Opinions on plugs

[DB90]

Anyone care to give some feedback on my plugs?

I've looked at the online plug reading pictures but nothing beats some real (or semi real) life feedback and opinions.

From what I've seen on charts, the left one looks pretty alright and the right one looks a bit lean but possibly within the ok range?

 

[member28833]

Approx how many miles are on those clean looking plugs. RT. tad lean but they look very new

 

[DB90]

Approx how many miles are on those clean looking plugs. RT. tad lean but they look very new

There's just about 200 miles on them at the moment. They were brand new.

 

[member28833]

I think right in the middle of the Lft. Dark chocolate brown and the Rt. White chocolate color is the target.
Very close though.
Mixture screw adjustments may hit it.
There is a tech procedure which describes to turn those individually finding best position by the idle speed changes.
Search , on my phone here

 

[DB90]

I think right in the middle of the Lft. Dark chocolate brown and the Rt. While chocolate color is the target.
Very close though.
Mixture screw adjustments may hit it.
There is a tech procedure which describes to turn those individually finding best position by the idle speed changes.
Search , on my phone here

I think that is the Target too. The left one is close! Mixture adjustment is definitely what I need to adjust. I had actually adjusted them to where they are at right now because they were running too rich. Alittle more tweaking and it should be money!

 

[gggGary]

Just opinion, how was the plug chop done? But the RH looks about right the LH is a bit rich.

 

[DB90]

Just opinion, how was the plug chop done? But the RH looks about right the LH is a bit rich.

Just to make sure that I understand what a plug chop is, it's pinning the throttle and running through the gears. Correct?

If so, I didn't actually do that. I've just been riding the bike back and forth to work. Which is mostly back roads and highway riding.

 

[gggGary]

Guess you want to figure out why they are different. Fuel level in float bowls?
Pic of the bike?

 

[member28833]

Mornin’ yes the Lft does seem a little black sooty ? How does your bike feel when you run it in to work and around.
Lucky cool commute I might say ..
(Spark wise)

 

[grizld1]

DB, you can't get much useful tuning information from a plug that's been used all through the range from idle to WOT. A plug chop is useful only for testing the mixture at WOT to select main jets. A plug chop has to be done on new, clean plugs at a location at which you can hold the motor at full throttle for at least 30 seconds and preferably a full minute or more. At the end of the run the throttle is held open while the rider disengages the clutch and cuts the ignition, so that all that shows on the plug is the full throttle condition.

Alas, much myth and bullshit has accreted around the topic of plug reading. For the straight skinny, go to www.strappe.com, click on "Tech topics," click on the spark plug icon, and have a read through what Gordon Jennings, the old master, had to say on the topic.

That having been said, your best results for street tuning will be obtained by observing how the motor behaves and jetting accordingly.

BTW it's pretty much normal for the left plug to look a little bit darker than the right on these motors if the plugs have been run at highway speeds, because the motor runs a tad hotter on the primary side.

 

[Paul Sutton]

Oh, its opinions you want! Well then! I would check fuel level, like Gary suggested, with a piece of clear tubing while the carbs are still mounted. Make sure there are no air bubbles trapped where the tube meets the carb; I suggest that with the petcock off attach the tubing and fix it firmly in place so it cannot move. Open the drain valve on the bowl and let the tube fill but keep tapping the tube until there are no bubbles trapped. Then open the petcock and see where the fuel levels out at.

If levels are fine then I would just open the mixture screw 1/8 turn for the lean plug and close the mixture screw by 1/8 for the sooty plug. Do some riding, about 20 miles preferably out of town but taking it easy not to run the bike too hard if you suspect lean, and then check to see if anything has changed. You may have to repeat the 1/8 adjustment exercise again for one or both plugs.

I am glad you asked for opinions because I have some more. When you use the online colour guides the sets with about 20 pictures are really great, but they show you to much information with many colour scenarios being acceptable. My simplified interpretation is simply the porcelain should not be bright white or as dark as your left plug. Also the ground strap should be clean for 2/3 of its length. If you look carefully then you often see a line on the ground strap where it is heated clean to. Your right plug looks a bit too lean as the strap looks completely burned clean.

In my RD250 days any colour except white was good and usually they were like your sooty plug. If in doubt as to what is too sooty then carry a spare set of plugs with you and if the engine starts to splutter, stop and change the plugs, which was quite common on my RD250.

If you have just rebuilt your engine then the sooty plug could be due to residual oil in that cylinder and it can take 20 - 50 miles to burn that oil off completely.

Good luck.

 

[DB90]

Awesome. Thanks for the input guys! I think I'll just mess with the mixture screws a little bit. That's how I got to these results. The bike seemed to be too rich on the mixture screws before I leaned them both out a touch.

Here's a pic @gggGary

20190803_185638-1

• DB90
• Aug 21, 2019

 

[member28833]

Got it, your mufflers are too restricting !

Cool tail light & signals

 

[DB90]

Got it, your mufflers are too restricting !

Cool tail light & signals

Haha! Believe it or not, there IS baffling inside those pipes. Not much though, they're only about 6 or 7 inches long.

 

[5twins]

When reading plugs, what you want to look at is what's called the "mixture ring" or "smoke ring". This will be a ring of color at the bottom of the porcelain. Ideally you want it at the bottom coming maybe 1/8 to 1/4 up the porcelain .....

Your plug pics don't show down inside the plug so we can't really see the "mixture ring", but from what we can see I'll have to agree - your left plug looks too rich, right one maybe a tad lean. But, have a look down inside that right one at the "mixture ring".

As an experiment one time, I set my needles one step richer. My plugs looked good before that with the "smoke ring" down at the bottom of the porcelain. I took a ride for a few miles, cruising in the midrange, "on the needles" so to speak, then pulled the plugs. The "smoke ring" had climbed way up on the porcelain now, covering 2/3 to 1/2 of it.

 

[XSLeo]

I agree with what Paul Sutton said about the ground strap. I look to see how much is burnt clean. I like the line to be almost to the bend. If on the bend a bit lean, If not to the bend a bit rich.
A lot of those plug charts were made back before ethanol gas. Ethanol gas burns a bit cleaner, so you don't get as much color on the plugs as you got with non-ethanol gas.
Used to be a light tan on the insulator was right. To light=lean, to dark = rich. Easier to read.
Leo

 

[DB90]

I agree with what Paul Sutton said about the ground strap. I look to see how much is burnt clean. I like the line to be almost to the bend. If on the bend a bit lean, If not to the bend a bit rich.
A lot of those plug charts were made back before ethanol gas. Ethanol gas burns a bit cleaner, so you don't get as much color on the plugs as you got with non-ethanol gas.
Used to be a light tan on the insulator was right. To light=lean, to dark = rich. Easier to read.
Leo

If it makes any difference, I am running non ethenol gas.

 

[5twins]

As far as plug color goes, I don't think it's so much the ethanol but rather unleaded vs leaded. Those old charts came from leaded gas days. Today, shades of gray are very common instead of brown.