Plug Chop - Please help me analizing results..

[Adamastor]

Hi there!

I went for a ride with some friends yesterday, the bike was ok but my friends told me that the left side exhaust had some white smoke when I was accelerating hard.
This means too rich mixture, right? That adds to the fact that my left side exhaust is darker than the right side one...

Since at hard acceleration we mostly don't use the idle settings, I decided to drop the needle one notch. Engine seems to behave the same, I don't know exactly on what notch is the right side (the screws are blocked and don't want to mess with them unless I really have to).




I made this plug chop after riding about 15km at 4500/5000 rpm... what do you think of these plugs? The whiter one is the left side plug, I believe some of the debris you find there are deposits from a former too rich situation.. Maybe I should buy new plugs to test this right?

Please let me know what you think

Regards,

Sergio

[Bob_Roller]

You need to have clean spark plugs to get an accurate reading with your method .

If it's white smoke, more likely to be oil rather than a rich mixture .

[Lucky_Lou]

You need to have clean spark plugs to get an accurate reading with your method .

If it's white smoke, more likely to be oil rather than a rich mixture .

Looks like theres heavy carbon on the outer edge of the plug im with Bob i  see a set of piston rings in your near future.
Lou

[Barry]

Carbon around the base ring of a plug is not a good indicator of mixuture as this surface is at much the same temperature as the combustion chamber in the cylinder head and we know that gets carboned up even when the mixture is ok.

The plug insulator and electrodes are better indicators of mixture although they are said to be harder to read since unleaded fuel was introduced.

Ideally new plugs should be used and even better if your going to start the engine on choke wait until the engine is warmed up a bit before putting the new plugs in.

[Mike V]

I would agree, and the plugs don't look all that horrible to me other than the inconsistancy.  I would check your valve settings, maybe a compression test (hot) will tell you more than you think, timing check and throw in some fresh plugs and do a brisk 20-30 minute ride and recheck the plugs immediately without idling for too long. let us see what they look like after that.

Are you saying the carb metering rods are set at different notches? I would move them back to the original (like) settings before continuing your testing as it may give you a false reading at the plug. Is your partner seeing white smoke from the exhaust when you accelerate after decellerating? If not I would agree with Bob and Lou maybe towards rings. If white smoke after decelleration you may be getting some oil past your valve guides. Just my thoughts, interested to hear others.

What year and how many miles? Oil consumption?

[Adamastor]

Hi and thanks for all teh replies... now for some more info:

The bike has unknown kms but I assume at least 250.000/300.000km since it is a former police force bike.
Both pistons have new rings, smoke that they saw was at heavy acceleration, not on deceleration.

About the carbs: this is a tricky part.. the left side carb is NOS, the right side is the original one. Why did I buy a new left side carb? Because I could never fine tune the mixture screw (best position was completely in and still would foul plugs).
With the new carb I can see effect on the mixture ring (I tune it for the higher revs by ear).

I really dont know the position of the needle on the right side because, as I explained before, the screws are blocked and I dont really want to brake them without a really good reason to go in there.

Both these plugs are half an year old.

This test: I was riding on the highway at 4500/5000 rpm and pushed the kill engine button and coasted to a gas station, so these results are not influenced by the idle circuit.

I guess I might buy a new pair of sparkplugs this next week and re-do this test. But apparently by these results I don't think there's any problem of either fouling a plug or holing a piston.

I have been reading this article:
http://www.strappe.com/plugs.html
and white insulator is normal because you should only see a black ring on the bottom of the insulator (deep inside the sparkplug).. and that's very hard to photograph

One of my friends filmed part of our ride, but unfortunately I could not see any smoke (and its colour)... if you care to see, it is here:
http://vimeo.com/11782242 You can see me passing by at 2:08 and at 4:56 minutes..

Regards,

Sergio

[Barry]

That's a good article on plugs. I  have previously tried to read the "mixture ring" at the base of the insulator and it 's very very difficult. You need good light and a magnifying glass or in my case a stronger pair of reading glasses that I keep in reserve for close up work.

I've also tried to photograph the mixture ring with mediocre results. Here's a BP7ES as it came out at a service not after a "plug chop". It has a little carbon on the base ring and good colour on the insulator and side electrode. I think you can see some carbon on the mixture ring just to the right of the side electrode but it does not extend up the insulator at all which according to the article reads as OK certainly not excessively rich. I don't think the photo is really good enough to see this well. I haven't got it quite straight on for a start.[img][/img