Misc: Ignition Spark Plug Query

[kerry]

Been given by a kind retired Vincent expert boxes of NGK BP5ES and BP5EVX are these suitable for a twin ? any information appreciated.
The EVX ones look costly.
Thanks

 

[Bogage]

They seem hot to me, I use 7 or 8... if I had oily plugs maybe I would use a 6, but 5 seems hot...?

 

[Bogage]

BP7ES or BP8ES are the plugs I use, the ES means the electrode is extended deeper into the cylinder, they normally call for the BP7S or BP8S if I am not mistaken, the ES just allows for the spork to be deeper into the cylinder... I am sure that there will be other input that may be more accurately explained.

 

[kerry]

Appreciated, but, I did read than in an older well used Vincent 5 would burn off soot etc better ? Does it matter if a plug is hotter ?

 

[Bogage]

This is true, but you don’t want to burn the piston. As I said, I am merely a peon in comparison to many who lurk here. But I have heard of burnt pistons and running too hot so if the plugs look good with 7 or 8 I would not run hotter.

 

[Bogage]

BTW, lower number is hotter with NGK

 

[LoneStar]

Yes, very risky to run a too-hot plug. Bikes vary, but I run an NGK 6 or 7 range - platinum or gold-palladium, for better spark during kickover with a magneto. For BP6ES, it's the 'P' rather than the 'E' that indicates projected tip.

 

[kerry]

I am no expert , far from it but was told when given these that they are good for slightly worn twins and as twins do not run hot like say a comet then 5s should be OK and being EVX are less liable to foul, I have bought duff copies of NGK and Denso plugs so thought worth a try with these but maybe not ?
Appreciate the advice.

 

[Bogage]

Yes, my bad, it would be a B7ES or BP7ES, the P for protruding. Kerry, you will find many opinions to be sure. It is possible that you will be fine, but perhaps taking the heat range in a larger perspective will enhance your understanding. Cheers

 

[kerry]

Thank you, seems the best plug is B6ES or the original KLG FE ones. 20 thou too.