ZS-DUT

[jantar]

I am pleased to inform members that on Friday 10 Dec 2010 Nipper ZS-DUT was restated for the first time in 10 years. It started easily on its mixed dual electronic ignitions and ran very sweet. I have to set Compufire timing next start, but it must be quite close at present. Oil press steady at 3 bar. oil temp. not reading (sensor?) and alternator appears not to be charging ( this is a puzzle for me). Electronic rev counter seems to be reading X 2 so I am resetting for 8 cylinder as I suspect Leburgs waste spark is misleading it. My pushrod tubes are not the stock VW (corrugated) ones but seem to be telescopic pattern. does anyone know these and their seals? More news and some pics soon. Thanks to all for the help over the past year. Jantar

[JAB]

Congrats on your achievement, another grinning face.

I use http://www.vwheritage.co for all my gaskets etc, they are reasonably priced and quick on their delivery.

Best of luck for 2011

JAB

[jantar]

Thanks for reference to vwheritage. From their on line cat. I identified my pushrod tubes ! This is a huge help as I find these to be superior to originals and can extract same without removing heads ( thats for later) Now on 4th & 5th starts have got all the engine systems working. First the electronic rev counter it now reads more credible numbers and has been reset as a 2cyl motor!--- probably a Chinese mistranslation. Oil press is 3bar normal and 2bar at hot idle so this looks OK. Oil temp. now registering but reading low--I will recalibrate or maybe find the right resistor to put in parallel. The alternator, well I did a check of stator coils and transistors in rect. but have no check for the reg. zenner diode. Started up and this time it worked!!! I suspect a faulty connector. Now I get 15V when running Leburgh alone and 13V when running Leb. & Compufire. Compufire ignition is quite greedy on current and you can watch the volts go down on an unassisted 7AH battery. It takes 4.2 amps so the alternator is essential. Leburgh draw is minimal.
Having had a battle to fit rear spinner plate (you must reverse it to clear Leberg timing disc) prop and spinner (also to remake) I now discover that the prop is much too close to lower cowling lip with prop vertical and have embarked on a "refit the cowlings mission" Suspect that lower cowling was never a good fit, but already its looking better. Things seem to improve each day---long may it last. Jantar

[Neil Spooner]

Well done!!
Seeing the engine running on the a/c is fantastic, and once you have the carb' adjusted and it's ticking over nicely it's just great to sit and watch
The Leburg ign' is a waisted spark system, so you get two sparks per four strokes, or to put it another way, one spark per two strokes!! Hence the revcounter setting. If you can find an optical rev' counter that is the best way to set up the revcounter, failing that a timing light with a revcounter. Some multimeters will offer a frequency counting facility.
Oil pressure sounds fine, 10psi per 1000rpm is ok hot.
Where is your oil temp' sensor? If it is mounted directly in the engine case on the sump it will tend to read low, as the magnesium case works well as a heat sink. I moved mine from the engine case to a "manifold" in the oil pump inlet line, initially got a shock as the oil temp' indication was up 10degC, but this is a more accurate indication. It is also just before the oil pump, so is before the oil filter and cooler. The oil cooler gives about a 5degC drop across it.
Regarding your cowlings.....can you move top and bottom cowling back by redrilling the position of the dzus fastener holes? Or maybe just the lower ones? Try fitting top and bottom cowls, fit the top clips to fit the top cowling to the fuselage, leave out the lower ones, and see if the whole lot will tip downwards?
Make sure your baffle fit is excellent, and you have a good seal around the edge, once you load the engine up in flight any leaks will tell in high CHT and oil temp'.
Good luck!!!

NeilS

[NeilD]

There is an output on the Leburg system to run a normal rotax rev counter - the manual says which one to use, but if i recall, it is one for a 2 cyl 2 stroke.

[jantar]

Thanks Neil S and Neil D . I am already refitting the lower cowling. My attachment points are 10mm alloy tube posts (4 no.) on lower and (2no.) on upper, so I file out repositioned holes in glassfibre for the posts, change the length of the posts as necessary and make good with alclad discs (to take the wear of the saftey pins) and glass epoxy. There are 4 Dzus each side of upper/lower join.Work part done and now have 6mm clearance at bottom of mouth. OK ! Lots of mods to upper cowl to accept Compufire dist. and Ford long tower coil pack. Have been very serious with baffles closed all redundant holes and gaps. When cowls finished want to run for about 20 min at 1500 + to observe gauges etc. Wing is not mounted and fuse is anchored to a golf cart for run up. Still some airframe work pending ,then inspection, but its Xmas and in SA they combine with summer hols and NOTHING and NOONE works------ah well. Will send some photos when work permits. Not many visitors but had a snake last week-----rather dangerous ! Any guidance for positioning rockers along shaft to centre over valve ends? Have been moving shims around but need some with negative thickness. Jantar

[Neil Spooner]

A couple of thoughts.......
If you run your engine up to full power without the wing/weight in the fuselage the prop' torque can roll the a/c onto its side......one shock loaded engine and a trashed prop' results, beware of the flying bits of wood!! (didn't roll mine, but got one u/c leg off of the ground for a moment with me in it)
Originally the tappets were offset to one side of the valve tip to rotate it, so it is normal to find the tip of the adjuster doesn't center on the valve tip. There are various ways of reducing valve tip wear: Elephant foot adjusters; Swivel foot adjusters; and Lash caps. I personally use lash caps, I had an Elephant foot adjuster fail, and the Swivel foots tend to wear the valve tip. So lash caps are the simplest and most reliable. If you have a slight amount of offset of the adjuster it doesn't matter. Use standard length springs, at the rpm we use we don't need the extra spring pressure, it increases valve train wear, increases oil temp' and wastes power.
............snake in the cockpit !! didn't they make a film about that!!
Neil

[jantar]

Thankfully not in cockpit ! Re torque thats a very important point and will save me from heartbreak, so I have been warned. Jantar