OS mixture question

Sun Sep 18 16:45:18 AKDT 2005

Bob,

I saved the below messages some time ago and am now getting around to 
reading it again.  I am at the header and pipe installation right now and 
find your write-up below useful.  Thanks for sharing it with us.

Bob Harden

----- Original Message ----- 
From: <rcaerobob at cox.net>
To: <discussion at nsrca.org>
Sent: Tuesday, April 19, 2005 10:27 AM
Subject: Re: RE: OS mixture question

> This is good info, no doubt!!!
> Just a thought - many folks want a "starting point" for pipe length. 
> Experimenting with different props/pipes and motors - all things being 
> about equal (I know they're not, really, but it's okay), I've found the 17 
> x 12 APC or similar load starting point to be about 23.75 -24" plug to 
> reflector, following headers curves, and the "wave" length.
>
> This measurement will get a person who's in a hurry in a flyable condition 
> pretty fast, with minimal additional tweaking.
>
> Of course, YMMV, depending on a lot of things, but the most frequently 
> asked question I get by the newbie two-stroke convert (or a former 2 
> stroker who has RE-converted)is "what's a good starting point for 1.40 - 
> 1.70's in today's planes?"
>
> Hope this is helpful to someone.
>
> Bob P.
>>
>> From: "richard.lewis" <richard.lewis at idmcontrols.com>
>> Date: 2005/04/19 Tue AM 11:08:47 EDT
>> To: <discussion at nsrca.org>
>> Subject: RE: OS mixture question
>>
>> Thanks again Wayne...:)  Very well spoken, clear, and concise 2-stroke
>> tuning methodology.
>>
>> Richard
>>
>>   _____
>>
>> From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] 
>> On
>> Behalf Of Wayne Galligan
>> Sent: Tuesday, April 19, 2005 9:12 AM
>> To: discussion at nsrca.org
>> Subject: Re: OS mixture question
>>
>>
>> I helped a guy with the a similar issue this weekend on his Mintor.   Way
>> too lean on the bottom end. His would pop on acceleration or die coming 
>> out
>> of the outside loop.
>>
>> For the OS 1.40 RX Try this:
>> Use an OS "F" plug.
>> 15% nitro
>> I have not had to adjust the pump on any of the OS's I have set up to 
>> date.
>>
>> Set the top end till it peaks in rpm(use a tach if you have one) and back
>> off one click to the rich side.
>> Bring it down to an idle and try  to set the idle to about 18-1900 rpm.
>>
>> Let the engine idle for at least 20-30 seconds and do not touch the
>> throttle.
>>    1.  if it speeds up or surges at any time during this time the bottom 
>> end
>> is lean.
>>    2.  if the engine gradually slows down and dies...its rich.
>>
>> Advance the throttle with medium speed and observe:
>>    1.  if it burbles and picks up speed or burbles and dies bottom end is
>> too rich.
>>    2.  if it falls flat or hesitates then accelerates or dies it is lean
>>
>> This may take several tries to get but once its set then its just minor 
>> top
>> end adjustments depending on weather conditions.
>>
>> Changing pipe lengths will also effect the low end transition.   A longer
>> pipe setting will allow you to set the bottom end a little richer and 
>> give
>> better downline braking.
>> I find that running the bottom end as rich as possible with out it 
>> loading
>> up gives the best downline deceleration.
>>
>> Setting your pipe is a whole other story.   My best method is on a test
>> stand.   Set the pipe long and run engine, tach the top end at peak rpm.
>> Shorten the coupler or pipe about 1/4" at a time and observe the peak 
>> rpm.
>> It will increase with each shortening of the pipe.
>> Once it peaks in rpm or no longer increases or drops in rpm this is the 
>> top
>> tuning spot for your engine and pipe for max rpm(not really the desired
>> tuning).
>> At this point back the pipe off about 3/8 to 1/2".   This will give you a
>> good starting point.  I usually lengthen the pipe if I go to a higher 
>> loaded
>> prop or
>> shorten it with a lighter loaded prop.
>>
>> The OS 1.40 is a very predictable engine.   If it starts to load up and
>> stall in the midrange for no apparent reason or drops rpms
>> after the glow plug is removed first check the plug . If it continues to 
>> do
>> the same thing then the bearing is probably on its way out.
>> Replace the bearing with a sealed bearing or a stainless steel bearing 
>> that
>> goes in the EFI version.   I have about 200 flights on one
>> of my OS's that has the sealed std steel bearing from Bearings Limited in 
>> it
>> and it is still going strong.   Another way to check the bearing is move 
>> the
>> prop by the tips
>> perpendicular to the engine and if you can feel end play the bearing is
>> getting loose.
>>
>> Wayne Galligan
>>
>> ----- Original Message ----- 
>> From: Kurt  <mailto:kurt at bozarthhomes.com> Bozarth
>> To: discussion at nsrca.org
>> Sent: Monday, April 18, 2005 7:22 PM
>> Subject: OS mixture question
>>
>>
>>
>> OS 140 RX (non-EFI) question:
>>
>>
>>
>> When I advance the throttle, the rpms remain at idle for approx. one 
>> second,
>> "pop" and then advance to full throttle rpms  I am not quite sure if this
>> "pop" and hesitation is a result of having too lean of an idle mixture or
>> too rich.  This is an older motor released back when Hobby Services 
>> offered
>> a free needle valve assembly replacement to correct for mid-range 
>> richness
>> issues.  I do not know if this was done or not - something I will check 
>> for
>> tonight.  I have never adjusted the pump setting.  Let me know your
>> thoughts.  Thank you.
>>
>>
>>
>> Kurt Bozarth
>>
>>
>>
>
> Bob Pastorello, El Reno, OK, USA
> rcaerobob at cox.net
> www.rcaerobats.net
>
> =================================================
> To access the email archives for this list, go to
> http://lists.f3a.us/pipermail/nsrca-discussion/
> To be removed from this list, go to http://www.nsrca.org/discussionA.htm
> and follow the instructions.
>
> List members email returned for mailbox full will be removed from the 
> list.
> 

=================================================
If you want your reply email to go to the list, you must Cc: the list!

To access the email archives for this list, go to
http://lists.f3a.us/pipermail/nsrca-discussion/
To be removed from this list, go to http://www.nsrca.org/discussionA.htm
and follow the instructions.

List members email returned for mailbox full will be removed from the list.