spark plug heat range question

[ΚĜΗΟŜΤ]

My build,

2004 softail standard. 95 inch, S&S 570 gear drive, SE forged pistons, Daytona twin tech ign. Street port level head work and intake manifold. CV-40 ....~ 10.25:1 compression.

removed heads last night to have compression release holes machined into heads.
Noticed that the rear is running much richer than the front, Spark plugs were very carboned up and the piston had a fair amount mainly in the center, the outer edge ~1/2 or so of the piston was fairly clean.
Front head and spark plug looked normal.
Spark plugs are NGK DCPR7E

Question is would running a hotter spark plug help to reduce the carbon build up on the rear?
thinking of going to a NGK DCPR8E for the rear cylinder.


Any thoughts??

[JimB]

If memory serves me... the DCPR7 is one range hotter than the DCPR8 - NGK goes up numerically (7 to 8 ) to get colder where Autolite & Champ goes down to get colder
In most rear cylinders Ive seen, they tend to run leaner/hotter than the front cylinder
Carbon is a result of unburned fuel & oil - Id suggest a retune of your EFI vs a plug change

My .02 worth at 6am in the morning

[ΚĜΗΟŜΤ]

This is a carbed (cv-40) motor.

I have been told carbed the rear cylinder runs richer

[JimB]

Ooops... I saw Twin Tech & my brain thought EFI....my bad

[Admiral Akbar]

Change the valve seals while the heads are off.. Look at the build up on the back side of the intakes.

[ΚĜΗΟŜΤ]

Max I will do that.

Just a bit of background.
When the motor was built in 2011, the following summer ~ 3000 - 4000 miles of use, I went to check the spark plugs and there seemed to be a an excess a carbon build up on the rear spark plug. I took it back to the builder and he looked in the combustion chamber with a bore scope but nothing else and attributed the carbon to the rear cylinder running richer than the front.

I would say what the rear spark plug looks like is excessive to me with about 7000 miles on it......

Front head and spark plug

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[attach=1]

[ΚĜΗΟŜΤ]

Rear head and spark plug

Here are the pics

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[ΚĜΗΟŜΤ]

rear spark plug


[attach=1]

[a_disalvo]

Definitely agree with Max, oil seals will cause this.

[Admiral Akbar]

Need pics of the backside of the intake valves.


Add That's not AFR.. That's oil..

[ΚĜΗΟŜΤ]

I don't have a spring compressor so I will have to wait until I bring them to the head guy who is modifying them for comp releases.........to get pics of the back side of the valves....... I have a new set of seals if needed!!

[Admiral Akbar]

I don't have a spring compressor so I will have to wait until I bring them to the head guy who is modifying them for comp releases.........to get pics of the back side of the valves....... I have a new set of seals if needed!!

There should be a hole in the side of the head where you can see the back side of the valve..

[FLTRI]

[attach=1] [attach=0]

Rear head and spark plug

Here are the pics

Looks like oil not fuel. As Max iluded...look at the back of the valves from the intake and exhaust ports.
Bob

[ΚĜΗΟŜΤ]

Update::

Took the heads to my friend who did the porting and talked me out of the compression releases to begin with, He has the gig for drilling them and did them for me for free, He delivered the heads to the shop that did my build back in '10/'11.

The lead builder completely went thru the heads, blasted them clean, cleaned all the valves, lapped all valves, BRAND NEW SEALS, discussed that this was an issue from the beginning and he agreed (bad/leaking seal (s).............No charge!!

Got motor back together Monday evening and finished all the other stuff like carb, gas tank...etc..

Bike fired right up and with the comp releases it now starts like a dream!! No strain on the starter and basically starts effortlessly!!

Will get some miles on it over the next week or so and check the plugs for any signs of anything  and hope to see two equal colored plugs........fingers crossed!!

[Buffalo]

It has been my experience that the rear cylinder on my carbed 01 always showed slightly darker (richer) than the front.  I never had an oil seal issue, but always saw a minor difference. Since the rear cylinder does run a little hotter than front, slightly richer in the rear helps to moderate temps imo.
I would run the colder plug NGK8, or stick with stock HD plugs. I believe the difference in colors involves the way the manifold system works on a staggered twin.  fwiw Buffalo

[Admiral Akbar]

Update::

Took the heads to my friend who did the porting and talked me out of the compression releases to begin with, He has the gig for drilling them and did them for me for free, He delivered the heads to the shop that did my build back in '10/'11.

The lead builder completely went thru the heads, blasted them clean, cleaned all the valves, lapped all valves, BRAND NEW SEALS, discussed that this was an issue from the beginning and he agreed (bad/leaking seal (s).............No charge!!

Got motor back together Monday evening and finished all the other stuff like carb, gas tank...etc..

Bike fired right up and with the comp releases it now starts like a dream!! No strain on the starter and basically starts effortlessly!!

Will get some miles on it over the next week or so and check the plugs for any signs of anything  and hope to see two equal colored plugs........fingers crossed!!

[HogMike]

I don't have a spring compressor so I will have to wait until I bring them to the head guy who is modifying them for comp releases.........to get pics of the back side of the valves....... I have a new set of seals if needed!!

There should be a hole in the side of the head where you can see the back side of the valve..

Like this?

[Admiral Akbar]

I don't have a spring compressor so I will have to wait until I bring them to the head guy who is modifying them for comp releases.........to get pics of the back side of the valves....... I have a new set of seals if needed!!

There should be a hole in the side of the head where you can see the back side of the valve..

Like this?

[harley_cruiser]

What did he say caused the seals to go bad?
We're they hd or his brand?

[ΚĜΗΟŜΤ]

The guides used when the head guy did the heads were bronze, and are shaped.

He used Teflon (not sure what brand the seals are but he does many builds and has for many years) seals as these guides (according to him, the builder) are the only ones that fit. Viton seals, the ones I gave him nor the Viton's he had did not fit the guides.............so I have new Teflon seals. Not the best I know but it is what it is for now.

My ports, intake and exhaust look a lot different than the one pictured...(Massaged) but they did not look that clean when I removed the heads but they sure looked that way when I got them back. Both the intake and exhaust had a lot of oil on the back side of the valves (port side).

The engine builder is one of those few who can do all the motor machine and assembly work.......including antique stuff including making some parts from scratch........including piston for those old 1920's type of motor......

I have a fairly high degree of confidence in his work and judgment...Also when you put decisions in the hands of others they use what they know best....sometimes it goes without a hitch sometimes not so much........

[ΚĜΗΟŜΤ]

Follow up and end of my thread:

Back in '10-'11 I had my motorcycle motor rebuilt for more power...ya I took a perfectly good motor and had it rebuilt...... Anyway with the higher compression and higher lift cams I ended up with the typical Harley Kick back when starting it especially when hot. The fix for my situation was to have compression releases installed.
So two weeks ago I took my motor apart, A friend did the compression release machining and an Indy cleaned the heads up and installed new valve seals. Heads looked good as new. I reassembled the motor (in my driveway) Last Monday evening and finished installing all the rest of the stuff (gas tank, dash panel and carburetor) Tuesday evening.
Well a big thanks to Pete and Johnny as the bike starts effortlessly now and runs like it did when built...Sounds like a Hammer beating down on metal (in a good way) when I hammer it...lol

Also to note there was a bad intake seal and it has been present since the beginning soon after the build. Time will tell if it solves the issue.

Thanks
Jack