Did the brass rod mod...changed plugs and now i'm running lean

1885 Views 15 Replies 6 Participants Last post by stern-69, Jun 21, 2011

versicolor

Discussion Starter · Jun 8, 2011

Okay I replaced the aluminum rod and resistor in the plug caps with brass rod and installed the NGK DR8ES-L plugs. Took it out for about a 15 minute ride and checked the plugs when I got back. The condition indicated that it is suddenly very lean. Before doing this I had in the standard NGK D8EA plugs and the condition was perfect. The plugs were a nice tan/brown. So is this normal to see when doing this mod? I made no other changes. So i'm slowly adjusting the needles to try to get that brown/tan color back in the plugs. Just wondering if this is something that should be expected.

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Condo

· #2 · Jun 8, 2011

Blank

CXPHREAK

· #3 · Jun 8, 2011

You may simply be more efficiently burning fuel due to a better quality spark.

Shep

· #4 · Jun 8, 2011

I agree with Phreak.Just adjust your idle mixture to suit the new conditions.

Also see this thread about having doubled up resistance in the circuit,

http://cx500forum.com/index.php?/to...80334__hl__ignitech__fromsearch__1#entry80334

I run,"R" rated plugs but have UK none resistor caps,

http://www.wemoto.com/bikes/Honda/CX_500_A/79-80/

My fuel consumption is not as good as some posted on here but I have tuned Harley 883s exhausts and an Electric fan conversion.My lower mpg is almost certainly down to me and the throttle as my CX500s are supper nippy and I just cannot ride sedately for long<grin>

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versicolor

Discussion Starter · #5 · Jun 8, 2011

okay i'll keep adjusting. I think i'm getting to alot of turns out at this point. not sure how many because I set it to 3 when I first replaced the jets a couple months ago. But it's many more than that now. Maybe I need to go to a 130 jet instead of the 125 I have in there now?

CXPHREAK

· #6 · Jun 9, 2011

I tend to think that unless you are doing full throttle plug chops it will be the 78 jet that may need to go up a size or two.

versicolor

Discussion Starter · #7 · Jun 9, 2011

CXPHREAK said:
I tend to think that unless you are doing full throttle plug chops it will be the 78 jet that may need to go up a size or two.

So if i'm tending to have to turn the needles out too many turns then go up with the smaller jet? Right now I'm running 90/125. you think go up to maybe 95/125 and I should be able to have the needles at the more normal 3 or so turns out?

CXPHREAK

· #8 · Jun 9, 2011

I'm no carb expert so you would be best advised to wait for some of the more carb savvy on this forum to chime in before you go and order more jets or something but the smaller jet would be my gut feeling.

Looking at the mods to your bike in the photo you may be dialling it in for a while.

Also, what jet range do you think you were running in before you went home and rechecked your plugs?

Plonking or revving the ring off it or somewhere in between?

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redcloud

· #9 · Jun 20, 2011

Hey Versicolor,

What did you ever conclude with your burn condition? I am running down the same path as you I think where I installed the Brass Rod Modifcation, removed the resistors, added resistive plugs, and the plugs read lean. I have richened them up, and I too am approaching 3 turns, I think I am at 2.5 now?

I did start with 2 full turns and she was a bit sluggish, moved to 2.5 turns, and it is much improved, the balance between the color of the plugs is better, and I am starting to see slight indications of tan. Maybe three will be the magic number?

Just curious what your follow-up might be. One difference in my setup is the local shop did NOT have hte NGK plugs, but had the equivalent resistive style in a Champion Spark Plug.

I am running Stock/Standard Jets on my 79CX500C.

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versicolor

Discussion Starter · #10 · Jun 20, 2011

Well, since I had the bike running pretty good before the mod, I decided to just go back to the aluminum rod and resistor for now. There wasn't really anything wrong with the bike before the mod, I did it just because I thought it would be the right thing to do and I also can't stop myself from doing stuff to the bike. I put the old non resistor plugs back in, re installed the aluminum and resistor and started with 3 turns out because I have the pods, no h-pipe and 90/125 jets. I adjusted accordingly from there. I don't know exactly how many turns out I am at this point but it's somewhere between 2 and 3. My plugs are now a perfect brown, the bike runs great throughout the entire power band and I finally got the idle to settle in nice and smooth. So until I begin to have issues that could possibly be deemed as a result of the plugs and caps, this is how i'm going to leave it. And when I do decide to install the brass rods I will probably rejet to maybe 95/130 to alleviate that lean condition.

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redcloud

· #11 · Jun 20, 2011

thanks so much for the follow-up. I appreciate that you closed the loop for me. I think I am close and might adjust to 3 full turns out to see what happens. This sort of shows how the Brass Rod Mod can affect the burn. I wonder if repeated with an Aluminum Bar, if there would be a difference?

versicolor

Discussion Starter · #12 · Jun 20, 2011

Rick said:
thanks so much for the follow-up. I appreciate that you closed the loop for me. I think I am close and might adjust to 3 full turns out to see what happens. This sort of shows how the Brass Rod Mod can affect the burn. I wonder if repeated with an Aluminum Bar, if there would be a difference?

Not sure about that. I think that copper and brass are a better conductive material than aluminum. Yes try the 3 turns and see how it rides and how the plugs look. I agree with what the guys posted earlier that it's getting a better spark with the brass rod and burning fuel more efficiently. Since I have done away with the H-pipe and airbox I think that if I want to continue with the brass rod then I will have to rejet yet again and adjust the needles from there. Assuming that you have a stock set-up then adjusting the needles should be all that is required for your situation.

redcloud

· #13 · Jun 20, 2011

I thought the same thing until I looked up the conductivity properties of Aluminum...check out the following link:

Materials Conductivity I was shocked at the percent difference between the two...Aluminum would appear to be more than twice as conductive.

I wonder if by using Brass we are doing ourselves a disservice...has anyone ever tried straight up Aluminum?...or copper for that matter!

versicolor

Discussion Starter · #14 · Jun 20, 2011

interesting. Considering the small length and diameter of the rod we are using it probably doesn't really matter what is used in this case. I don't know how you would even be able to tell the difference if you tried aluminum or copper. Maybe i'll throw some aluminum in there just for the heck of it.

redcloud

· #15 · Jun 21, 2011

versicolor said:
interesting. Considering the small length and diameter of the rod we are using it probably doesn't really matter what is used in this case. I don't know how you would even be able to tell the difference if you tried aluminum or copper. Maybe i'll throw some aluminum in there just for the heck of it.

you have a great point with regards to the short length required. I think if you had the bike tuned well, even coloring and carbs in sync with the brass in there, and then changed it up with some Aluminum rods of equal length, ride for a bit and then checked the plug color if there would be any difference.

Another way would be to start with new plugs, run brass, then swap out to a new set of plugs with aluminum, run an equal distance, route, etc and do a side-by-side photo to see if there is any difference in spark color.

curious for sure. let me know if you find anything out...I think some purrty annodized knittin' needles are going to take one for the team in the next couple of days

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stern-69

· #16 · Jun 21, 2011

With the thickness and lenth we are talking about, you wouldnt be able to see a difference if you used a $20,000 Lab ohm meter for measuring superconductors lol. Aluminum is a really good conductor (thats why they made house wiring out of it), but it is brittle when it comes to bending and oxidizes really nasty when it contact with dissimilar metals (why they want to rip it out of house wiring).

Since it isnt a matter of "resistance" of the material here, its best to pick one with the best corrosion resistant properties. Brass will hold up better than copper (even though its a copper/tin alloy) and way better than aluminum (unless every electrical conduction point it touches is ALSO aluminum .... thats why there is a special conductive paste for aluminum to coppr wire joins). Brass is also easier to work with and a lot cheaper that "better choices" (Like a far better resistant metal .. stainless steel).

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