How lean is too lean?

[Varastorm]

Boredom set in on the dual carriageway on my way home after a 90 mile Snowdonia ride last weekend, so I decided to do some constant rev runs & cut the ignition & clutch in at various engine speeds.

Performance wise, all's good apart from the popping & banging on the over run, which does sound quite good tbh. But there are no running issues, surging etc.

I did two, both at cruising speeds. One at 4000rpm & one at 5000rpm.

Pic 1 @4000rpm.


Pic 2 @ 4000rpm.


Pic 3 @ 4000rpm.


This is the 5000rpm pic's.

Pic 1 @ 5000rpm.


Pic 2 @ 5000rpm.


Pic 3 @ 5000rpm.


Pic 4 @ 5000rpm.


I have read loads about reading plug colours, but more & more I hear about the combination of iridium plugs & newer fuels making reading plugs harder & harder.

From what I've read & seen, I was going to file some more from the needle area that corresponds to the 4-5000rpm to richen it up a little.

But when I pulled the bike apart & lifted off the tank the thing is close to 2/3 full after 90 miles

The tank holds 25 litres & I used to get around 120 miles before the reserve light shows from full leaving me around 4.5 litres.

So what I did was look into the cylinder through the plug hole at tdc to see if there was any sign of damage to the piston. None could be seen so I am putting it back together to see what this set up will give fuel wise.

What so you guys recon?

Sorry for all the photo's, just wanted to give all angles

[fabiostar]

maybe im a bit old school but id call that on the limit .. if it was mine id like a little more colour than that

[darkember]

maybe im a bit old school but id call that on the limit .. if it was mine id like a little more colour than that

I beg to differ they don't look bad at all. Light tan or grey indicates a good engine. What are the state at the end cans any soot deposits or is it clean to the finger test??

[bigtwinthing]

too lean i reckon

[Varastorm]

maybe im a bit old school but id call that on the limit .. if it was mine id like a little more colour than that

I beg to differ they don't look bad at all. Light tan or grey indicates a good engine. What are the state at the end cans any soot deposits or is it clean to the finger test??

Well, that's the odd thing, the end cans show signs of soot.

Wipe them & you'll get blackened hands (I did clean then prior to the run on Sunday btw).

Not a lot of soot, but enough to confuse me with my diagnosis of too lean.

I am thinking of taking it for another dyno run but I am dying to know how much I'll get out of a tank with this setup of running filed dj needles with the clip in groove 1, at the top.

[popkat]

Soot in the pipe can be too rich on the cruise, lean off the needles for improvement or see if the emulsion tubes are worn.. The plugs look a bit white but if it still pulls well through all revs it's shouldn't be too lean although if mine i'd go up one size on the mains for piece of mind.

Soot on the pipe could also be a sign of valve stem seals leaking or oil scapper rings going.



.

[Varastorm]

Soot in the pipe can be too rich on the cruise

The plug pictures above are from a cruise state Popkat, 65'ish @ 4000rpm & 80'ish @ 5000rpm

although if mine i'd go up one size on the mains for piece of mind.

I've had no issues with the mains, the sheets from the dyno afr seems spot on.

I am with all you guys though, it does look lean.

But if it behaves through out the rev range, bar pops'n bangs on the over run & gives around 45-50 to the gallon What do you do

I used to get around 30'ish running Hawks setup

[Saintsman27]

M8tey your first word " Boredom" is a clue to all of this .. the plugs look
spot on ... if it works leave it ..

[NZSpokes]

That would worry me. A lot. Whats it like at part throttle at high rpm? If it goes flat then you are close to losing a valve.

look at them with a magnifying glass. See if there are any little silver spots. If so your pistons are melting.

[Pete.L]

you could always raise your needles 1/2 mm and see how it feels then.
They do look on the slightly weak side but not by much.
Get diagnostic run done if you are really worried and I would have a good check of the rear intermediate joint of the exhaust to see if it's leaking. The banging and popping could just be an exhaust leak which needs sorting.
Mid to high 40's on a gentle run is quite normal for a well sorted (standard) bike. I would be far more worried if I could only get 30. Whilst slightly rich is better than slightly lean too rich is just as bad.

Pete.l

[kenmoore]

Those plugs look lean to me, however if you like the way your bike is going what is the worse that can happen?

From my experience there is no better diagnosis tool than the old butt dyno.

After all you know your bike better than anyone else!

Ride on and enjoy, I found the comment about reading plugs with the latest crop of fuels interesting.

Here are my plugs and they are a stark contrast to yours as you can see.



The one on the left is the front cylinder and the one on the right is the rear cylinder.

The plugs were removed after a rather vigorous ride.

[TheGingerBeardMan]

I would say yes, they are running too hot. Far too white on the ceramics.

To quote NGK:

A clean white Insulator / Ceramic:

This is often caused by over advanced ignition, timing, or poor engine cooling efficiency (scale, stoppages, levels etc), a very lean air/fuel mixture, or a leaking intake manifold. Also check for vacuum leaks or sticky valves. When these conditions prevail, even a plug of the correct heat range will overheat.

Your plug colour is between the 7 and 8th last on the chart.


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For plug colour on any bike, I'd prefer to see Kenmoores each time.

The ceramic should look like a mild cup of tea. Not milky white, but not dark "stewed" tea. Again, Kenmoores look pretty damn good.

I take it both of you are using the Iridium NGK plugs? Personally, I haven't pulled my new plugs to check the colour. I just replaced the old NGKs with the Iridiums with a "FAF" attitude (Fit and Forget). They've been in for about 2000 miles, and will only get examined when it comes to another oil and filter change.

[TheGingerBeardMan]

.
Having said all that - the charts are for the "old style" ceramics on the "old style plugs".

I wonder about the new iridium and split-fire plugs - with new advanced ceramics. It does raise the question: Do the new advanced tech plugs remain a paler/white colour, due to the ceramics ability to withstand higher "racing" temperatures? Or, does it not make any difference? Do formula 1 racing cars, or MotoGP bikes all stick to the "tan coloured plug" chart, or should we be looking to change the chart to coincide with new technologies and advances in spark plug design and function?

Yes, at the end of the day, the internal combustion engine is pretty much the same, and the current spark plug chart is fine for covering bikes from the 1940s to the late 1990s/2000s. But, it still makes me wonder about the "new plugs" on the market. Aside from price, do they really make a world of difference to us road users? Are they a gimmick (as in not much use or difference unless racing on a track), or should we all just be sticking to OEM spark plugs, knowing that's what Mr. Honda recommended the bike was fitted with/made to run on when it left the factory.

I dunno.

[NZSpokes]

.
Having said all that - the charts are for the "old style" ceramics on the "old style plugs".

I wonder about the new iridium and split-fire plugs - with new advanced ceramics. It does raise the question: Do the new advanced tech plugs remain a paler/white colour, due to the ceramics ability to withstand higher "racing" temperatures? Or, does it not make any difference? Do formula 1 racing cars, or MotoGP bikes all stick to the "tan coloured plug" chart, or should we be looking to change the chart to coincide with new technologies and advances in spark plug design and function?

Yes, at the end of the day, the internal combustion engine is pretty much the same, and the current spark plug chart is fine for covering bikes from the 1940s to the late 1990s/2000s. But, it still makes me wonder about the "new plugs" on the market. Aside from price, do they really make a world of difference to us road users? Are they a gimmick (as in not much use or difference unless racing on a track), or should we all just be sticking to OEM spark plugs, knowing that's what Mr. Honda recommended the bike was fitted with/made to run on when it left the factory.

I dunno.

Im going to try some copper plugs if I can find them. I suspect iridium ones are to reduce the number of changes. Copper from what Im told gives better power.

[Watty]

Lloydie is the plug specialist!!!!! Butt plug