engine Seizure

tallus

Hi guys .. anyone ever seize an engine while running it in ? I just did on 5% fuel .
Didn't overdo it at all, just wondering if anyone else here has had the same problem and if so how did they get around it/prevent it happening again.
T

coolwings

If you are on 5% that will be a soft seize. No problem.
It happens when the engine stops while hottish.
It stops hot, and no cooling is present after it stops.
the fuel for the next engine firing is sitting on top of the piston and it bakes/fries in a little brown ring of varnish around the piston edge.
You'll see it on the liner in the position of piston top, just below top dead centre.
(On 5%) The metal is not seized at all.

just take off the cylinder head, and use a cloth or dremel type felt polisher and some acetone, nail varnish remover, or white spirit. Don't use abrasives or a slight loss of power occurs, spirit is enough.
When the brown ring is gone, lube slightly with a drop or two of fuel, and put the head back on, then finish running in.

If an engine stops during running-in, and while it is hot, (ie after a fast revving period), assume that it's hot enough to do this again. And just walk to the car, and prime the engine, then pull starter cord once to bring in the extra cooling fuel, and it'll never happen to you again.

BTW , set it a little richer until it's a bit more run in than it is now. You probably just leaned it out a little soon, that's why it cut out in the first place, (assuming it didn't run out on empty tank).

You "might" need a new glowplug to finish running in, it will have got hot too and used a bit of it's life up. They generally don't last the running-in period, so the one in it may perform a bit tired when you get going again.

Cheers

Coolwings

tallus

Thanks for the advice coolwings, and I think you're right about not having it rich enough. I did rev it a little bit but not much and after that it seized. I have since unseized it by removing the heatsink and cleaning around the piston with fuel, thankully it was a soft seize ;-) I will also change the plug as you advised.
cheers :-)

coolwings

tallus wrote:

...I have since unseized it by removing the heatsink and cleaning around the piston with fuel, thankully it was a soft seize ;-) ...

It's the big reason for running in with straight or maximum 5% fuel.

With high compression engines all it takes is a 30 second delay in pushing in that bit of fresh fuel after a hot cutout and you have it seizing (while stopped) and while you walk to it.

But with low nitro you only have a little brown varnish circle to clean off....

tallus

how much fuel should I use to run it in ? I got a litre of 5% with it.

coolwings

Depends ... I judge by watching the settings change, when they stop changing I call it run in.
Good "hard metal" engines about 10-12 tanks.
Basic engines maybe 6-8 tanks.
Just my personal view.

There is a lot of running-engines-in info on my own webpages here ....
http://uk.geocities.com/norm_flyer/index.htm
click on the running in menu link.

tallus

thanks ;-)
Excellent Link :-0