R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro On-Road

Reply
 
Thread Tools Search this Thread
Old 06-29-2002, 08:24 AM   #1
Tech Initiate
 
Join Date: Jun 2002
Location: Tonteg, Wales, UK
Posts: 43
Post main bearings Help?

can someone please help have just rebuilt my thunder tiger pro .15 motor and fitted a new novarrosi slide carb. Have set all of the carb basic settings ( had them off the Paris racing site as suggested on an earlier post) the motor will not idle at a low enough idle speed even if I turn the idle speed screw below its minimum setting. I think the motor is drawing air ( induction leak) through the front or main bearings, have sealed the carb and backplate, and then sprayed WD40 on the front bearing whilst the motor is running to try and identify the problem. Motor slowed to an acceptable level and then cut out. Is this a common problem and is there any way I can seal the front bearing cranck area to cure the problem.
Raw40 is offline   Reply With Quote
Old 07-02-2002, 03:02 PM   #2
Tech Elite
 
Join Date: Aug 2001
Posts: 2,583
Default Re: main bearings Help?

Quote:
Originally posted by Raw40
can someone please help have just rebuilt my thunder tiger pro .15 motor and fitted a new novarrosi slide carb. Have set all of the carb basic settings ( had them off the Paris racing site as suggested on an earlier post) the motor will not idle at a low enough idle speed even if I turn the idle speed screw below its minimum setting. I think the motor is drawing air ( induction leak) through the front or main bearings, have sealed the carb and backplate, and then sprayed WD40 on the front bearing whilst the motor is running to try and identify the problem. Motor slowed to an acceptable level and then cut out. Is this a common problem and is there any way I can seal the front bearing cranck area to cure the problem.
There is no way to seal the front bearing since it needs to spin freely. You need to replace it if you suspect that it's bad. Is fuel leaking out of the front bearing?

Can you adjust the idle speed screw till the opening in the carb is closed? I ask because you mentioned below the minimum setting. You should be able to get the opening completely closed.
Sydewynder is offline   Reply With Quote
Old 07-02-2002, 03:20 PM   #3
Tech Initiate
 
Join Date: Jun 2002
Location: Tonteg, Wales, UK
Posts: 43
Default leaking

Hi sydewynder, yes I am able to close the slide all the way down and I have noticed oil/ fuel leaking from the front bearing onto the rear belt after a run.
Raw40 is offline   Reply With Quote
Old 07-02-2002, 03:29 PM   #4
Tech Elite
 
Join Date: Aug 2001
Posts: 2,583
Default

Hello Raw40

So you can close the carb opening all the way and the engine seems to be able to run and draw air in from somewhere? Checked the o-ring on all the needles plus the idle stop screw to see if any are cracked or damaged.

If there is excessive fuel leakage then I think you need to replace the front bearing. You should be able to tune the engine to run well with little or no fuel/oil leaking.

Is there much in and out and side to side play in the crankshaft when you wiggle it? (Engine not runnng please )

Last edited by Sydewynder; 07-02-2002 at 03:31 PM.
Sydewynder is offline   Reply With Quote
Old 07-02-2002, 03:58 PM   #5
Tech Initiate
 
Join Date: Jun 2002
Location: Tonteg, Wales, UK
Posts: 43
Post

Hi sydewynder, yes I have checked the O rings on the jets etc all seem to be ok, the axial endfloat on the crank is 0.007", radial is 0 the bearing looks as if it's in a reasonable conditon apart from having a steel dust seal would it be better if I try and get a bearing with rubber seal?
Raw40 is offline   Reply With Quote
Old 07-03-2002, 05:07 PM   #6
Tech Elite
 
Join Date: Aug 2001
Posts: 2,583
Default

Quote:
Originally posted by Raw40
Hi sydewynder, yes I have checked the O rings on the jets etc all seem to be ok, the axial endfloat on the crank is 0.007", radial is 0 the bearing looks as if it's in a reasonable conditon apart from having a steel dust seal would it be better if I try and get a bearing with rubber seal?

You can use rubber sealed bearings but someone who's an engine guru here (Motorman) said he's seen some where the rubber seal piece heated up and seized onto the crankshaft causing the shaft to fail. Even so, many manufacturers are using rubber seals now so I would give it a try. I looks like you've determined the bearing is bad by the WD40 spray test. Did you do a similar test on the backplate and carb?

Btw way, how's the crankshaft? The area around the front bearing and the journal where the window is? Is the journal damaged. Some engines such as the Novarossi design the crankshaft to help prevent oil leakage and maybe air leak.
Sydewynder is offline   Reply With Quote
Old 07-03-2002, 06:43 PM   #7
Tech Apprentice
 
Join Date: Feb 2002
Posts: 65
Default

if there isn't a brown mark on the crank where the bearing would rest i doubt its the bearing. Also there should be oil coming out of the front bearing, not alot but some.
Distroey is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
How do I replace the front and rear main bearings? rcjunky10 Nitro Off-Road 27 04-01-2008 08:10 PM
D-Main joe_jenkins Georgia Racing 8 02-05-2008 03:34 PM
FS HV Oil Pump, Rings, Main and Rod Bearings SBC hardey Other Items: For Sale/Trade or Wanted to Buy 1 06-22-2006 02:15 PM
KANZEN Bearings vs Boca Bearings vs Other Bearings rmdhawaii Nitro On-Road 6 04-29-2006 09:38 AM
Next Best Bearings To Ceramic Bearings????? J Smith Electric On-Road 47 08-21-2003 03:26 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -7. It is currently 01:46 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net