Go Back  R/C Tech Forums > General Forums > Nitro Off-Road
Air leaks in front bearing, normal? >

Air leaks in front bearing, normal?

Air leaks in front bearing, normal?

Old 06-16-2009, 06:13 AM
  #1  
Tech Regular
Thread Starter
iTrader: (30)
 
Cannondale1974's Avatar
 
Join Date: Mar 2008
Location: Lexington, Ky
Posts: 433
Trader Rating: 30 (100%+)
Default Air leaks in front bearing, normal?

I am in need potentially for a front bearing for a Sportwerks V2 engine. Wanted to confirm it's a 7x19x6? After doing a test for leaks the front bearing shows air escaping. (engine has approximately 2 gallons on it. ) I have another V2 with less than half a gallon and there's quite a bit of moisture around the flywheel as well.

I performed this test on a Novarossi P5X with 3 gallons and a GRP .21 tuned (brand new, never run) and they both show air escaping also from the front bearing. Is this normal or acceptable if the engine runs ok? Or is it necessary to purchase one of the double sealed, ceramic bearings (boca, TKO etc) to prevent this?

Thanks as always.
Cannondale1974 is offline  
Old 06-16-2009, 06:18 AM
  #2  
Tech Elite
 
Join Date: Mar 2009
Location: Aurora, Colorado
Posts: 4,055
Default

How are you testing these (GRP) if it was never run. Normally when you find theres a leak, Its from oil res coming out of the bearings not just air.
token is offline  
Old 06-16-2009, 06:22 AM
  #3  
Tech Regular
Thread Starter
iTrader: (30)
 
Cannondale1974's Avatar
 
Join Date: Mar 2008
Location: Lexington, Ky
Posts: 433
Trader Rating: 30 (100%+)
Default

I am sealing carb/exhaust with fingers, put soapy water around usual suspect areas that are prone to leak and blow into the fuel line. Air bubbles surface on the front bearing of all engines. The V2 with 1/2 gallon does have quite a bit of moisture around the flywheel/on the pipe however.

So I shouldn't worry about the air escaping, just fuel residue?

Thanks.
Cannondale1974 is offline  
Old 06-16-2009, 06:27 AM
  #4  
Tech Master
iTrader: (3)
 
Join Date: Feb 2008
Location: Ontario, Canada
Posts: 1,210
Trader Rating: 3 (100%+)
Default

When things heat up, they expand. Your test results would be a bit different in a running engine. When my front bearing went bad, there was fuel pouring out of it and it was impossible to tune. There was a puddle of fuel under the engine mounts after running it.
Semple is offline  
Old 06-16-2009, 06:30 AM
  #5  
Tech Master
iTrader: (8)
 
Gary NJ's Avatar
 
Join Date: Jan 2004
Location: Long Island NY
Posts: 1,157
Trader Rating: 8 (100%+)
Default

The front bearings in RC engines are not airtight by design. The front seal on the bearing is more to keep dirt out of the bearing, not air and fuel in the engine. The seal between the crank and the crankcase is mostly accomplished by fuel providing a 'wet seal' between the crank surface and the crankcase itself behind the front bearing when the engine is running and tuned correctly. The fit at that point between the crank and the crankcase is very close and precise. If the tune is too rich, especially on the bottom end, fuel can push out thru the front bearing. If you are pressure testing the engine statically, the front bearing will very rarely show a seal, even in a perfect engine. Sometimes, if you are checking an engine that has been stored with after run in it, it might seal even without running - but not usually. The engine/carb pressure tester I sell has a silicone rubber gasket to seal off the front bearing so the rest of the engine can be checked statically for leaks.

Other 2 stroke engines, like motorcycle and kart engines, use a separate oil seal that are outside of the bearings, and that seal the crankcase directly to the crank surface. There isn't enough room on an RC engine to use this type of seal.
Gary NJ is offline  
Old 06-16-2009, 06:31 AM
  #6  
Tech Elite
 
Join Date: Mar 2009
Location: Aurora, Colorado
Posts: 4,055
Default

Originally Posted by Cannondale1974 View Post
I am sealing carb/exhaust with fingers, put soapy water around usual suspect areas that are prone to leak and blow into the fuel line. Air bubbles surface on the front bearing of all engines. The V2 with 1/2 gallon does have quite a bit of moisture around the flywheel/on the pipe however.

So I shouldn't worry about the air escaping, just fuel residue?

Thanks.
Make sure its the bearing and not the carb or a leaky fuel hose. take off the flywheel and see if there is oily dirt build up under, but i would not worry about air.
token is offline  
Old 06-16-2009, 06:39 AM
  #7  
Tech Master
iTrader: (114)
 
2fst2c's Avatar
 
Join Date: Oct 2008
Location: Martin, MI
Posts: 1,939
Trader Rating: 114 (100%+)
Default

Originally Posted by Gary NJ View Post
The front bearings in RC engines are not airtight by design. The front seal on the bearing is more to keep dirt out of the bearing, not air and fuel in the engine. The seal between the crank and the crankcase is mostly accomplished by fuel providing a 'wet seal' between the crank surface and the crankcase itself behind the front bearing when the engine is running and tuned correctly. The fit at that point between the crank and the crankcase is very close and precise. If the tune is too rich, especially on the bottom end, fuel can push out thru the front bearing. If you are pressure testing the engine statically, the front bearing will very rarely show a seal, even in a perfect engine. Sometimes, if you are checking an engine that has been stored with after run in it, it might seal even without running - but not usually. The engine/carb pressure tester I sell has a silicone rubber gasket to seal off the front bearing so the rest of the engine can be checked statically for leaks.

Other 2 stroke engines, like motorcycle and kart engines, use a separate oil seal that are outside of the bearings, and that seal the crankcase directly to the crank surface. There isn't enough room on an RC engine to use this type of seal.
I don't see this engine/carb pressure tester you sell on your website. Kinda interested in it. PM me if you'd like. Thanks.
2fst2c is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.