Front bearing air leak..

Front bearing air leak..
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Front bearing air leak.. - 6/26/2008 3:17:12 AM

tcv_racing

Posts: 137
Joined: 3/28/2008
From: zama, JAPAN
Status: offline

I did an air leak test using soapy water and found an air leak in the front bearing..

-Is it normal for the front bearing to leak air when the engine is cold?
because I read in another forum that during engine running temps (220-250 deg.) the front bearing expands therefore preventing an air leak..

-Or it doesn't matter if the engine is cold or in running temp, as long as there is an air leak its time for the front bearing to be changed?

Thanks in advance!

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RE: Front bearing air leak.. - 6/26/2008 3:54:30 AM

SManMTB

Posts: 4834
Joined: 4/28/2005
From: Charlottesville, VA, USA
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A small leak is no big deal. It should actually leak some to get lubricated.

(in reply to tcv_racing)

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RE: Front bearing air leak.. - 6/26/2008 4:43:18 AM

cold_reboot

Posts: 241
Joined: 1/22/2008
From: Eustace, TX, USA
Status: offline

Yup, front bearing leak is pretty normal. It'll expand when it heats up when running the engine. No worries. Kinda like the old SR-71 Blackbird spyplanes. Those planes sitting on the ground leaked like a sponge cereal bowl. When they were flying subsonic the metal (skin and everything else) would get so hot (several hundred degrees) from friction with the air the whole plane would tighten up. Same principal.

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Caster Racing K8T, TTR ST-1, Spektrum DSM

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RE: Front bearing air leak.. - 6/26/2008 5:18:29 AM

stussman

Posts: 223
Joined: 6/5/2007
From: Gold Coastqld, AUSTRALIA
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If the engine is still running normal i wouldnt worry about it. But if its tune is all over the shop, running hot etc, change your bearing.

(in reply to cold_reboot)

Post #: 4

RE: Front bearing air leak.. - 6/26/2008 1:55:13 PM

slayerphonics

Posts: 2092
Joined: 3/2/2007
From: Daytona Beach, FL, USA
Status: offline

quote:

ORIGINAL: tcv_racing

I did an air leak test using soapy water and found an air leak in the front bearing..

-Is it normal for the front bearing to leak air when the engine is cold?
because I read in another forum that during engine running temps (220-250 deg.) the front bearing expands therefore preventing an air leak..

-Or it doesn't matter if the engine is cold or in running temp, as long as there is an air leak its time for the front bearing to be changed?

Thanks in advance!

Ya don't sweat the front bearing leaking when the engine is cold, Thats normal. But it shouldn't be so bad that when the engine is running it is affecting your tune.

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There's a right way and wrong way to do everything and the wrong way is trying to make everybody else do it the right way

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Post #: 5

RE: Front bearing air leak.. - 6/26/2008 2:45:38 PM

msg73

Posts: 28
Joined: 7/31/2004
From: , NJ, USA
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I also have an air leak in the front bearing and I have the usual issues...high temps, hard to tune, etc. (the engine ran fine when I first got it). I took out the bearing and can see light through the small gaps in the bearing. I'm waiting for my TKO ceramic bearing to arrive and hopefully that will help. I also did the soapy water test on the carb and back plate and there were no leaks.

(in reply to slayerphonics)

Post #: 6

RE: Front bearing air leak.. - 6/26/2008 3:05:36 PM

tcv_racing

Posts: 137
Joined: 3/28/2008
From: zama, JAPAN
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Thanks so much for all the replies..

The engine is still new, it only run less than 1 liter nitro..
The reason I checked for air leaks is because it went extremely hot while I was running, my temp guage measured 334 deg

Im not sure how bad the effect on the engine was, but I immediately turned the engine off anl let it cool down for a while, then when
it was cold enough I've tried running it again and it was fine, I can still notice the engines power.. I've richened the carb settings but
still it was running hot, 260-280 deg..

The only air leaks that I found was in the front bearing and in the rotary valve of the carb..
Since the front bearing is already eliminated from the list the only problem now is the rotary valve..
But the question is how can a rotary valve be air leak proof? A sealant cannot be applied to the valve since its a moving(rotating) part..

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HPI Firestorm 10T
Tamiya TT01 Rally

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RE: Front bearing air leak.. - 6/26/2008 6:15:54 PM

slayerphonics

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From: Daytona Beach, FL, USA
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Hmm, i've never used a rotary carb,

Can you post some pics of where you think its leaking at?

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There's a right way and wrong way to do everything and the wrong way is trying to make everybody else do it the right way

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Post #: 8

RE: Front bearing air leak.. - 6/26/2008 6:41:30 PM

tcv_racing

Posts: 137
Joined: 3/28/2008
From: zama, JAPAN
Status: offline

Here are the pics..

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Tamiya TT01 Rally

(in reply to slayerphonics)

Post #: 9

RE: Front bearing air leak.. - 6/26/2008 6:42:36 PM

cold_reboot

Posts: 241
Joined: 1/22/2008
From: Eustace, TX, USA
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What temps did it used to run? 260 to 280 isn't too hot. My TTR runs like poo till it gets to 250+ and settles in anywhere from 260 to 280 depending on how hard I'm running it. LRP is the same, except it wakes up at around 215 and tops out at about 260.

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Caster Racing K8T, TTR ST-1, Spektrum DSM

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RE: Front bearing air leak.. - 6/26/2008 10:28:54 PM

tcv_racing

Posts: 137
Joined: 3/28/2008
From: zama, JAPAN
Status: offline

well I use to run around 260-270 on the leanest carb setting possible without getting a bog..
I only started to suspect an air leak just a few days ago while driving on dirt when my temps hit 334 degrees..
But I'll be trying diffrent things like using cold plugs and lower percentage nitro with the current state of the engine
and see how things go..

Thanks again for all your replies!

_____________________________

HPI Firestorm 10T
Tamiya TT01 Rally

(in reply to cold_reboot)

Post #: 11

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