*Crash*Johnson*

My Feedback: (7)

All,
Before you start with "DO A SEARCH ON THIS...." I did. What I came up with was 50 posts with: "DO A SEARCH ON THIS"
I also came up with "Read the instructions". If any of you have a TT .61 please read the instructions, and tell me where it reads about proper break in. It doesn't say anything...

My question: How did you break it in? a couple of 30 second bursts then minute burts then 3 minute ect?
One tank idle. One tank with 10sec burts ect?

I dont want this to be a flaming war about "My way is better than yours..." please.

William Robison

My Feedback: (3)

Greg:

Just put a low pitch prop on it, and let it scream on the stand. ABC/ABN engines need to run hot and fast for breakin with relatively low load. Stay on the rich end of peak rpm, and get three or four five minute runs on it about 9,000 to 10,000 RPM. Then go fly.

This might still be a little soon for a good idle, but it will idle and it'll get better as it runs.

Bill.

downunder

It's instructive to read something like the Jett engines page on running in. For one thing it's probably the closest I've seen to giving an idea about initial needle settings. What they say is completely the opposite to what's considered to be normal for an ABC but you gotta admit they seem to know how to make a somewhat decent engine
http://www.jettengineering.com/tech/breakin.html

The Rossi instructions need some interpretation (I'm sure it was written by some local kid who'd done a 2 week correspondence course in English) but it appears to be very close to what Jett say.

DarZeelon

"Crash", William,

I would have to disagree with you, William, on one issue.
You wrote "Just put a low PITCH prop on it,...".

You should have written "a low LOAD prop". The ideal prop for break-in (Dub Jett...) is "one inch less DIAMETER, same pitch".

The reason is cooling. A same pitch prop with a smaller diameter would reduce the load on the engine, while maximizing the cooling effect.

During break-in, you want the tapered-bore engine running at its normal maximum RPM, while under a lesser load, with a rich, two-stroke mixture setting and with good cooling.
A prop with less pitch will lessen the load, but will also lessen the cooling, from lower speed airflow.

GRANT ED

I ran my 61TT in last week and did exactly as William suggested. Ran two tanks on the ground flat out. So far so good.

*Crash*Johnson*

My Feedback: (7)

Cool thanks for the replies guys!

As far as the stand, since it is mounted on the plane I guess that is my stand
I live in an apt and have no access to the outside world but to hop in my car and drive to the field. I'd look silly with an engine sitting on a stand there I can hear it now... "That thing wont fly!"

jaka

Hello!
William is correct!
Just run it ...a little rich using a(11x7, 11x8, 12x6 APC) at full open throttle ..adjusting the rpm with the highspeedneedle....one whole tank! Then fuel up and fly!!!

Remember this is not Rocket science.......

Regards!
Jan K
Sweden

*Crash*Johnson*

My Feedback: (7)

I was gonna use an 11x6, but I have an 11x7 and 11x8 I can use.
Rocket science no, but I spent hard earned money on it and would like to make it last a long time. From the info I gathered inproper break-in leads to quicker wear and poor performance down the road. I'd like to prevent that if at all possible.

Sport_Pilot

Jett probably makes the best 2 strokes ever. I notice that they don't go for this run the engine two minutes and let cool down nonsense. Doesn't accomplish much except to waste a lot of time. Though I guess it does help if a beginner is running the engine too lean.

NM2K

My Feedback: (14)

Is the engine ringed or non ringed? This is the most critical aspect of break-in.

If non ringed, which I suspect, then just fly it in and make sure that it is not too lean or too rich. I know, what is too lean or too rich, right? Well, better too rich than too lean, but don't over do it.

An 11x7 prop would be perfect for break-in, whether ringed or non ringed.

Keep the nitro within reason. I wouldn't exceed ten percent nitro without adding a head shim to lower the compression. Will the engine explode if you run it with more nitro and high compression? No, but it won't help it any.

If the engine is equipped with a piston ring, run it very rich for the first several tanks of fuel.

Heat cycling, whether ringed or non ringed will not hurt a thing and will probably speed up the break-in process.

Good luck.

Sport_Pilot

This won't hurt anything, but heat cycling definitely slows down the process, and doesn't do anything to help the break in. It won't make the metal stronger, you would have to ruin the engine to get the metal hot enough to anneal or harden the metal. However it does aid the nervous user in that you can check the engine temp without putting your hand near a spinning prop, and give you some practice starting the engine.

NM2K

My Feedback: (14)

I'm not a metallurgist and will be the first to admit it.

Over the years, I have had a few engines show up some defects that were heat related. Carb bodies have done strange things that bound up the rotating barrel and such. I can't say that intentional thermal cycling was the cause, since I do not subscribe to the practice either. I just don't see where it would hurt anything.

You raise a good point about short runs and cooling off periods being easier on some people's nerves.

My comment about speeding up the break-in process was not from first hand experience. I have never noticed a difference. It was from reading the OS instruction manual. I assumed that they knew more about it than myself and I paraphrased them. God help us if they do not know. <G>

Sport_Pilot

OS knows but I doubt they wrote the manual. The engineers rarely write instruction manuals, nobody seems to understand us![&o]

Jazzy

Remember folks this is a brand new engine. It IS important to let it run at normal operating temp. for the first few tanks.
If you only run it a little and try setting the idle and such all you're doing is increasing the wear of the piston and sleeve fit. You might as well mount it on your plane and set the starter to it without fuel and glow heat.
It IS possible to reduce undue wear on a new engine by breaking it in with a slightly less than normal load and at or near peak RPM with a few clicks richer than max lean setting. Letting the engine run up to temp with healthy RPMs for a few tanks WILL reduce undue wear.
I've done it this way and it DOES work. I've done it the other way, (fuel it up and go fly), and it works too but the engine doesn't seem to be all that it should be after a short time.
The TT Pro 61 can be a real screamer and performer. Removing the baffle from the muffler is a good start at gaining 1000+ RPMs - just wear ear protection.

Best of Luck,
Jeff

Ed_Moorman

My Feedback: (1)

I wish you would quit touting the methods used by Jett, or Nelson, to beginners who may not be familiar with them. A Jett is a different animal from an OS, Thunder Tiger, Magnum, etc. Most Jetts are AAC. They are essentially hand built and fitted, then checked out at the factory for meeting minimum rpm standards.

We are talking a lot cheaper stuff here with any sport engine. Nothing is the same. It's like comparing my GMC truck with a F-1 racer.

On the good side for sport ABC type engines, if you crank them up and lean them out, practically speaking you can't hurt them. As Bill said, lean it out, not max, but off a little and run 3 or 4 tanks. I like a slightly smaller prop than I fly with. You'll have to mess with the idle mixture for several tanks, but in half a gallon or so that'll settle down.