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Post script and
summary:
page created: May 19, 2000; last
edit July 4 2011
The aluminium stand-offs for fitting the engine has been replaced by a rear mount
Mousse can muffler, based on the Helmholtz resonator principle (See Goodies). in order to get a low-tone growl, instead of the metallic ring in the sound of the original ST muffler.
Now that the engine has 15 litres of fuel through, and is run in properly, the engine runs perfect at all throttle settings with instant response to throttle change, and will accept a full throttle lean setting without a flameout. It is run between 7000 and 8000 rpm with 20%
Titan oil in the fuel, some acetone (1%) and a tad of ether (1/4%). while idle is as low as 1600 rpm
The low end can be adjusted between normal and rich while still having good transition and non-4-stroking nice mid range running. When the low end is set too lean,
the engine will flame out after the long glide with touch-and-go's, but with the modifications as described, there is no need for
such a lean idle setting. Sensitivity to warm or cold engine has gone completely and fuel consumption is quite low for such a powerfull engine. Priming the engine is hardly required, and only for the first start of the day. It starts hot as well as cold.
As a piggyback workhorse, dry plane weight is 9 kilos (20 lbs) without the added
piggy back gear. To solve the yaw instability with piggyback gear fitted, span
had to be reduced to 220 cm .
I get in excess of six hauls up to full height on a 500 cc tank with engine idling in between while setting up the next glider. Take-off weight with piggy back saddle and glider is about 11 kg (24 lbs), which the engine handles with authority. These figures seem just about right for the 1-5.5
Spitfire I have on the drawing board. Gangway- here we come.
I have modified several Carbys since, and all run excellent, even without
the regulated fuel pump. Flying the throttle is an added dimension with this kind of
set-up.
Update July 2011:
Here is the drill for defining the exact amount of correction in the
translation groove that is needed.
1) set idle mixture (fuel nipple pointing to rear carb lug)
2) set high mixture
3) go to exactly half throttle
4) at half throtlle, use the IDLE fuel adjustment to get smooth running. Note
the required amount of adjustment (needle movement in mm)
5) The amount of adjustment in step 4) is the amount of the groove correction
@ idle position that is needed for PERFECT carb tune.
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