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RE: Whatcha got there??
- Subject: RE: Whatcha got there??
- From: "John Dancoe" <jdan@xxxxxxxx>
- Date: Tue, 30 Aug 2005 10:08:38 -0400
Clive cliddell@xxxxxxxxxx <mailto:cliddell@xxxxxxxxxx> wrote:
>> Cees wrote:
>> >could be a couple of Bings doing the work down there
>> They ARE Bings.
>> Mine aren't...anymore...
>Whatcha got there??
Hah! Someone finally took the bait.
"Long-time list members" (who know my capability for extreme verbosity), will
appreciate this "succinct" report.
"Long-time list members" know that:
(1) I have a long history of animosity toward Bing carbs
(2) I've always been disgusted with how reluctant my '93 R1100RS was to
(3) I've been threatening to replace my throttle bodies ever since I
discovered they were Bings ("no wonder they go out of adjustment every few
(4) My bike was running progressively worse for the past 3 years
(5) Early this year I conclusively determined worn throttle bodies to be the
(6) About the same time, Tom Cutter reported "go-fast boys in Europe getting
108 HP" from R1100Ss "with 41mm smooth-bore Mikunis"
Replacing the throttle shaft in the RH throttle body helped with (4), but
since the shaft bore was visibly damaged it was no surprise that the repair
did not come close to restoring my bike's original performance. I concluded
that replacement of both throttle body assemblies was required.
One possibility: buy a new set of Bing throttle bodies.
In light of (1), (2), (3), and (6), I rejected that option.
[There's a long and I think pretty cool story here; skipped for now.]
I installed a set of 44mm Lectron "Power Jet" flat-slide carbs instead.
My goals for measuring a successful conversion were relatively modest:
A. The bike MUST start
B. The bike MUST idle
C. Performance MUST be comparable or superior to new
D. Fuel economy SHOULD be comparable or superior to new (not actually
I now have 1,868 miles on the conversion.
Note that I do not consider the tuning complete. In fact, the throttle
twistgrip/cable assembly that I concocted needs another revision, because I
can't actually achieve WFO with the current assembly.
But I am happy to report:
A. The bike starts BEAUTIFULLY. I could not ask for better starting. It really
is exactly what I was hoping for, an order of magnitude better than it EVER
did before, and I am absolutely thrilled with this.
B. The bike idles reasonably well, although not quite as smoothly as the F.I.
did when it was running right. In general, with carbs the engine seems to have
a bit more "attitude" (which could be a euphemism for "roughness") than it did
C. Performance is indeed comparable. I don't know if it's as good as new (I
never dyno'd it so I'll never really know), but seat-of-the-pants says my old
friend, who was deathly ill for years, is BACK! I was able to hit 0-60 in
approx 4.3sec vs. the original spec (IIRC) of 3.4sec. Note: that's a bike with
75k miles on it, 7/8 throttle available at best, and me, eyeballing a
wristwatch duct-taped to the triple clamp; NOT a professional test rider on a
new, professionally-tuned, blueprinted bike, with radar timing and
instructions to "turn in the best possible time, even if you blow it up in the
The bike certainly has more power than clutch, I could smell that after the
first run. Top end is frankly poor, but I have not yet even attempted to tune
in that range (I don't spend much time there), and as noted above, I can't get
WFO with the current cables/twistgrip anyway so what do you expect.
D. Fuel economy is comparable. On a couple restrained freeway rides, I've hit
42 mpg, which is actually as good as I ever actually recorded with F.I.
(though I think I've done better on occasion). In day-to-day riding, I have to
admit economy has suffered about 8% (165 miles to low fuel warning, vs 180).
However, my last plug checks indicate it is still running rich.
Also, I suspect 44mm is probably bigger than a carb should be for this motor;
I'm sure I'm losing intake velocity and economy that I'd have with a smaller
bore (like say 41mm). But 44mm was the closest match that Lectron had
considering overall geometry.
IN CONCLUSION: COLOR ME HAPPY.
If you would like to hear the whole, sordid story (which I warn you is 30
years in the making), let me know and I'll finish writing it and send it to
If the LIST would like the looooooooong story, have a vote; I think it would
actually be in the very best spirit of why this list exists in the first
place. But I won't expend the bandwidth without a few nods.
John Dancoe AKA "Manfred von Blitz" '93 R1100RSxABSxFI AKA "Nada 3"
p.s. I'm not selling kits at this time, and until I have a lot more miles on
this project I would not recommend anyone following my lead. But I am
considering making kits available and if you are interested, let me know. As
far as I know, I'm the only person in the USA to have done a carb conversion
on an Oilhead, and probably the only person in the world to have done it with
Lectrons. Also note: I think that Dell'Ortos or Mikunis would probably be
excellent choices. I close Lectron based on favorable past experience on dirt
bikes, and the likelihood that proper jetting would be much more
time-consuming to accomplish with other makes.