I have a brand new Tower Pro .46 that has a very tight fit between the piston and cylinder. I put some after-run oil in it to make sure it was well lubed. With a prop installed it can be turned, and I am sure that my electric starter will turn it over when I start the break-in procedure.

Am I correct in assuming (dangerous, I know) that it will loosen up quickly after the initial ignition, when the cylinder and piston start to mate?

Should I put in a lot of after-run oil and remove the plug and turn it over with the starter to help "machine" it a bit to loosen it up before trying to start it?

That is perfectly normal. As the engine heats up the fit will loosen.

Okay, if you say so![8D]

This is my first non-OS/YS engine and I have never seen one so tight the piston and cylinder were scrubbing against each other like these do.

I'll give it a go and let you know how it comes out. A lot of guys seem to like these engines.

Be assured the tighter that fit the better your engine is going to be. Never turn an engine over by hand dry In fact don,t turn them over by hand at all when new. Always back up the engine aginst compression before using the starter and use a good quality spinner nut/silicon insert interface. Always use two hands on the starter and a helper to aid in holding the airplane if restraints are not used. Always be carefull to assure that the axis of the starter shaft is in alignment with the engines crankshaft.

John

Thanks much. I have run and tuned many 2- and 4-strokes, just none so initially tight as this one. I guess it'll be totally fine once it runs a couple of minutes.

It's my first "budget" engine, which I put on a little Dave Patrick Ultimate... so I wanted to make sure I wasn't making some stupid mistake that could damage the con rod or piston/clyinder wall.

On a new ABC engine, I heat the cylinder (propane torch) when I'm ready to run it the first time. This provides some piston/cylinder clearance.

After the first run, it is usually OK. Do not run the engine rich.

Paul

All of my Tower engines (1-.46, 2-.75) have been extremely tight when new. I had to use a heat gun on the cylinder to be able to start them the first time. After that, they hand started easily.

Use caution with a powerful starter when starting the engine the first time, especially in cold weather. You can break the crank pin off or break the connecting rod.

Ok, the heat gun is a good idea... I can do that here at home on the deck, where there is an electrial outlet available.

This is a new experience for me. But as long as the engine runs fine after this little hassle at the outset, no problem.

Hey, guys, I just want to say thanks for the advice. I was able to get out and fly today, and after a little break-in run alternating rich-lean-rich-lean for one tank, and then another 1/2 tank to tune, it was ready to fly. Cool Power 15% nitro. Needle open 1-3/4 turns was slightly rich.

The idle adjustment out of the box was way too rich, so it took a few tries to sneak up on that setting, but after that the transition was excellent with no sagging or stumbling even after extensive idling, and the idle was excellent and solid, so much so that after a couple of flights I felt comfortable doing some spins and blenders, with nary a deadstick with any of the 4 or 5 flights.

I am very impressed with this engine! A friend of mine who has run only OS and Saito was really impressed as well.[sm=thumbup.gif][sm=thumbup.gif]