
5.pin17 on main wire harness.

[barny7655]

gee this post has drifted away from what the first post is seems no firing rear cyl carbon on plug,causes ,1/ wiring loom, test with injector with pulse tester , 2/ change  spark plug 3/ comp test 4/ vacumme leak  test  ,5/ ignition module test , test with another if possible ,6/ fuel line to injector ,as jls has also put some ideas forward, it should still fire with new plug if oil is leaking into cyl from inlet ,try this all out ,wouldnt even look at any thing major as yet, it will be a simple thing KISS, cheers

[Hybredhog]

    '04 were not a closed loop system, maybe it is just an intake leak?