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RE: Sometimes a deal ait't a deal! - 10/14/2003 12:33:50 PM   
ajcoholic



Posts: 4045
Joined: 6/22/2002
From: Kirkland Lake, ON, CANADA
Status: offline 		Dave,
I am not going to change your mind, and you wont change mine. However, I would like to clarify a few small points...

1- NEVER did I mention, ever, that a two stroke cycle engine will run "well" with a leak, any leak, anywhere. Dont put words into my mouth.

2- The fact that you didnt mention a worn crank to case seal is the exact problem we are talking about.

3- bearing sheilds are in fact on bearings to keep foreign matter out of the bearing! No ball bearings I know of are designed to act as a primary seal in a pressure setting. THATS what I said, not that dirt was going to get in from the front bearing on a FRV engine.


If an engine has (for numerous reasons, mainly poor fit to begin with, or worn fit due to ingestion or dirt or letting the bearings go and rubbing) an excess amount of space bewteen the crankcase and crankshaft, then it is worn out, plain and simple. A sealed bearing is NOT (no matter how much you want to believe it) going to completely seal the engine. Trust me, I have tried it and fuel WILL get past the bearing. Maybe you have some $100 bearing with super seals that are unavailable to us here in Canada, I dont know, but I do know that a rubber sealed bearing doesnt cure a leaky case - period.


So we agree to disagree... but thats it for me on this one.

AJC


_____________________________

Andrew J. Coholic
Engine reviewer for FLY RC Magazine - andrewc@flyrc.com

(in reply to Flyboy Dave)
       Post #: 26

RE: Sometimes a deal ait't a deal! - 10/14/2003 1:12:23 PM   
ZAGNUT



Posts: 2436
Joined: 2/26/2003
From: tel-aviv, ISRAEL
Status: offline 		well i think you guys are getting your terminology all mixed up! the term "sealed bearing" is just a bunch of hype used make you think you're getting a superior product. the actual bearing manufacturers call these rubber SHEILDS and not seals!

and Dave,
on my converted weedies i can usually get a little more rpm (100-150) when i toss the oil seals and use rubber sheided bearings in their place. the reduction in drag makes up for what little leakage i get around the crank.

dave

_____________________________

"I'll take the money- and you can have the rope"

(in reply to David_Moen)
       Post #: 27

RE: Sometimes a deal ait't a deal! - 10/14/2003 7:59:25 PM   
Flyboy Dave



Posts: 13518
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: online 		You might be right, Dave....we might be splitting unnecessary hairs here. Myself, Andrew and the others have only our own knowledge, experience, and opinions to go by....and they certainly can vary.....

Let me offer the experience I had with this engine.
A freind got it in a trade....a brand new Enya .60
The exhaust butterfly was missing, as well as the carb linkage.
I just happened to have the aluminum plugs for the exhaust flange, and a NOS OS .50FSR pipe that fit like a glove.

We fitted a carb off a Magnum .46 that was perfect as well.
We fired it up, but it would only run at full throttle....and
poorly at that. Fuel was pouring out the front so bad, you couldn't stand behind the engine.

I pulled the front off the motor, and it had a bare ball bearing
on it....and as it turned out....it was a real skinng one, that sat too far back into the case. I took that old front bearing from that OS .60 I pictured earlier, and trial fitted it to the front....it looked like like the right size, and it was still servicable. I pulled the motor down, and istalled the bearing....it was a metal shielded one, BTW.

Voila...it ran like a top. Admittedly....it was the only Enya I
have done, but it was new....you could see clearly indide
that the motor had never been run.

The point here is....the crank to crankcase fit....afforded
no sealing to the front of the engine whatsoever....in any
way, shape, or form.

It could not have been a better demonstration of how sealing
at the front of the engine will enhance the motors operation.

Again....I will offer, that the more airtight a two stroke motor
is....the better it will run.

Lets enjoy our areo-motors....(no hard feelings here), and
I wish "Good Flying To All ''....

Dave.

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_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to David_Moen)
       Post #: 28

RE: Sometimes a deal ait't a deal! - 10/14/2003 8:08:11 PM   
ajcoholic



Posts: 4045
Joined: 6/22/2002
From: Kirkland Lake, ON, CANADA
Status: offline 		Yes, no hard feelings - a debate is allways fun, as long as we all go away happy to have said our piece.

One more thing I was thinking about...

Now, if the case to crank fit IS worn, or poor to begin with, what effect does that have on proper closing and opening of the crankshaft rotory inlet valve? If fuel is leaking that badly past the crank, then surely air can be leaking both in and out of the inlet (past the poorly fit crank) and what effect does that have on the running?? Not good... And no front seal will fix that issue. As simple as these engines are they are allways a source of potential problems.

AJC


_____________________________

Andrew J. Coholic
Engine reviewer for FLY RC Magazine - andrewc@flyrc.com

(in reply to Flyboy Dave)
       Post #: 29

RE: Sometimes a deal ait't a deal! - 10/14/2003 8:27:23 PM   
Flyboy Dave



Posts: 13518
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: online 		Andrew....

....I really didn't check the fit of the crank....all I can say is
that it appeared to be normal....it didn't raise any red flags
as I handled the motor on the bearing refit....

....the motor did run down, and idle like a champ....even
though it had only a few minutes running time on it....so I
would have to think the fit was proper....

What did amaze me was the amount of fuel getting past
the crank and housing, and poured out the front. If you
would have asked me before hand....I would have said
there is no way possible that that much fuel could come
out the front....and the engine still run....albiet at full throttle.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to David_Moen)
       Post #: 30

RE: Sometimes a deal ait't a deal! - 10/14/2003 9:20:57 PM   
David_Moen



Posts: 1405
Joined: 10/5/2002
From: Salmon ArmBritish Columbia, CANADA
Status: offline 		Egad! I didn't envision that I would be sparking up such a serious debate!

There should have been no issue regarding a "worn" crankcase as the engine in question is brand new! I can feel no play in the bearing. This weekend I put some high-temp RTV silicone under the o-ring on the carb, under the screws that secure the carb, and underneath the back-plate. I also removed the carb barrel and gave it a coating of grease, even though it seems to fit the carb body every bit as closley as the one on my OS 46FX does. I also put some grease on the threads on the HS needle valve to stop air from being pulled through there.

The engine still wants to hold a "high-idle" for an extended period after a full throttle blast, so I'm assuming the only other place that air could get in is around the front. As this engine is a clone of the OS 91FX, I assume a "sealed" bearing of the same dimensions would work.

Does anyone have any idea of what brand/size/model I should get? Is replacing a front bearing relativley easy to do? I imagine that putting a new one in is a matter of baking the engine in the oven at about 250 degrees for a few minutes, while refrigerating the bearing, then dropping the bearing in place. But how do I get the old one out?

Thanks!

(in reply to David_Moen)
       Post #: 31

RE: Sometimes a deal ait't a deal! - 10/14/2003 9:49:02 PM   
Flyboy Dave



Posts: 13518
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: online 		When you get the crank out....you come in from the
back, and bump the front bearing out the front with a
drift, or a dowel rod.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to David_Moen)
       Post #: 32

RE: Sometimes a deal ait't a deal! - 10/15/2003 1:12:16 AM   
Flypaper 2



Posts: 4345
Joined: 3/29/2002
From: Kingston, ON, CANADA
Status: offline 		Tried an experiment with an old Saito 45. Put a rear rotary valve on the backplate. Cut transfer ports around the bottom of the cyl. Made both valves open and close at the same time. So the crankcase was a supercharger. leaked a lot out of the front brg with all that pressure. Bored the front brg housing back further so I could put a seal it. Ran OK but ran hot.

_____________________________

Gord
Dreamed I was a muffler. Woke up exhausted.

(in reply to David_Moen)
       Post #: 33

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