How tight is tight?

Heat it with your heat gun and then try to start it. Sounds awful tight, though.

Rein

Hi Dave,

Yes, new ABC engines can be tight. However, they should not be so tight as to not be able to hand start.

Right out of the box, make sure the piston is well oiled. Flood the glo plug hole with fuel and let the engine sit for a while. Turn the prop over by hand many times. Replace the glo plug and turn it over some more.

Using a chicken stick or 90 size starter, attempt to hand start the engine at about 1 turn rich from the manufacturer's recommended "starting point" for the main needle. Starting a tight ABC engine that's too lean or dry can destroy it in 10 seconds. The first 30 seconds are probably the most critical to a good break in.

/Having said the above, tight ABC engines are not only unnecessary, but I consider it poor quality. I bet 90% of the excess tightness wears in within the first 10 minutes of running. It takes a lot longer for the next 5% to wear in, etc. In other words, the tighter the engine, the faster it wears to the correct interference fit. Once the proper interference fit is achieved, wear is infinitesimally slow. Why give us poor end users a fit by making us machine the final .0005" off the piston/liner fit? Do it at the factory for Christssake! Oy...this subject is going cause me to catch a hernia some day. /

Good luck,

Bob

On 7/22/2003 1:46 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

Have you considered removing the glo plug, putting some after run oil in the cylinder and turning the engine over with the electric starter with the glo plug out ? I did this on a very tight 46 I had. Used the starter for about 30 seconds, add oil, use the starter about 30 seconds, add oil. Did this for about 5 minutes.

Dave, if you can't turn the engine over with the prop, the prop nut is not tight enough. If you really can't turn it over with the prop, the engine needs sending back.

Bob

Heat the cylinder with a propane torch and do NOT run this engine cold to break it in. While I don't have the engine you speak of, I've broken in several engines that were at tight as you describe. A little rich is desirable but not so rich it is running cold. Using a torch to heat the cylinder to about 200deg F. will help get it started and protect the rod on that first start. If you can get it running for 15 min you will love the engine. I look for engines that are as tight as you describe.... even if they are a pain in the ass the first start.

Bill Vail

That seems very tight indeed. Take out the plug, Use pure oil, without methanol, heat up the engine to quite hot, and use the starter in short bursts to turn the well oiled engine over, until ready to accept hand flipping. Be generous with oil applications between external powered runs. Slowly let the engine cool, but keep turning it over using short bursts with the starter. Methanol will dilute the oil too much, which in turn will pinch the piston, and prevent you from starting the engine. Once loose, the engine will perform better than a non-pinching one.

Good luck with it.

I purchased an OS .60 FP a couple years ago. For about the first 50 flights the engine was very tight. The only electric starter that would turn it over was one with gear reduction in combination with a freshly charged 12v battery. Hand flipping it was impossible.

Now the engine has loosened up and it starts easily with a simple flip of the prop.

However you engine does sound too tight.

I doubt a different piston and liner would be any better...

If you haven't realized it by now, what you have is a highly desirable quality in an engine. The tighter the engine is when new, the better the piston/sleeve seal will be when it's broken in, and the more power it will produce.

Get yourself a decent heat source, like a propane torch or a REAL heat gun (1500F, not a hobby heat gun @375F), heat up the cylinder, and begin the long breakin process. This one ain't gonna be flyable in one tankful like an OS.

Take a hatefully tight new engine, and a precision fit engine. Run a gallon of fuel through each. I guarantee the tightness will end up identical, or so close it's almost imperceptible. All other things being equal, both engines will last about the same number of hours. Objectionably tight engines are just that. Objectionable. Do not misread me. Tight is alright. Excessively tight (Where hand starting or using the appropriate electric starter is a PITA) is shoddy quality.

Bob

That sounds a _lot_ more trouble than just loosening the glow plug a half turn and using an electric starter.

Agreed. I would send it back if it was that tight. It will have to remove a lot of metal to get the correct running clearance.