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1100rt spark plug question

HOUKSTER

New member
Finally found the Autolite 3923 plugs after ck'g Autozone and O'reillys at Pep Boys.
Got the double platinum for longer life.
Question is on the gap. With the stock plugs, dual prong it's only .031, but the Autolites are about .044 out of the box. For you guys who have installed these, did you leave that gap or change it?
Tks.
 
Mine came the same way. I don't know if it is best but I try to have the face of the tang parallel to the top of the center electrode. Given the amount of movement needed I found that difficult, one plug needed a slight compound bend, the other plug ended up with the ground extended well beyond the center electrode. I used them but didn't like what I went through.
 
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Gap is determined somewhat by what the ignition system can crank out (along with fuel mix, compression, etc.). Cars' ignitions are historically much more robust than bikes'. If you can't reliably and repeatedly light the fires, it ain't gonna run right.

Been a while, but I recall setting mine to .032 with zero issues, and let 'em wear - which they did quite slowly, and better than the factory Bosches (which I've never had "fine running" with anyway).

Note that on some auto plugs, the manufacturer clearly intends that the gap is NOT to be changed - not only is the ground electrode Quite stiff, but it can be really easy to crack the center porcelain.
 
Fine tip spark plugs can, in theory, be gapped larger for the same ignition. Due to the materials and geometry, you should be able to jump the same gap with fewer volts. Therefore, you can increase gap to get a larger spark at the same voltage.
 
With my 1150RT now running really well on a richer mixture, I'm going to switch back to the stock plugs and see how that goes. And because I don't put much mileage on I'm thinking of gaping at 0.035".
 
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With my 1150RT now running really well on a richer mixture, I'm going to switch back to the stock plugs and see how that goes. And because I don't put much mileage on I'm thinking of gaping at 0.035".

Why bother? Stock plugs are much more expensive than the alternatives that seem to work better in most cases anyway.
 
Why bother? Stock plugs are much more expensive than the alternatives that seem to work better in most cases anyway.

Mainly because I want to see if there is any discernible difference between the autolites which I have now and the NGK/Bosch, with the richer mixtures I run now.
 
Mainly because I want to see if there is any discernible difference between the autolites which I have now and the NGK/Bosch, with the richer mixtures I run now.

If it is running fine now, how will you know if it improves with a swap to the high priced plugs? I've run copper Autolite plugs in my 95 r1100r for the last 6 years without any trouble. Although I don't put a lot of miles on them, every year I put in a new set, the old ones look perfect. They cost about $1.50 each at WalMart.
regards,
Mark
 
If it is running fine now, how will you know if it improves with a swap to the high priced plugs? I've run copper Autolite plugs in my 95 r1100r for the last 6 years without any trouble. Although I don't put a lot of miles on them, every year I put in a new set, the old ones look perfect. They cost about $1.50 each at WalMart.
regards,
Mark

That's a good question. I'm not expecting any improvement, I'm more curious if I will be able to tell the difference at all. I'm sure there's a reason why BMW specified dual electrode plugs. Mostly my curiosity at work.
 
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