Hi all,
This last weekend I ran about 3 tanks of fuel through my os max 32sxh trying to break it in..doing this for first time on my own..not sure when i know it is broke in..is it pretty much finished when it quits spittin fuel out??..any words of wisdom out there for me?..could sure use all ther advice i can get right now..thanks....Tom

this is what someone told me in a simular post i made:

Ahhhh, this is an age old subject that has no right answer, unless the answer is yours! How long to break in an engine???

I think that for an aircraft engine, 3 tanks of fuel should be fine. That is my (very general) rule of thumb and has worked on several engines. A good indication is (after you lean it out over this process) how it accelerates. Can you go from idle to WOT without hickups? Is it smooth during the transition? How does it start? Is it making full power? If it does not seem ready after looking into these things, you might need to run another tank through. Also, a bad mixture will give bad indications such as these, so make sure it is right on!

As for a high performance NovaRossi type race engine for cars and trucks, you will need more time (like 6 tanks) to break it in due to a tighter fit of the piston and sleeve. This is what I did with mine, and now it still screams with over 1 gallon through it. It is moving my RC10 GT, so it has its work cut out for it!

Good luck!

Thank you for your time..I will probably end up running a bunch more fuel through it before it goes up anyway..haha...nobdy to hook up with (yet) to show me the ropes...at least i can listen to the motor..hahaha...thanks again

Is it spitting out fuel or oil? Chances are that it is oil. Some oil should come out of the pipe, as well as some smoke. What are you getting?

yeah..its blowin fuel out the pipe...bet its blowin more out than it is burnin..have been breaking the motor in with the needleapprox 2 turns open..

The OS 32 is an ABC type engine which requires a different type of breaking in than a ringed engine.

ABC engines need lots of heat in the cylinder to operate properly.
Except on the first few runs when the piston needs to wear into the cylinder which is "breaking in". Running it "rich" helps keep the new and tight piston / cylinder assembly cool which causes it to wear rapidly which is what "breaking in" really is, RAPID WEARING of the engines internal parts.

The engines lower end does not need any sort of running in as the precision with which engines are made these days precludes it.

With an ABC engine you need to run it up to almost max RPMs with the needle set rich so it stutters in what is known as 4 cycling.. Do this once for about 3 min then shut it down and allow it to cool completely. This creates rapid wear of the piston / cylinder assembly. Now start it again but this time lean it out (needle turned in) so it alternates between 4 cycling and and 2 cycling. Run it for 5 min like this and again let it cool completely. Do this 5 times total and your engine can be flown at almost it's maximum. These runs continue "wearing" in the piston / cylinder but at a lesser rate.

The reason you want to heat and cool the engine a few times is this allows the alloys to expand and shrink and finally seat in place.

Ringed engines are a whole different ball game. They need the same heat cycling but must be run VERY rich for the first several runs.

An example of ringed engines would be the very popular Moki line.
A Moki 2.10 requires at least a gallon of fuel to run through it at a very rich setting in order to be broken in correctly.

This is a quote taken directly from the Jett Engineering site regarding running in...
"There are more ways than one, but it is important to remember one thing: With an ABC or AAC engine you don’t really have to worry about breaking in the piston and liner as that will take care of itself.The rod and crankshaft journal pin fit is the object of the break in."

I hate to sound rude but just exactly what is your point??

Why do you leave the impression that my post was inaccurate and that engines don't need any breaking in?

If your going to quote Dub Jett, quote THE ENTIRE text not just the part that suits your agenda or your need to attempt to discredit someone you don't even know!!

Dub makes his engines tighter than most because people are willing to pay extra for better machine work. He also expects more power from his engines and makes the bore taper greater and the piston / cylinder clearance tighter than most mass produced engines.

He considers an engine's piston / cylinder to be worn out long before the average Joe does. But he is looking for the most power he can get while the guy with the little TT .46 is happy as long as the engine starts and runs fairly well long after the piston is loose and that "bump' is gone on the compression stroke!!

http://208.56.133.144/tech/breakin.html

That is the link to Dub's page on breaking in his engines.

Here is some of what YOU chose to leave out!!

'Breaking in your Jett: Put your engine on a test stand!!!. You pay a lot of money for your engines and airplanes. You must spend a bit more time and money to get the engine operating well before you fly. "

"Start the engine at full or part throttle, but not at idle. As quickly as possible, move behind the engine (never stand in front of a running engine - see the safety instructions) and advance the throttle to full. "

"The engine should be RICH. Leave the battery on the glow plug for a while and let the engine run. After about one minute you my start to lean in the high speed needle and remove the glow plug battery. "

"For example, if your engine normally should turn a 10x6 APC at 17000, then you will run the engine during break-in at 17000 on a 9x6 propeller --- RICH. "

"The object is to run the engine for at least 30 minutes RICH, and at its proper RPM before it goes into the airplane. This will give you a chance to check out the throttle characteristics and get used to the engine. After the 30-min. test, then switch to your flying propeller and see if it operates properly.

The above was written by Dub Jett himself and is a lengthier version of what I indicated in my post!!

If your gonna post on the net, don't post half truths or miss-information. Some new guy could go out and ruin his new engine by just following the impression your post left!

CK

OK, you're both right...but Dubb Jett is VERY right! DJ has probably forgot more about engines than we'll ever know!

downunder's quote of DJ is not discrediting you in any manner, merely pointing out that the major point in a break-in is to get the rod/crank fitted. Yes, the piston/sleeve fit is critical, but the rod/crank fit is what DJ considers to be the main point of break-in.

Gunshipgunner...I certainly wasn't meaning to imply that your post was inaccurate or that engines don't need running in. They do, and what you'd written covered it quite well as far as the piston/liner goes. I was merely pointing out that one thing that's generally overlooked is the necessity of running in the con rod as well and so I used the quote from Jett Engineering as an acknowledged expert in the field. However, in the interests of brevity I only quoted the relevant part to correct your statement that the lower end doesn't need running in.
Let's not have a bad hair day over this

Running in is a very weird science, my MVVS 40 took AGES! but now its one of the best engines i have. if you have a MDS, just fly it right out the box, you'll only half its life with those 3 tanks, any MDS engine thats still running in our club, never got ran in.
i have 2 Magnum 36's one ran 6 tanks though, and treated nice in a fun fly, the other had 1 tank then put on a mini pipe and screamed about in a fast delta, the 6 tanks has no compression and is useless, the other is good as new.
I'm not saying dont run in engines, you have to do sommit, unless its a MDS and then its your own fault for buying it.
Best thing is ask someone whos got one, and treat it gentle for a few runs.
The fuel we're using is Weston UK Liquid Gold, non of that nasty castor stuff in it, i guess that has a diffrence on how ours break in, probably quicker.

I see the question of break in come up a lot and there are always several reply's to how to break in this or that engine. So my question is why don't folks just follow the instructions that came with the engine? I don't claim to be an expert but I assume the folks that build the engine are on their engine. I buy an OS engine I use the procedure in the OS manual, Jett engine - Jett procedure etc.

Is there any objective data to show one break in procedure is better worse or equal to another?

This would be a good project for a magazine. Buy the same engine, break them in several different ways live with them for a year or so and compare the results. They do this kind of thing in Car magazines, why can't one of the model mags give us the same kind of reporting?

Kent

P.S. I'm not trying to say that anyone is providing any wrong or harmful information, I'm just thinking we need more objective information.