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Why not let engine run out of fuel during break-in?

Why not let engine run out of fuel during break-in?

Old 05-19-2014, 01:05 AM
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Default Why not let engine run out of fuel during break-in?

Why is it important to not let an engine run out of its fuel during the tank idle break-in?

I already know not to let it happen but I don't know why.

I know it starts to run lean when it's on its last drops but is that a big problem? If so, what does it do to the engine?
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Old 05-19-2014, 01:14 AM
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It can cause the engine to rev higher than needed and also can starve the engine of oil.
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Old 05-19-2014, 01:31 AM
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It's bad for a lot of reasons, mainly because your basically burning off everything inside of the engine and with tight tolerances the new engine has it can cause any off the further issues from least likely to less likely, plug failure, sucking in of the glow plug coil which can lead to damage of piston or sleeve liner (scaring/scratching) or rear bearing failure from rod not getting any oil and causing rod bushings to break apart in engine that can cause the bearing to fall apart and destroy the entire engine (happened to me twice) rod could snap from tight tolerance no oil and engine revving up while leaning out. Its a tricky situation because you don't want to leave an engine full of fuel if your not going to use it but you don't want to deal with that lean sound cause it doesn't sound good so your best bet is to have your after run oil. When an engine has less compression it's not as bad to do but you always risk the coil sucking in which is a 1-500 odds chance of happening. If I even remotely here my engine leaning out I stop and hold the breaks if I'm on the track, if I'm on the starter box I just pinch the fuel line and slightly cover the exhaust so it doesn't rev up crazy but still gets empty.
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Old 05-19-2014, 02:18 AM
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Not a big deal IMO.. Break-in settings should be rich enough, and you're not revving it anyway. Non-issue for the most part - at least for normal heat-cycling...
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Old 05-21-2014, 02:08 PM
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They say you're not suppose to but I have been for years. I have not seen or had any issues with engines. You're not reving the engine nor is it high RPM...
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Old 05-21-2014, 03:11 PM
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There is no issue with running the engine out of fuel during break-in or otherwise. This is one of the biggest urban legends in RC, in my experience anyhow... ;o)
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Old 05-21-2014, 03:52 PM
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It is not about the possible issues. I have seen engines with large deep scratches on the piston perfectly running with no issues.

But when running in an engine you want to have it perfect so without any scratches on the piston. To get that perfect piston you must avoid any possible damages.
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Old 05-21-2014, 08:09 PM
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it depend on the fuel. some are better than others as far as protection. I always ran my engines out but changed do to random issues. Now I leave fuel by stopping the clutch never run dry.
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Old 05-21-2014, 10:49 PM
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I personally don't do it. In the past if I had a plug blow prematurely it was because I let the truck run out of fuel. My motivation to stop running it dry were the $8 glow plugs.
Another thing I stopped doing is stalling /killing the engine by blocking the exhaust. That killed plugs often as well.
That was years ago. Now my plugs last so long I just change them because they've been used for so long.

Any I wouldn't run it dry to be safe. Plus I rather fuel the truck in front of me instead of walking out and carrying it back to fuel it.
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Old 05-22-2014, 10:36 AM
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Originally Posted by Franchise View Post
I personally don't do it. In the past if I had a plug blow prematurely it was because I let the truck run out of fuel. My motivation to stop running it dry were the $8 glow plugs.
Another thing I stopped doing is stalling /killing the engine by blocking the exhaust. That killed plugs often as well.
That was years ago. Now my plugs last so long I just change them because they've been used for so long.

Any I wouldn't run it dry to be safe. Plus I rather fuel the truck in front of me instead of walking out and carrying it back to fuel it.
So blocking the exhaust is a bad way to stop the engine?

I don't like pinching the fuel line because that seems to make it sound like it's running lean.

What's the best way to stop the engine?
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Old 05-22-2014, 10:38 AM
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Originally Posted by bigjayjay1 View Post
it depend on the fuel. some are better than others as far as protection. I always ran my engines out but changed do to random issues. Now I leave fuel by stopping the clutch never run dry.
How do you stop the clutch? Or do you mean flywheel?

Either way, I'm wondering what's the best way to stop the engine.
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Old 05-22-2014, 10:40 AM
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Originally Posted by mercfocus View Post
So blocking the exhaust is a bad way to stop the engine?

I don't like pinching the fuel line because that seems to make it sound like it's running lean.

What's the best way to stop the engine?
Use the back of a screw driver or your shoe on the flywheel. I have always used my thumb and have never burned it but my idle is low and I have been tuning for 10+ years. Go in from the bottom of the chassis and just stop the flywheel.
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Old 05-22-2014, 10:41 AM
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Tip of your shoe on the flywheel.
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Old 05-22-2014, 10:51 AM
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Originally Posted by SteveP View Post
There is no issue with running the engine out of fuel during break-in or otherwise. This is one of the biggest urban legends in RC, in my experience anyhow... ;o)
So far, I'm thinking I havn't had any issues either but then again, I've never had an engine last past 3 gallons before. I sold my last engines several years ago before I could see how long they would last.

Now I'm breaking in a Nava Rossi Beat 5 and it ran out of fuel on the first tank. I didn't realize it was out of fuel already. Caught me by surprise.

This is my first really "high-end" engine so I want it to be perfect. Or as close to perfect as I can get it.
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Old 05-22-2014, 01:20 PM
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Same reason you wouldn't want to run your own car without oil, if you let it run out the engine has much less lubrication for a second or two.
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