I have a B-25 that has two Evolution .36 engines on it. I have been told that Evolution engines don't require break in but I decided to run a couple of tanks through them first any-way. One of them runs great and has good response and idle but the other is alot tighter to turn and takes a little longer to idle down, and doesn't take the gas like it's partner. It opens up and runs good at top end but I noticed that it has a knock when turned by hand at top dead center. It also seems to have more compression than the other. I think, or hope, that it just requires more of a "break in" but I decided to ask you out there. I have had engines that do require break-in that were tight like this one and had the same type of knock at the TDC that this one does. The no break in thing is something that is new to me. Do they do the break in at the factory or what? If so maybe they skipped this one. I definately won't fly this twin with them like this! Advice? By the way. I have ran 4 tanks through them as of now and intend in running more when I can go get some. Twins can suck up some fuel quick!

James,


Even though this engine is stated not to actually require a formal break-in, follow the procedure described in [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]this thread[/link], and your engine will last optimally.

You think they will even out to the same performance then? After the break in that is.

James,


Two engines that were manufactured identically (CNC) and broken-in in the same manner, should perform similarly...

However, one of your engines is tighter than the other one is...
See why. I suspect a bearing may be unseated, causing the crank to rub on the back-plate...


I obviously cannot guarantee the break-in will even them out...
Contact Horizon and describe the problem you're seeing - stating both engines must be mounted on a twin.

See what they will do.

Kind of what I was thinking. I pulled the plugs after I talked to you last and the only thing I can tell different is the pinch in one is way more than the other. Bearings in both feel great. Still un-easy though. I won't trust them untill they are identical. I guess I will run more fuel through them. At least the tight one any-way. I thought that "No break in" stuff was bull to start with. I want to know what mine are going to do before I take-off. Espeacially on a twin. I will drop a line to horizon. Thanks!

I've heard this story before that Evolution engines don't need to be run in. Don't believe it!! They may (although I doubt it) have been given a quick run at the factory but certainly not run in.

It seems that your suspect engine has just got a much tighter pinch at TDC than the other so just chuck it on the test stand and give it some rich running until it settles down. Use some castor in the fuel too to help avoid any damage and keep checking the pinch after it's cooled down at the end of maybe a 3 to 5 minute run (at full throttle of course).

I would say there is no need to contact Horizon right now. Just run some fuel through them both. They need some wide open time. I wouldn't bother with heat cycling them, or anything like that.

You didn't say what fuel you are using. Try 15% and stick with that. Also, ditch the plugs that you used to break them in and put in OS A3s.

Evolution did claim for a short time that each engine was run on the bench at the factory. They dropped the claim pretty early on.

What the other guys said. Just don't run it too rich and cold. If you can just barely hold a finger on the head with a good smoke stream, that's about right for wide open run-in. If you hear the engine has a funny click-ity sound at idle, you know it's still tight and it's not at a good speed to let run at. Run it in some more, it will go away. On new or tight pinch engines, cold running and/or low speeds are hard on con rods and other parts and only extend the run-in process.