George Ryals wrote:I seems to me that worrying about top end timing retard on a street bike (even with dual plugs) is unnecessary. Now, if you spend a lot of time at WOT with dual plugs it may be worth while to look into it. Of course the only way to really know is a lot of time on a dyno that can load the engine at steady rpm...8500 or so while you find the sweet spot.
From what I have read, dual plugs have the most efect at lower RPMs as the flame front starts at 2 points makeing combustion happen faster. As revs increase and things happen faster and less advantage is gained to the point that in the range of our redline dual plugs have little to no advantage over a good single plug ignition.
The advance curve is critical though, it must rise more steeply at low rpms and then stop about 5 deg sooner but at about 4000 RPMs. Again this is what I have read but I have no first hand experience.
Best way to achieve "fuel economy" on any given motorcycle
will be to wear a wrist brace on your right hand.
Sorry, that's as good as it gets, and who wants to do that ?
Beyond that, if fuel economy is a serious concern, I'll beg the question – why are you f#cking around with an antique BMW ?
There will be many better (2-wheel & 4-wheel) options to provide economical transportation.
"Here am I floatin' 'round my tin can far above the world
Planet Earth is blue and there's nothing I can do"
I think that the general efficiency of dual plugging does enable you to lean out the mixture a bit, some BMWs were jetted fairly fat to help dampen down pinging.
My 1070 bike uses 10-15% less fuel than my mates R100R, at fairly modest touring speeds.
The other efficiency gain is from reliably running a higher compression ratio without pinging. Smoothness and easier starting are a plus!
On the timing side, yes you do need to reset the timing to around 28-29 degrees at full advance, remember that full advance on a Boyer is around 4500 rpm, so the retard is applicable over a wider range of revs. Jim Cray reckons that the ignition curve on the Boyer twin plug microdigital is not optimum and fits his bikes with the basic Boyer ignition, setting the ignition on full advance and letting the static ignition timing fall where it may. Boyer ignition curves are fixed, some of the German ignitions have up to 16 different curves to play with.
if using bings the biggest fuel efficiency improvement for your money is found by replacing the needle jets as over 25000 miles or so They get enlarged by the mechanical vibration of the needle.
Charles
Charles
Replica 1070 R90/S (based on 82 RT)
1975 R90/6
vanzen@rockerboxer.com wrote:Dual plugging for fuel economy ?
Best way to achieve "fuel economy" on any given motorcycle
will be to wear a wrist brace on your right hand.
Sorry, that's as good as it gets, and who wants to do that ?
Beyond that, if fuel economy is a serious concern, I'll beg the question – why are you f#cking around with an antique BMW ?
There will be many better (2-wheel & 4-wheel) options to provide economical transportation.
"Here am I floatin' 'round my tin can far above the world
Planet Earth is blue and there's nothing I can do"
... except, perhaps, enjoy the ride.
You are allways some damm practicle.
My car (actually my wife's) gets better gas milage on the highway and is about as fast as my R75, but it's a frikkin appliance. If I wanted to ride a dish washer I'd get a K75 or an F650 or some other Jap bike. (no offenece to K75 or F bike owners.)
On the classic side my 1957 R26 gets spectacular gas milage, but that is because there is less tan 20 HP on tap.
chasbmw wrote:
On the timing side, yes you do need to reset the timing to around 28-29 degrees at full advance, remember that full advance on a Boyer is around 4500 rpm, so the retard is applicable over a wider range of revs. Jim Cray reckons that the ignition curve on the Boyer twin plug microdigital is not optimum and fits his bikes with the basic Boyer ignition, setting the ignition on full advance and letting the static ignition timing fall where it may. Boyer ignition curves are fixed, some of the German ignitions have up to 16 different curves to play with.
if using bings the biggest fuel efficiency improvement for your money is found by replacing the needle jets as over 25000 miles or so They get enlarged by the mechanical vibration of the needle.
Charles
I already have a couple of single plug Boyer microdigitals . Do you know what coils Mr Cray uses with them and if they are in series or parallel?
I am already running smaller needle jets as the carbs are early 70s and they where a bit fat at base settings.
I am currently using dyna browns in series on my R90/6, with the basic boyer,I sourced the coils from Jim some years ago with the original twin plug of my 1070. I then fitted a silent hektik ignition to that bike with the silent hektik coils, mainly because I got a bit anal about timing and curves and the silent hektik gave me a number of choices.
However with the R90/6 I am happy with going forward with a more basic ignition.
Charles
Charles
Replica 1070 R90/S (based on 82 RT)
1975 R90/6
"So now it's gone, spares aren't available and theres no one to talk to about it. Great...! I've been reading about teething problems with The motorad Electric system over in ADV Rider, so is the Boyer the only viable and affordable alternative?
You know, I've been thinking about dual plugging my bike and if I do, as much as I'd hate doing it, I might go back to points.
I hate points."
The bean can doesn't apply to my bike so I have not looked into it.
. Do you know what coils Mr Cray uses with them and if they are in series or parallel?