Engine managment

[Wayne]

OK the tiny tachs are mounted together under the main frame attached to a peice of 6061, the wire is wrapped around the spark lead near the spark plug 4 times, the earth wire is between the pull start and the nancelle mounting plate and bolted to the holding the main plate on the nancelle under the washer at the bottom inner side near the pull start hanble, so about 5 inches from the spark lead.
At this point I should state that one works fine and the other is ok up to full rpm then goes off up to 9900.

[Wayne]

And a side veiw of the wire between the nancelle and the pull starter. you can see the red wire leading to the spark wire and the black earth going to a nancelle bolt.

[Wayne]

And a quick peek at where I am upto with series 111.

[gdewsbury]

Wayne
You may have a bad ground, loose connection or a lead broken inside of the insulation. I would start by switching the tini tach pic up leads across engines to see if the condition follows the tach or engine. I experienced this when an ignition lead had broken inside insulation causing spurious signals that the tach interpreted as more sparks. It is normal for the C2 model of tach to stop reading at 10,000 rpm as this is the top of its range. Knowing if the problem is with the tach or engine will at least give a starting point for finding the problem.
Glen

[Shannon]

I have taken the Lazair series 3 out of the hanger and run the Rotax motors for a short time from idle to full rpm at short intervals.
the motor that always ran well is still doing just that at 5510 rpm with no flat spots up or down.
The other is running at 5220 with no flat spots, but the tiny tach then goes to 6600 rpm 7500 rpm then upto 9900 rpm ?
I am guessing that there is a fault in the tiny tach or a broken spark lead ? anyone know what is happening here ? any help is appreciated.

Wayne the engine running 5220 is not running right (or you are getting a faulty tach reading). Personally I wouldn't fly it as you will have one sick performing plane. The engine probably just needs some adjustments either carb or ignition (most likely carb). Under normal circumstances you should be seeing 5700-5800+ on new engines. There is no long break-in period either as the engines will develop proper revs right away.

Also did you put some fresh lube grease on the crank wipers that lubricate the ignition point rocker arm to crankshaft contacts ? The grease that was originally factory applied is probably (surely) hard, cracked and totally dried out by now.

[JPXman]

shannon what kind of lube do you use on the back end of the crank to lube the points?

[Shannon]

My old manual only states "water repellent grease" with no further specifications. A quality grease such as Valvoline Durablend Synthetic fits the description. What do you advise ?

DuraBlend® Synthetic Blend Grease

Formulated to provide excellent high and low temperature protection
Provides excellent high- and low-temperature protection (-25°F to 400°F) over conventional greases
Exceptional resistance to heavy loads
Moly-Fortified for increased film strength
Excellent water repellent
Inhibits rust and oxidation

[JPXman]

i used white grease but synthetic sounds better in this application. i wipe the end of the crank with a degreaser first.

[Shannon]

I'm thinking exact grease type is not a super-critical thing. Having little, old, or no grease on the crank-wiper however would be critical. I recall one case where someone had apparently forgotten this step on engine rebuild. All the original grease had been cleaned away with solvent and the new points were subsequently run "dry". The "phenolic-plastic" block on the points rocker-arm had worn considerably throwing the ignition timing completely off. Additionally I've seen some old low-time engines with grease that had turned dry and chalky from age-storage-heat. If memory serves me correct one set of points were stuck open from the old hardened grease. Anyway just yet another thing to be aware of.

[Wayne]

Gidday Shannon,
You are correct in that one engine the points were stuck, i used a light machine oil and a wiggle of the points they freed immediatley. I had a 1967 Holden premier with a larger version of the same points, so I know what you talking about here.

I will test the Lazair tommorrow, first by changing the tach over to the other side if that doesn't work then change the spark plugs, then if that dosn't work the motor comes off and I start to play with points,ignition, leads.
Any tips about getting the grease on the points without pulling the motor off ? I hate those stud nuts.

I have just retourqued the heads and was surprised how much the nuts turned so I think a little air suck could have been going on as well, I have new sets of seals coming so I will address each issue as it arises.

Anyway a preveiw of the lazair is all I can offer, I should do some taxi work tommorrow, I'll post a movie if this site uploads it.