Microlighters

Had to do an annual inspection, on 400 hour rotax silver top, on clipper bought and half delivered to GHT a while ago, for change of ownership.

Well respected AP opened motor, replaced rings, honed cylinders. Crank etc all still ok, and all rest within allowed tolerances.

Re-assembled motor, started and run briefly, AP went home.

Yesterday, started run -in procedure. Motor gets hot, after 3 minutes of idle. Water temp to about 100 - shut down.
Did many checks during the day. Replaced with better coolant. Checked radiator cap - still holding pressure. Heads off, gaskest etc ok. Barrels off, cylindres off, gasket at bottom ok. Ring gap was meassured by ap when installed. Ok. Checked water pump. Radiator getting hot at gradually, correctly, until very hot. Tried without thermostat.

Tried everthing the ap and others could think of. Always the same - about 3 minutes, temp builds to 100 odd, switch off.

Ap now sending another silver top head to change heads, says it might make a difference.

Why are we forced to open perfectly good motors???? Fun, hey.

Ideas??????

LM

Hi Larry,

The title says it all and should be a pointer for the future.

Kind regards,

Gunter Rostek.

Agreed

Skidmark makes non-invasive crank testers. This is about as far as we should go at inspections. See here

viewtopic.php?f=1&t=7005

Agree, engine like a 2liter of Coke, once opened they allways go flat no matter what you try,

Possibly airlock in water system. Waterpump cavitating, not circulating the water.
(my uninformed guess)
Methinks buggerall to do with heads.......

There probably is nothing wrong with the engine. I think you are ground running it for FAR too long. Once it starts overheating, it will not cool down, because the cooling system has not been configured for extended ground running. So fire it up, taxi to the active, and as soon as the temp is on the numbers, FLY. Give it some cooling air. If it still overheats, it is trying to tell you something. Mmmmmm. Maybe some "finger trouble" here.

Thanks, guys. Boet, will try that, but generally you should be able to idle for a while, plus I was told to do the full usual hour plus run inns.

Also thought of water not circulating, and emptied the system again, trying to make sure. Opened pump, checked impellor. Radiator gets hot evenly, from the back forwards. No kinks in pipes. With radiator cap off, no bubbles os sign of trouble, water seems to be circulating.

Will try another head today, and if that doesnt work, going to put my old rings back in!!!

LM

Hi Larry,

Have a look here for ideas

http://www.ultraflightradio.com/bytopic/engine.html

Kind regards,

Gunter Rostek.

You mentioned the ring gap was measured after installing the new rings. Was it measured ON the piston or was it inserted into the sleeve by itself and then measured? I've seen someone once before put oversize rings onto a standard size piston and crammed it back into the sleeve

Next thing to check, silly as it may seem is the heat gauge and sender itself. I've had one go south on me before for no apparent reason. Must be a matched set. Gauge and sender, that is. I did some work on the motor and afterwards noticed my temps were very low. Got the right readings back once I changed the gauge and sender unit. There was nothing wrong with it before I started work on the motor. Go figure. Could be that you don't really have high temps, only the gauge smuggling with your head...........

Thanks for suggestions.

Rings were checked in the cylinders, should be no problem. If left running, engine will boil, so defintely not only the gauge.

Ok, took the head off, replaced with another. Same thing. Drained water, checked for airlock, nothing. Pulled heads, barrels, etc again. Put old rings in, closed whole thing again. Still getting hot.

Took Boets advice. Let it cool to about 80, taxied out, high speed down the runway, dropped a little. Got the little light behind me, opposite direction, took off, immediately dropped to about 60!

Phoned one of the agents , immediately asked me if I ran a hosepipe over the radiator??? Apparently the manual says to run a hosepipe over the horizontal radiator. Never got a manual with the old trike.

So anyway, looks like problem is solved, with lots of uneccessary work.

Moral - RTFM, or phone your buddies.

Lesson for all Air Creation owners / flyers / agents!

Cheers

L