Twin Spark

[MR.E]

Hello

Whilst i've been buying parts for the race/bonneville bike, getting excited with all the parts arriving, i've seen a few bikes kicking about with twin plugs on the cylinder heads.

1, Has anyone done it??
2, What will be the benefits of it??

Thanks

[steve hawkins]

Whilst not adding much in the way of power on their own, they certainly always seem to be included in the professional tuners list of mods.

When I was dabbling with the idea of tuning mine, it seem to be almost the first thing on the list of the 3 tuners I spoke to. Followed by more CCs, A higher compression ratio, a different cam and then carbs.  The tuners I spoke to were

Andrew Sexton
Jim Cray
Difazio

Cant remember much detail though, as it was some time ago and I wimped out (due to cost).  I know it was far more expensive than what I paid for my R100.

Rev. light

[Barry]

I don't think it's been done very often to R65's probably because it's "only a 650" and the benefits should be greater on the bigger bore R100's where the flame front has further to travel.  But bear in mind the R65 piston diameter at 82mm is the same as an R75.

I doubt if there is any great increase in power because to achieve that you need to get more mixture in as well as burning it efficiently and an ignition system can't do that on it's own.  Dual plugging does enable the use of  less ignition advance which is a small improvement in efficiency and it's usual to tune the carbs a little weaker which should improve mileage.  

[montmil]

Barry raises interesting considerations regarding twin-plugging. Ignition advance/retard, improved efficiency and improved mileage are all correct. However, these good points regarding dual-plugged street machines may not be of interest to someone planning a blast across the Bonneville Salt Flats where top speed trumps all else.

And don't forget about the BUB Bonneville races. You can buy in -you and your bike pass tech inspection- and you'll get two timed passes down the Salt. Run whatever you brung as their are no class distinctions for this special no class class. You get to keep the timing slips plus the tech sticker pasted on your motorcycle earns bragging rights at the local Bike Night gatherings.

http://www.speedtrialsbybub.com/2011_event/index-2011.html

[MR.E]

Cheers fellas, with some reading I've done and your advice here, I think I'll leave it off the list for now, I'm not increasing the bore just trying to push the standard 650 lump!!

Thanks for the info monte, though me been me if I'm in I'm winning!!
The 650 push rod record is (while I've not started tuning and am optimistic) achievable!

Lucky enough the pending beaches are been opened soon for LSRattempts