Is my bike running lean?

[Les Wassall]

How do I tell if the bike is running lean or not, I have just replaced my spark plugs and removed a pair of Brisk, the centre bit on one seamed a bit darker than the other, both were a sand colour but the darker one seamed to look like it was starting to burn, were the spark makes contact.
The plugs have been in for 8K and seem to splutter on starting, not as sharp as they were, once warm run ok, so replaced with Splitfire to give them a try.

 

[Strangelove]

If the bike's running lean the plugs will be white. The whiter the leaner and hotter running.

 

[Les Wassall]

White on the centre electrode or the metal tips round the bottom, these Brisk look a little different to a standard plug.

 

[The Mechanic]

Get the true picture.

Les to get the true picture you have to carry out a plug chop. This entails riding fairly 'briskly' (sorry couldn't resist that) at about 50-60 mph in third or fourth, then pull in the clutch and kill the ignition immediately DO NOT let the clutch back out until you have stopped. Obviously this is carried out some where on a quiet road. Now you can pull the spark plugs and look at the colour, this will be the actual running colour and not the idle mixture colour/foul up that most people think is the indicator to mixture diagnosis.

Light biscuit colour is fine, white in the centre around the electrode with darkish grey around the perimeter is also ok, and this is what you will probably see.

At normal running speeds the combustion temperature will be around 2,000 - 2,500 degrees C and the plug is almost self claening at this kind of temp. Whereas at idle and blipping in the garage will just produce a confusion of irregular combustion deposits.

Nip into any good carparts shop and ask if you might look at there spark plug reference books, they nearly all have colour photos of what the plug should look like for correct mixture etc.

Brisk plugs produce a broader spark (flash) and so tend to look slighltly different to the more 'normal' type of plug.

Hope this of use to you .

 

[Chris G]

Re: Get the true picture.

Les to get the true picture you have to carry out a plug chop. This entails riding fairly 'briskly' (sorry couldn't resist that) at about 50-60 mph in third or fourth, then pull in the clutch and kill the ignition immediately DO NOT let the clutch back out until you have stopped. Obviously this is carried out some where on a quiet road. Now you can pull the spark plugs and look at the colour, this will be the actual running colour and not the idle mixture colour/foul up that most people think is the indicator to mixture diagnosis.

Light biscuit colour is fine, white in the centre around the electrode with darkish grey around the perimeter is also ok, and this is what you will probably see.

At normal running speeds the combustion temperature will be around 2,000 - 2,500 degrees C and the plug is almost self claening at this kind of temp. Whereas at idle and blipping in the garage will just produce a confusion of irregular combustion deposits.

Nip into any good carparts shop and ask if you might look at there spark plug reference books, they nearly all have colour photos of what the plug should look like for correct mixture etc.

Brisk plugs produce a broader spark (flash) and so tend to look slighltly different to the more 'normal' type of plug.

Hope this of use to you .

Les,

this is wot I did, the best way to get a "snapshot" of the mixture.. I did it along Moreton flats and then freewheeled into the hall to drop the plugs out, qick digital piccy of the plugs, then after putting it all back together up to my house to drop off the pads and bits!

 

[Les Wassall]

for the info, I will give it a try.

Chris, I've just PM'd Neil as the bits have not arrived yet, let you know soon as.

 

[andy]

This might be of some use.


http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

 

[The Mechanic]

Ah so Confusus(?) he say.....Blimey!

Ok so is ok ok, or it just ok with a bit of not so good ok and is that alright to keep running on. But if its ok but not so ok then is that good but not ok to keep running on?

However when the plug is good with a little bit ok is that not so good as just plain ok?

When is almost too hot ok but borderline not ok too hot not ok?

Ok so I take the urine ....sorry ok ..I couldn't resist.....ok.


P.s do you realise that some people will look at your pics and start to question every colour known to man because they will think they can see it in their plugs....clear some space on this site.

 

[andy]

That's ok