Autolite Plug Gap Single Spark

[Twempie]

Starting my 36k and, thanks to forums like this, will be giving Autolites a try.

I've been reading conflicting reports about the gap on these plugs for our bikes. I have a single spark R1150R and will be installing Autolite 3923 plugs. I found what looked like an Autolite-authored PDF online, which says the gap should be .025". I've read that some riders have set theirs to .03x".

Sorry if this has been answered deep down in the depths of techknowledge 'n banter, but can anyone help me out and shed some more light on this subject?

Thanks.

[towerworker]

I installed Autolite 3923's about 8,000 miles ago in my dual spark 04. I gapped them to .034 and they perform well. I also have a set of 4164's for the secondary plug that I have not installed due to issues with the size of the plug and required wrench. The hex (wrench size) portion is larger than the oem's and the BMW supplied plug wrench won't fit the new plug nor will a standard plug wrench fit in the spark plug cavity on the cylinder---hence they haven't been installed yet.

I've seen gap numbers from .031 to .035 on various posts for the 3923. .034 seems to work well for me. Good performance and economy. I see no discernable difference between them and the NGK's I ran previously. But the price difference seems to be substantial. Some have said the 3923's help with the surging issue that seems to be prevalent with some of the single spark models. I had an 03 prior to my 04 but never had the chance to try them on that bike. Hope this helps!

Wayne

[Twempie]

Thanks Wayne. Everything helps. I'll try the .034 gap first and see how it goes.

I just bought a Twinmax today and will be doing my first throttle body sync. My engine has been noticeably surging lately, even after I did a valve adjust, so hopefully the TBS and Autolites will cure it.

I'm considering a Techlusion FI-1032ST if the TBS/Autolites/valve adjust doesn't work.

[Sunbeemer]

I have a gap of 0.025" in my notes but think I gapped the last set I installed at 0.031, but I don't know why. Maybe that's what they were when they came out of the box, but I know I checked them. They run just fine.

Try some fuel injector cleaner for that surging. A couple ounces (only) of Sea Foam in a full tank has helped my bike run smoother... (I think when they change gas to winter formulation before it gets really cold makes the surging worse.)

[boxermania]

Any gap from .030" to .035" will work well. The most significant thing to the operation of the BMW twins is the TB sync. so set it , take the bike out for a run and re-check it. (for first timers)

In the case of a TwinMax, affix it to the tank while riding to check as you go. Put in new batteries......

[mad1150]

I got PO'd about the Autolite 4164 issue a couple weeks ago.

So I went to the local auto-parts store, bought another cheap deep socket to fit them, and ground it down till it fit on a bench grinder. I know it's not a recommended practice, and it's not pretty, but it works! Besides, it really got me .

If was going to do it again, I'd have a friend do it properly on a lathe.

[boxermania]

Kudos .....there is more than one way to skin a cat......errr.....a Boxer

[Twempie]

Today, amongst other things, I changed the air filter and adjusted the valves, and gapped the Autolites at .025 per the aforementioned PDF. I'll report back after I sync the TBs. Didn't get to the syncing because of another issue (hooking up some PIAA 1100X auxiliaries)... that story's in a separate post.

[mnnden]

I gap mine at 33/34, and have been very happy with the results, I am using the Autolite 3923, but I really think the plug to use is the Autolite 3922, and they will be put in the next time I change, JMOP Den

[chitownrbike]

I have been running the 3922's and they have been better than any others I have tried.
Unfortunately I do not recall how I gapped em............

[Twempie]

Today, amongst other things, I changed the air filter and adjusted the valves, and gapped the Autolites at .025 per the aforementioned PDF. I'll report back after I sync the TBs. Didn't get to the syncing because of another issue (hooking up some PIAA 1100X auxiliaries)... that story's in a separate post.

I've completed most of my 36k service. DIY, with the exception of the fuel filter. I left that to my local independent BMW wrench (who also threw in a TBS for me). So... long story short, new air filter, oil, valve adjust, Autolites 3923 gapped at .032" (I changed my mind about the plug-gap after reading some posts on this forum) along with a TBS and the bike has never ran better - it also seems to sound better. Even without the TBS the bike ran very smoothly, smoother after the TBS (apparently, the throttle bodies were pretty close to spec with 31,500 miles on the clock). I bought a Twinmax but never got to use it this time around, I'm sure it'll come in handy for future endeavors.

I don't really think I need a Techlusion to get rid of the surge after this tune up.

[Biff's R]

In the case of a TwinMax, affix it to the tank while riding to check as you go. Put in new batteries......

Why would you ride around with the TwinMax attached? It sounds like an accident waiting to happen. Take a nice ride 20-30+, and then get a box fan and use the twinmax with the bike on the centerstand. It is a 5 minute job.

[boxermania]

Point well taken Jeff, however, I didn't intend it to mean in all instances. Some of our members are more anal....err.....precise than others and always strive for absolute perfection.

Actually the TB balance on the centerstand might not be all that accurate. We are trying to measure air volume past the butterfly, typically at around 3,000 to 3,500 rpm; I think that I can make the case that because there is no load on the engine, the amount that the butterfly will be open is very small as opposed to the open amount if the engine was under load.

From the standpoint of total flow, or in this case pressure pulses, there isn't much happening, however and think with me for a minute, in the case the engine is loaded (significant opening of the butterfly) the flow past the butterfly has many components, such as the length of the tubes feeding the TB's, their internal restriction, any restriction, side to side by the airbox, etc.

My thought was that after the static TB sync, to affix the TwinMax to the tank and see how it would balance out at constant speed under load, say 4,000 rpm. I'm not a betting man, but would guess that there will be some unbalance between the TB's. Does it affect the operation of the bike, well that will depend on the state of all the other parameters, but on a mass produced unit, I would say yes.

[Biff's R]

Al,
I do throttle up to 3500 to 4000 rpm, and get everything in tune at that mark. There is not as much load on the engine since it is in neutral and not in motion, but I do not think that I could get the TBs synced any better if I were to check it while riding.