I just read the "manual" on the NR site. To my surprise they recommend a 30 minute break-in period, at low RPM. This is not what my previous (very limited) knowledge tell me about breaking in ABC engines.

I am ready to install two new NR91's and would like to break them in the right way.

One more question: Should they be broken in on a test stand or just by flying them a bit rich?

Thanks!!!

Ed

Ed,
I expect you will get lots of input on this......

By low RPM, I suspect low throttle setting is meant, rather than a richer than usual mix. The intent is to reduce loads on the rod during the first few minutes of run time.


You might consider removing the back plate and putting some oil directly on both ends of the rod before the first start; also, I have used my covering heat gun to evenly warm up the upper cylinder area before the first start. (NovaRossi Speed 13 engines)


I would definitely make the first runs on a test stand so that the process can be better controlled.

How tight is the piston fit on these engines?

I think there is a serious problem with the translation to English. If your NR engines are ABC break them in right. No less than 20% oil, prop them for flight rpm with at least 1" less prop. Run them at flight RPM with the mixture rich. After a tank of fuel, pinch the pressure line to lean to peak, and release to cool to rich mixture.

I am sure you know how to break in an ABC engine, but if you have any questions at all, shoot me a PM.

Scott

Ed,

As Scott points out, NovaRossi has had some translation issues in their documentation. I addressed this directly with them (during a review I wrote on the Speed/13) and they agreed that the English could stand a revision.

ABC engines should be broken in as such as already mentioned by others. Jim's suggestion of pre-lubing the rod bushings is a good one. If you don't touch the factory set carb it should start and run perfectly. If you have inflight needle adjustment, you should be able to just use that to control engine RPM (i.e., rich first tank or two) during test stand break-in. The engines will swallow a 16 oz tank in no time during the break-in runs. My engine was running perfectly after half a gallon of fuel.

I used Omega fuel with 3 oz of castor added per gallon. Once broken in, you can reduce the added castor slightly but the engines are so powerful that keeping them well lubed is not a bad idea for longevity.

David

Thanks Jim, Scott, David.

What you state is precisely how I understand an ABC engine should be broken in. Will proceed to do it.

Thanks!

Any updates?

Broke it in in the usual way, as we all knew. Not as indicated in the manual. Ran only three 16 oz tanks and it started idling and running pretty well. Installed in my Dirty Birdy to replace another NR 91F with worn bearings (as well as other parts).
Instant reward! Two flights, both with 150mph top speeds. WOW! Back to life!

13,800 with 15% nitro, OS8, APC 11.5x12.5N. Interesting to see that my Jett .90RE with same layout turns 13,900 (recently mounted on an MK Arrow). Both are truly "ballistic"

I need to run my Jett 90 someday.

The idle and transition on the Jett is most impressive

Truly Ballistic: >=140mph passes, full pattern capabilities (I know it's not the standard definition and that it even breaks some of the classic pattern standards, but the feeling is so good...)

My idea of a good pattern plane is one that can do a looooong slow roll down the runway and 125+ mph.

Close enough

Of course wheels up, prefer enclosed pipe and 18,000 rpm as well.

This morning: Wheels up, 105º, 155mph. This NR91 is outstanding!

A friend caught a glimpse on his iPhone

I'll try to get a longer shot on the next flight.

https://www.youtube.com/watch?v=UHGZeXHX8vU