Bosch Plugs

[174713]

Quick question- I just replaced my Bosch plugs and noticed the replacements were 2 prong electrodes. The ones I removed were 3 prong. Which is the correct one? 1996 R1100GS is my bike.
Thanks,
Charlie

 

[PGlaves]

Quick question- I just replaced my Bosch plugs and noticed the replacements were 2 prong electrodes. The ones I removed were 3 prong. Which is the correct one? 1996 R1100GS is my bike.
Thanks,
Charlie

My recollection from 25 years ago is that the original plugs were 3 ground electrodes but the specification was changed to 2 electrodes very soon after, maybe as early as 1995.

 

[174713]

My recollection from 25 years ago is that the original plugs were 3 ground electrodes but the specification was changed to 2 electrodes very soon after, maybe as early as 1995.

Hmm, that could explain why the dealers can’t explain where the 3 ground electrode plugs cam from. Another reason these forums are such a great resource, thanks Paul.
Charlie

 

[PGlaves]

Hmm, that could explain why the dealers can’t explain where the 3 ground electrode plugs cam from. Another reason these forums are such a great resource, thanks Paul.
Charlie

I am positive that Voni's '94 (built in March of '93) R1100RS came with triple electrodes. They didn't work very well because spark masking was happening. That is when the position of the electrode masks the spark from the incoming fuel charge. (Look up "spark plug indexing). The dual electrode plugs improved things but Autolite 3923 single electrode plugs became very popular. They didn't last as long but were cheap and easy to replace every 12K miles during a major service.

 

[174713]

I am positive that Voni's '94 (built in March of '93) R1100RS came with triple electrodes. They didn't work very well because spark masking was happening. That is when the position of the electrode masks the spark from the incoming fuel charge. (Look up "spark plug indexing). The dual electrode plugs improved things but Autolite 3923 single electrode plugs became very popular. They didn't last as long but were cheap and easy to replace every 12K miles during a major service.

Thanks again Paul.
Charlie

 

[walsj1024]

Paul,

I would like to try the Autolite 392 plugs in my 2000 R1100 RS. Would you recommend using the same gap as the original plugs?

I am positive that Voni's '94 (built in March of '93) R1100RS came with triple electrodes. They didn't work very well because spark masking was happening. That is when the position of the electrode masks the spark from the incoming fuel charge. (Look up "spark plug indexing). The dual electrode plugs improved things but Autolite 3923 single electrode plugs became very popular. They didn't last as long but were cheap and easy to replace every 12K miles during a major service.

 

[PGlaves]

Paul,

I would like to try the Autolite 392 plugs in my 2000 R1100 RS. Would you recommend using the same gap as the original plugs?

Yes. The electrode structure is similar. With multi electrode plugs only one sparks at a time - the one with the least resistance. As one wears another takes over.

So given the similar structure the same gap works fine.

 

[walsj1024]

Paul,

Thanks, I did mean the 3923 plug, just typing too fast in the morning.

John