NGK Spark Plug, Gap, and Pictures

[probablecause]

I was told that the replacement plug for the 295 (Year 1999) was a NGK BPR4ES. So I went out and got to replacement ones (E3.46). However they are about a 1/4 longer in the neck of the ones I pulled out of my motor. The ones I pulled out are NGK BR8ES. Now, if that is the plug that is supposed to be in my 295, then so be it. However, I just want to make sure that is because the new plugs are 1/4 inch longer which I don't think will work.

[scottyb]

You were told correctly. The gap is .028 -.030

If you have any doubt just put one in and rotate the engine by hand.... if the piston hits the plug it will stop dead.

[probablecause]

Originally Posted by scottyb

You were told correctly. The gap is .028 -.030

If you have any doubt just put one in and rotate the engine by hand.... if the piston hits the plug it will stop dead.

Ok, then the question would be: What effect would the shorter BR8ES plug have on the performance? It is almost a 1/4 inch shorter than the BPR4ES.

[scottyb]

I am not a plug expert but I was told that a shorter reach on a plug would result in a lower combustion chamber temperature & in some cases a cooler running motor.

I know there has to be a down side ~ there always is...... lets wait for an expert

[probablecause]

Ebay says BP4ES

[crash12888]

BPR4ES is the correct plug for the 295 Robin engines. I would recheck the plug numbers they gave you as a replacement or just get BPR4ES plugs.

Also, Looking at the pictures you need to move the plugs so the bases are even where the compression ring sits.
You might find the depth of the electrodes and ground tabs are the same then.

[gornoman]

Originally Posted by crash12888

Looking at the pictures you need to move the plugs so the bases are even where the compression ring sits.
You might find the depth of the electrodes and ground tabs are the same then.

Actually, the situation worsens if you do this.

[probablecause]

Originally Posted by gornoman

Actually, the situation worsens if you do this.

Yes it did. The threads are the same but the top part is much longer.

[crash12888]

Originally Posted by gornoman

Actually, the situation worsens if you do this.

Oops, it does indeed!
Not sure why the 8s are in they are what Seadoo uses in there water cooled jetski engines.

[invalidsession]

Originally Posted by gornoman

Actually, the situation worsens if you do this.

Are you thinking of the old racers trick of indexing the spark plugs so that the ignition source of the plug directly faces the exhaust valve Gorno ? I spent hours shimming plugs to create that when I raced motorbikes and never noticed a difference worthy of a nuns fart although some swear by it. (Not the fart btw)

Chris.