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Old 07-26-2010, 05:31 AM   #1
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Default Air leak front bearing. What to do?

I'm fairly certain the front bearing on my losi 454 motor is leaking enough to give me run away temps. Thing is the bearing is pretty new. Can I just replace the seal or put some goop on it?
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Old 07-26-2010, 05:48 AM   #2
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Replace it.
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Old 07-26-2010, 06:58 AM   #3
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Quote:
Originally Posted by blacksunshine View Post
Replace it.
Its like a half gallon old.
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Old 07-26-2010, 07:21 AM   #4
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If it needs to be replaced then it needs to be replaced, I have seen bad bearings, how do you know its leaking. I think they all of the oil coming out.
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Old 07-26-2010, 07:39 AM   #5
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Default High temps/front bearing

I don't beleive that this is causing your high temps.
Oil leakage from the front bearing is common, especially if you run the motor rich for extended periods.
High temps will be caused by your tune, or lack of airlow over the heatsink.
Do you think it is sucking air through the bearing seal? You will need to replace the bearing if this is the case.
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Last edited by tomdex; 07-26-2010 at 07:41 AM. Reason: Clarify point
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Old 07-26-2010, 07:40 AM   #6
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At only a half gallon, depending on the severity of the "leak" ( a little bit or a pool ?), it may just be the fact that it's not fully tuned or blubbery rich resulting in an overflow of excess unburnt fuel. If it's just high temps and not spitting fuel, it's most likely too lean somewhere for this stage of it's life combined with taking in air.

How does it run? Does it produce good smoke? In the next 1/4 to 1/2 gallon if it hasn't subsided I would look at taking the bearing out and installing a new. The 454 is basically a RTR engine, lacking quality in areas like bearings, I would look at a good quality ceramic like the TKO's.
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Old 07-26-2010, 07:40 AM   #7
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Front bearings do not provide air tight seal, they provide protection for dust/dirt going in the engine, if you have oil/fuel coming from that bearing, most probably it's due to a very rich bottom setting.....
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Old 07-26-2010, 07:41 AM   #8
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It's most likely the tune. A leaky bearing seal can cause the tune to float around but if the temps continue to ride then a few questions need to be asked:
1. does the performance degrade when the temps go up? If no then perhaps the temp gun is giving bad readings. When an engine runs too hot it also runs poorly
2. why do you think the bearing seal is "leaking"? The seal is not air nor water tight, if oil is pooling under it then there is oil pooling in the crankcase of the engine, again a tuning problem.

Id try richening the high speed needed a bit, then leaning the low speed needle until it runs well again. don't worry if you lose top speed for the time being, you're looking to get the balance right, tuning for speed comes after.

Edit: Wow, I started typing this response after Token's response.
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Old 07-26-2010, 07:47 AM   #9
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i'll try retuning again. This motor just doesn't want to run until it hits like 260F. I saw 293F after a 15 minute main. I don't even want to know what it was after my 30 min main. It always had smoke out of the corners. Its like if i fattened it up an hour on top it would run fat on the track and then i'd lean it an hour on top and it'd run good but hot. Maybe my bottom is lean but i just don't see how. I always tune the top first with the bottom obviously fat and once the top is dialed i tune the bottom for good punch and then set the idle stop. This isn't my first rodeo and the runaway temps just seem very airleaky to me.

I've got a B5 in the break in process now so the losi motor will only serve as a practice/backup to the b5. The b5 makes awesome power at 200F and holds a temp like a champ!
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Old 07-26-2010, 07:50 AM   #10
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If it's running well and making smoke, ignore the temp gun.

If you fatten the top you have to lean the bottom to get back to the same mixture because whatever the you do to the top end needle effects the bottom tune, they are in series.
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Old 07-26-2010, 08:28 AM   #11
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+1 on the puffin smoke and making power.Your also dealing with a 454 those engines are just shy of being a paper weight .Run it til it blows and throw it away...........
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Old 07-26-2010, 09:19 AM   #12
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Quote:
Originally Posted by blacksunshine View Post
+1 on the puffin smoke and making power.Your also dealing with a 454 those engines are just shy of being a paper weight .Run it til it blows and throw it away...........
Agreed. But it has 4 gallons on it and still has plenty of compression. I want to try and make it the best backup motor i can.
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Old 07-26-2010, 02:43 PM   #13
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Quote:
Originally Posted by tomdex View Post
I don't beleive that this is causing your high temps.
Oil leakage from the front bearing is common, especially if you run the motor rich for extended periods.
High temps will be caused by your tune, or lack of airlow over the heatsink.
Do you think it is sucking air through the bearing seal? You will need to replace the bearing if this is the case.
if you have a bad enough leak like i did which is what it sounds like... too much fuel goes out the front bearing creating it to run lean... and the more you richen the leaner you get
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Old 07-27-2010, 01:59 AM   #14
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Default Front Bearing

I thought my front bearing was leaking and was having a tuff time tuning my os 12tz 3 port. I replaced the bearing and while at it I ported and polished the sleeve. It turns out I had a crack at the bottom of the fuel tank right in the middle. By the way @180 deg. it run runs like a raped ape! P.S. crack kills

Last edited by ramjesr; 07-27-2010 at 02:12 AM.
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Old 07-28-2010, 01:35 PM   #15
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Quote:
Originally Posted by 808gx7r View Post
too much fuel goes out the front bearing creating it to run lean... and the more you richen the leaner you get

No no no no no no... hold it here for a few seconds... If the front bearing actually IS leaking that means you get TOO MUCH AIR in the engine.
Not the other way around with to much fuel going OUT of the engine.

It's simple: IF the bearing leaks too much you get air into the engine in two ways.
1. Air through the carburator bringing fuel along with it.
2. Air through the front bearing NOT bringing fuel along with it.
And this equals a lean condition with high temps and bad performance!
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