Bearing replacement problem

Bearing replacement problem

Post by Brad Jense » Thu, 06 Dec 2001 10:29:50



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I ordered a new bearing kit from Boca Bearings for my ST 90.   The bearings
I recieved are the same physical size,  but the seal on the front bearing is
different.   The original bearing had a sealed bearing type seal on one side
and nothing on the other.    The replacement bearing I recieved had only
dust cover type seals ( not really sealed.    On the old bearing,  I can not
blow air thru the seal,  on the new one I can.

Will I have a problem with this new bearing and engine performance?    Has
anybody had any experience with these bearings and this motor?   I ordered
the econo-power bearing kit.

--

Brad Jensen

The only reason I am here, is because I am not all there.

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Bearing replacement problem

Post by Iron » Thu, 06 Dec 2001 11:00:31


Your going to suck some major air.  My bro-in-law had a bad bearing on his
MDS and it ran like total ***until he replaced it.

IronZ


Quote:
> **** Post for FREE via your newsreader at post.usenet.com ****

> I ordered a new bearing kit from Boca Bearings for my ST 90.   The
bearings
> I recieved are the same physical size,  but the seal on the front bearing
is
> different.   The original bearing had a sealed bearing type seal on one
side
> and nothing on the other.    The replacement bearing I recieved had only
> dust cover type seals ( not really sealed.    On the old bearing,  I can
not
> blow air thru the seal,  on the new one I can.

> Will I have a problem with this new bearing and engine performance?    Has
> anybody had any experience with these bearings and this motor?   I ordered
> the econo-power bearing kit.

> --

> Brad Jensen

> The only reason I am here, is because I am not all there.

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
>                       http://www.FoundCollection.com/
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=


 
 
 

Bearing replacement problem

Post by John Hawkin » Thu, 06 Dec 2001 12:04:25


        One shield on the outside of the front bearing is the most
common  configuration for model engines.  The shield is to keep dirt
out of the bearing and not to seal up the engine.  There is a net
positive pressure on the inner side of the front bearing.  The seal
for the front of the engine is achieved through a close running fit
between the crank and the case.  In cases where this clearance is
excessive a seal may provide symptomatic relief for a period of time.
In any event these type of seals are meant to keep lubricant in and
dirt out rather than to seal against pressure.

On Tue, 4 Dec 2001 19:29:50 -0600, "Brad Jensen"

Quote:

>**** Post for FREE via your newsreader at post.usenet.com ****

>I ordered a new bearing kit from Boca Bearings for my ST 90.   The bearings
>I recieved are the same physical size,  but the seal on the front bearing is
>different.   The original bearing had a sealed bearing type seal on one side
>and nothing on the other.    The replacement bearing I recieved had only
>dust cover type seals ( not really sealed.    On the old bearing,  I can not
>blow air thru the seal,  on the new one I can.

>Will I have a problem with this new bearing and engine performance?    Has
>anybody had any experience with these bearings and this motor?   I ordered
>the econo-power bearing kit.

John Hawkins -  From Canada's Atlantic Coast
 
 
 

Bearing replacement problem

Post by Mike Norto » Thu, 06 Dec 2001 12:15:35


I had a Supertigre .75 and got the same lack of seals from Boca.  As a
result, the engine would not stop running with the throttle closed all of
the way due to air leaking in around the front bearing..  Since the original
front bearing was in reasonable shape, I put it back in.  It works now.

Quote:
> One shield on the outside of the front bearing is the most
> common  configuration for model engines.  The shield is to keep dirt
> out of the bearing and not to seal up the engine.  There is a net
> positive pressure on the inner side of the front bearing.  The seal
> for the front of the engine is achieved through a close running fit
> between the crank and the case.  In cases where this clearance is
> excessive a seal may provide symptomatic relief for a period of time.
> In any event these type of seals are meant to keep lubricant in and
> dirt out rather than to seal against pressure.

> On Tue, 4 Dec 2001 19:29:50 -0600, "Brad Jensen"

> >**** Post for FREE via your newsreader at post.usenet.com ****

> >I ordered a new bearing kit from Boca Bearings for my ST 90.   The
bearings
> >I recieved are the same physical size,  but the seal on the front bearing
is
> >different.   The original bearing had a sealed bearing type seal on one
side
> >and nothing on the other.    The replacement bearing I recieved had only
> >dust cover type seals ( not really sealed.    On the old bearing,  I can
not
> >blow air thru the seal,  on the new one I can.

> >Will I have a problem with this new bearing and engine performance?
Has
> >anybody had any experience with these bearings and this motor?   I
ordered
> >the econo-power bearing kit.

> John Hawkins -  From Canada's Atlantic Coast

 
 
 

Bearing replacement problem

Post by Bill Fulme » Thu, 06 Dec 2001 22:24:00


Sorry...  Yer right about an MDS sucking, but it won't be thru the front
bearing...  Crankcase pressure is positive at this point..  Worst case would
be a "wet nose"...

Cheers,

Bill


Quote:
> Your going to suck some major air.  My bro-in-law had a bad bearing on his
> MDS and it ran like total ***until he replaced it.

> IronZ



> > **** Post for FREE via your newsreader at post.usenet.com ****

> > I ordered a new bearing kit from Boca Bearings for my ST 90.   The
> bearings
> > I recieved are the same physical size,  but the seal on the front
bearing
> is
> > different.   The original bearing had a sealed bearing type seal on one
> side
> > and nothing on the other.    The replacement bearing I recieved had only
> > dust cover type seals ( not really sealed.    On the old bearing,  I can
> not
> > blow air thru the seal,  on the new one I can.

> > Will I have a problem with this new bearing and engine performance?
Has
> > anybody had any experience with these bearings and this motor?   I
ordered
> > the econo-power bearing kit.

> > --

> > Brad Jensen

> > The only reason I am here, is because I am not all there.

> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> >  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
> >                       http://www.FoundCollection.com/
> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

 
 
 

Bearing replacement problem

Post by elb.. » Thu, 06 Dec 2001 22:29:59


Boca has a line of bearings called the "Ultra" series that have seals
front and back. There is also a Series of bearings with a seal on one
side only.

If you reorder tell them you need a sealed front bearing and specify
single sided or double sided seal. Oh course, it will cost more than
the standard bearing with only a dust covers.

I think it costed a few bucks more for the set to get a sealed front
bearing when I replaced the bearings in my Saito .65 a couple year
ago.



Quote:
>I had a Supertigre .75 and got the same lack of seals from Boca.  As a
>result, the engine would not stop running with the throttle closed all of
>the way due to air leaking in around the front bearing..  Since the original
>front bearing was in reasonable shape, I put it back in.  It works now.


>> One shield on the outside of the front bearing is the most
>> common  configuration for model engines.  The shield is to keep dirt
>> out of the bearing and not to seal up the engine.  There is a net
>> positive pressure on the inner side of the front bearing.  The seal
>> for the front of the engine is achieved through a close running fit
>> between the crank and the case.  In cases where this clearance is
>> excessive a seal may provide symptomatic relief for a period of time.
>> In any event these type of seals are meant to keep lubricant in and
>> dirt out rather than to seal against pressure.

>> On Tue, 4 Dec 2001 19:29:50 -0600, "Brad Jensen"

>> >**** Post for FREE via your newsreader at post.usenet.com ****

>> >I ordered a new bearing kit from Boca Bearings for my ST 90.   The
>bearings
>> >I recieved are the same physical size,  but the seal on the front bearing
>is
>> >different.   The original bearing had a sealed bearing type seal on one
>side
>> >and nothing on the other.    The replacement bearing I recieved had only
>> >dust cover type seals ( not really sealed.    On the old bearing,  I can
>not
>> >blow air thru the seal,  on the new one I can.

>> >Will I have a problem with this new bearing and engine performance?
>Has
>> >anybody had any experience with these bearings and this motor?   I
>ordered
>> >the econo-power bearing kit.

>> John Hawkins -  From Canada's Atlantic Coast

 
 
 

Bearing replacement problem

Post by Propwo » Fri, 07 Dec 2001 01:14:06


I rebuild most of the engines in our club and surronding areas and all
I ever do is go to the local bearing company with the old bearings and
they supply repalcements that are exact. Never had a problem. The only
time they could not find the proper bearing is for the rear bearing on
a YS. Its a Nachi and is very narrow and even Nachi claimes its built
just for YS. If it comes with seals on both sides just use something
sharp to gently pierce the one side and pry out the seal. Try it on
the old seal to see how easy it is to remove the seals.

On Wed, 5 Dec 2001 07:24:00 -0600, "Bill Fulmer"

Quote:

>Sorry...  Yer right about an MDS sucking, but it won't be thru the front
>bearing...  Crankcase pressure is positive at this point..  Worst case would
>be a "wet nose"...

>Cheers,

>Bill



>> Your going to suck some major air.  My bro-in-law had a bad bearing on his
>> MDS and it ran like total ***until he replaced it.

>> IronZ



>> > **** Post for FREE via your newsreader at post.usenet.com ****

>> > I ordered a new bearing kit from Boca Bearings for my ST 90.   The
>> bearings
>> > I recieved are the same physical size,  but the seal on the front
>bearing
>> is
>> > different.   The original bearing had a sealed bearing type seal on one
>> side
>> > and nothing on the other.    The replacement bearing I recieved had only
>> > dust cover type seals ( not really sealed.    On the old bearing,  I can
>> not
>> > blow air thru the seal,  on the new one I can.

>> > Will I have a problem with this new bearing and engine performance?
>Has
>> > anybody had any experience with these bearings and this motor?   I
>ordered
>> > the econo-power bearing kit.

>> > --

>> > Brad Jensen

>> > The only reason I am here, is because I am not all there.

>> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>> >  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
>> >                       http://www.FoundCollection.com/
>> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

 
 
 

Bearing replacement problem

Post by Paul McIntos » Fri, 07 Dec 2001 02:53:38


The rear bearings for YS four strokes are readily available and a standard
size.  Email me if you need the specifics.

--
Paul McIntosh
Desert Sky Model Aviation
ARFs, engines, bearings, etc
http://www.FoundCollection.com/

Quote:
> I rebuild most of the engines in our club and surronding areas and all
> I ever do is go to the local bearing company with the old bearings and
> they supply repalcements that are exact. Never had a problem. The only
> time they could not find the proper bearing is for the rear bearing on
> a YS. Its a Nachi and is very narrow and even Nachi claimes its built
> just for YS. If it comes with seals on both sides just use something
> sharp to gently pierce the one side and pry out the seal. Try it on
> the old seal to see how easy it is to remove the seals.

> On Wed, 5 Dec 2001 07:24:00 -0600, "Bill Fulmer"

> >Sorry...  Yer right about an MDS sucking, but it won't be thru the front
> >bearing...  Crankcase pressure is positive at this point..  Worst case
would
> >be a "wet nose"...

> >Cheers,

> >Bill



> >> Your going to suck some major air.  My bro-in-law had a bad bearing on
his
> >> MDS and it ran like total ***until he replaced it.

> >> IronZ



> >> > **** Post for FREE via your newsreader at post.usenet.com ****

> >> > I ordered a new bearing kit from Boca Bearings for my ST 90.   The
> >> bearings
> >> > I recieved are the same physical size,  but the seal on the front
> >bearing
> >> is
> >> > different.   The original bearing had a sealed bearing type seal on
one
> >> side
> >> > and nothing on the other.    The replacement bearing I recieved had
only
> >> > dust cover type seals ( not really sealed.    On the old bearing,  I
can
> >> not
> >> > blow air thru the seal,  on the new one I can.

> >> > Will I have a problem with this new bearing and engine performance?
> >Has
> >> > anybody had any experience with these bearings and this motor?   I
> >ordered
> >> > the econo-power bearing kit.

> >> > --

> >> > Brad Jensen

> >> > The only reason I am here, is because I am not all there.

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> >> >  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
> >> >                       http://www.FoundCollection.com/

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

 
 
 

Bearing replacement problem

Post by John Hawkin » Fri, 07 Dec 2001 03:23:26


        Bearings from the local bearing supply house will often work
but in some applications they will have shortened life due to
inadequate internal clearance.  For model engines a C3 clearance is
best.  This is looser than the standard clearance that you get if none
is specified.  You may get away with standard fit in some engines but
with others you won't.  Your shop can probably supply in C3 in many
sizes.  A couple cases where I have found where the tighter bearings
fail quickly are Webra Speed61 and OS1.08.

        I believe the tightness of the fit of the outer race in the
case and the heat expansion characteristics of the engine are a couple
things that affect bearing clearance requirements.



Quote:
>I rebuild most of the engines in our club and surronding areas and all
>I ever do is go to the local bearing company with the old bearings and
>they supply repalcements that are exact. Never had a problem. The only
>time they could not find the proper bearing is for the rear bearing on
>a YS. Its a Nachi and is very narrow and even Nachi claimes its built
>just for YS. If it comes with seals on both sides just use something
>sharp to gently pierce the one side and pry out the seal. Try it on
>the old seal to see how easy it is to remove the seals.

>On Wed, 5 Dec 2001 07:24:00 -0600, "Bill Fulmer"

>>Sorry...  Yer right about an MDS sucking, but it won't be thru the front
>>bearing...  Crankcase pressure is positive at this point..  Worst case would
>>be a "wet nose"...

>>Cheers,

>>Bill



>>> Your going to suck some major air.  My bro-in-law had a bad bearing on his
>>> MDS and it ran like total ***until he replaced it.

>>> IronZ



>>> > **** Post for FREE via your newsreader at post.usenet.com ****

>>> > I ordered a new bearing kit from Boca Bearings for my ST 90.   The
>>> bearings
>>> > I recieved are the same physical size,  but the seal on the front
>>bearing
>>> is
>>> > different.   The original bearing had a sealed bearing type seal on one
>>> side
>>> > and nothing on the other.    The replacement bearing I recieved had only
>>> > dust cover type seals ( not really sealed.    On the old bearing,  I can
>>> not
>>> > blow air thru the seal,  on the new one I can.

>>> > Will I have a problem with this new bearing and engine performance?
>>Has
>>> > anybody had any experience with these bearings and this motor?   I
>>ordered
>>> > the econo-power bearing kit.

>>> > --

>>> > Brad Jensen

>>> > The only reason I am here, is because I am not all there.

>>> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>>> >  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
>>> >                       http://www.FoundCollection.com/
>>> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

John Hawkins -  From Canada's Atlantic Coast
 
 
 

Bearing replacement problem

Post by Paul McIntos » Fri, 07 Dec 2001 05:25:52


Dead on, John.  Nearly all model bearings are at least C3 clearance.  Some
real hot engines are even looser.  Also, be sure that you get ABEC 3 or
better tolerance bearings as ABEC 1 bearings can be far enough out of
tolerance in the outer ring that you may not be able to properly install
them.  Both of these ratings go hand in hand.

--
Paul McIntosh
Desert Sky Model Aviation
ARFs, engines, bearings, etc
http://www.FoundCollection.com/

Quote:
> Bearings from the local bearing supply house will often work
> but in some applications they will have shortened life due to
> inadequate internal clearance.  For model engines a C3 clearance is
> best.  This is looser than the standard clearance that you get if none
> is specified.  You may get away with standard fit in some engines but
> with others you won't.  Your shop can probably supply in C3 in many
> sizes. A couple cases where I have found where the tighter bearings
> fail quickly are Webra Speed61 and OS1.08.

> I believe the tightness of the fit of the outer race in the
> case and the heat expansion characteristics of the engine are a couple
> things that affect bearing clearance requirements.



> >I rebuild most of the engines in our club and surronding areas and all
> >I ever do is go to the local bearing company with the old bearings and
> >they supply repalcements that are exact. Never had a problem. The only
> >time they could not find the proper bearing is for the rear bearing on
> >a YS. Its a Nachi and is very narrow and even Nachi claimes its built
> >just for YS. If it comes with seals on both sides just use something
> >sharp to gently pierce the one side and pry out the seal. Try it on
> >the old seal to see how easy it is to remove the seals.

> >On Wed, 5 Dec 2001 07:24:00 -0600, "Bill Fulmer"

> >>Sorry...  Yer right about an MDS sucking, but it won't be thru the front
> >>bearing...  Crankcase pressure is positive at this point..  Worst case
would
> >>be a "wet nose"...

> >>Cheers,

> >>Bill



> >>> Your going to suck some major air.  My bro-in-law had a bad bearing on
his
> >>> MDS and it ran like total ***until he replaced it.

> >>> IronZ



> >>> > **** Post for FREE via your newsreader at post.usenet.com ****

> >>> > I ordered a new bearing kit from Boca Bearings for my ST 90.   The
> >>> bearings
> >>> > I recieved are the same physical size,  but the seal on the front
> >>bearing
> >>> is
> >>> > different.   The original bearing had a sealed bearing type seal on
one
> >>> side
> >>> > and nothing on the other.    The replacement bearing I recieved had
only
> >>> > dust cover type seals ( not really sealed.    On the old bearing,  I
can
> >>> not
> >>> > blow air thru the seal,  on the new one I can.

> >>> > Will I have a problem with this new bearing and engine performance?
> >>Has
> >>> > anybody had any experience with these bearings and this motor?   I
> >>ordered
> >>> > the econo-power bearing kit.

> >>> > --

> >>> > Brad Jensen

> >>> > The only reason I am here, is because I am not all there.

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> >>> >  *** Usenet.com - The #1 Usenet Newsgroup Service on The Planet! ***
> >>> >                       http://www.FoundCollection.com/

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

> John Hawkins -  From Canada's Atlantic Coast

 
 
 

Bearing replacement problem

Post by DBusk58 » Mon, 10 Dec 2001 12:01:35


Brad,You need a bearing that will seal completely at the outside of the
crankcase or you will have a no-start condition..
Buzz.
 
 
 

Bearing replacement problem

Post by John Hawkin » Mon, 10 Dec 2001 21:30:41


        Gee Buzz, both my ST90's start up fine without sealed front
bearings.  I guess there must be something wrong with them, eh?


Quote:
>Brad,You need a bearing that will seal completely at the outside of the
>crankcase or you will have a no-start condition..
>Buzz.

John Hawkins -  From Canada's Atlantic Coast