Do dual sparks plugs on a cylinder help?

[scottyintex]

Ok........my ignorance is showing again....explain this thing to me. I am in the HEB parking lot...run across another airhead rider on a R100/7...We are bragging on the merits of our machines or lack there of. He proudly points out that he has dual spark pugs on each cylinder. He claims it makes the machine start better.....run better. Ok, to me it seems a bit of over kill. I firmly believe if it’s working really well........don’t fix it. Odds are you will just mess it up. Do dual plugs really help? Or is this a bit of mumbo jumbo voodoo... looks impressive but does not really do that much?

[Rob Valdez 79 R65]

They help on high-performance boxers (I forget the details without looking it up), but I don't think our R65's would benefit.  It would have been recommended to you when you had your rig built, if it was necessary.

I believe it comes with high-compression and a larger bore, which increases the area in the head and the 2nd spark plug helps to burn the fuel mixture more efficiently. (shorter flame path/travel)

[Semper Gumby]

Define "Help" please.

[nhmaf]

They do reduce the tendency for pinging on lower grade/octane fuel under various load conditions, especially if the engine piston's are large and/or high compression.  The R65LS cylinders with an original CR of about 9 or 9.5:1 seems to be about at a point where it doesn't seem to make much difference, at least with the typical gasoline grades that we get in the US.   If the fuel quality were a bit worse, then it might be more practical to consider doing this on the R65.   Many of the earlier R90 and R100 bikes with 9.2:1 CR or higher cylinder and piston setups seem to be much less sensitive to fuel grade variance and pinging/detonation with dual plugging applied.   Of course, this adds some more complexity to the system.

The Honda, Kawasaki, and Suzuki V-twin cruisers pretty much all use dual plug setups on their fairly high compression engines of 700cc and over.   Smoother running and less finicky carburetor setup and improved emissions seem to come with a properly setup dual spark system, all gained from having the 2nd spark source (faster and more complete combustion across the volume of the cylinder)

[GrimReaper]

Robert Fleischer a.k.a. Snowbum said that dual pluggin is great for touring and in the same time reduce the performance

[Motu]

My XLV750 had dual plugs....and dual CDI units will two ign circuits....and 4 ign coils.A lot of stuff to go wrong.But it seemed to go well....just as well as any single plug bike I've ever ridden.

[steve hawkins]

When I was investigating the tuning of my R65, most tuners were recomending dual plugging.  

I have heard that in itself it does not achieve a great deal, just making the burn quicker/more efficient, but it is necessary/recomended to get the best of other tuning activities.

As a result of the high cost and limited gain from tuning an R65, especially a pre 81, I did not bother.

Cheers

Steve H

[Ed Miller]

I can already run regular grade gas in my R65 without pinging, so I don't think there would be any benefit from dual plugging.  Mine is an '81.

[montmil]

I sort of believe that most of the beneficial points regarding dual-plugging on Airheads are advanced by those selling dual plug services and parts plus those riders that have recently spent a large sum of money. [smiley=2cents.gif]

Monte

[GrimReaper]

there is a lot info about dual pluggin'
http://bmwmotorcycletech.info/dualplugging.htm

[Andrew]

From my sports car experience, especially with high-domed pistons (typically in hemi chambers) that "block" the flame front progression they can help give better combustion, and on four-valve heads in which you can't place the spark plug centrally (optimally) they can help. This latter not applicable to R65s.
Andrew

[Andrew]

I should say four-valve and large-valve heads, like Alfa GTA.
Andrew

Andrew, you can click on 'Modify', and add to a post you have already made. [R. Valdez, mod.]

[Barry]

Another controversial topic that's relevant here is "spark plug indexing".  The idea is to position the plug so that the earth electrode does not block the path between the spark and the main body of the combustion chamber. On an airhead that means the earth electrode  pointing vertically upwards.
Advocates of spark plug indexing mark the position of the earth electrode on the outside of the plug then use crush washers of various thickness to ensure correct orientation when the plug is torqued up.

The idea makes some sense but the advantages are probably marginal otherwise everyone would be doing it.

[Dizerens5]

Haha Barry in a totally different area that would be familiar - many who like me have had a laryngectomy (removal of voice box due to cancer) and breathe by neck opening will have a "Blom Singer valve", an artificial speaking aid, this has a tag which is taped in place to hold the valve in the correct position for good operation (the tape needs changing every couple of days).Sounds just like indexing a spark plug! Btw I never asked the surgeon if I could continue motorcycling, I just did it anyway and have not had any trouble in eight years so far. I wonder if the R65 site has any other "larries"?

[scottyintex]

Well....thanks one and all. SinCity I read the article several times....even understood some of it. However, I am going to stay stock on number of spark plugs on the R65. I don't see it as making much difference. However....if I still had the R27....kick start ...I would have been tempted.