Hello Dave
I too will be fitting a 914 if i can get a FWF.
I have no experience working on Rotax, but have experience on BMW R100GS that
uses
the same carbs.
Here is some things I would look for:
Go up and fly around with the engine misfiring in the bad zone for a few
minutes,
then shut it down and land.
Pull the plugs, you should see all the same color, light tan. If you see white,
that is too lean or plug too hot of a heat range. Black, too rich, too cold a
heat range or oil fouled.
Make sure you have the proper heat range plugs and that all the plugs were
tight.
loose plugs cause no good to happen. make sure no cracks in insulator or at
the tip and proper gap, and no carbon pieces between the gap.
Make sure that your carbs are operating that the cable and nipples are not
binding
at all. If one were to bind, you can have perfect sinked carbs at full throttle
and at low throttle, but if there was a bind/they could get out of sink
at that point between the 2 points. In other words 1 cable would effectively be
shortening up..
Look for any and all leaks in any and all hoses associated with carbs.
Change your plugs.
"CARB SNOT" Those carbs are susceptible to having things get plugged up,
especial
the enriching circuit. Is your motor harder to start now than when it ran well?
pull the carbs, clean out all the passages, pay especial attention to the
passages in the float bowl, that is what most often clogs on me. On my cycle,
could usual get away once just cleaning the float bowl, and do the whole carb
the second time round. Make sure you have new float bowl gaskets.
Check the float height, if you were too rich check to see the needle valves are
not leaking.
Go out and fly, still a miss? Try chocking the motor and see if it helps. The
Bing
has only an enriching jet, not a traditional choke, but if you see it helps
you are on to something. The jet needle has a few positions. See what stock
setting is, moving the clip up (Higher on the jet needle) will cause the jet
needle
to go further down in the needle jet, this will cause a slight leaner mixture.
Moving it down will cause a richer mixture. i would be a lot more willing
for you to go 1 click richer than leaner.
If still missing, you could go up and fly around, get it in the miss range and
turn off your fuel selector. When it begins to run out of gas that will be
causing
a lean mixture. Do not do this for very long at a high power setting. If
you feel it is running better, then a rich mixture could be the culprit.
Are your air cleaners clean? You did check the turbo and all associated rubber
and connections, looking for cracks and scuffing in the hoses.
Can you run the motor an the ground with the cowl off to see if at the problem
range has the carbs shaking a lot? Maybe they have a harmonic shaking them?
didn't
you just change the flanges?
Check any hose that may have gotten hurt going to the carb again, when you were
fooling with the flanges.
Are you running lean because you are starving for fuel to the carbs? are your
filters
clogged? What happens if you flip on the second fuel pump?
Check on the ground that you have enough return flow. Note on my accelerated
cockpit
module, the outlets on the tank were at least half blocked because who ever
assembled pushed the screen in too far. Also the nipples used all around had
a very small bore, for certain restricting. There was 1 nipple in the whole
thing that had a nice diameter bore made by another mfg. I made all my IDs the
same by boring out on my lathe. I doubt it would not allow enough fuel to allow
the motor to run, but may very possible restrict with both pumps on trying
to keep fuel cool, like at high altitudes.
It may be running hot because of the summer? Vapor lock? think second pump on
may
help?
Is the pressure to the carbs within tolerance in the miss range? Can you monitor
fuel pressure at the carbs versus the airbox pressure?
Did you check the connections and ground to your ignition boxes? Are they
getting
exceptional warm?
Good luck
Ron Parigoris
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