Two needle carb for OS140

[AtwoodDon at aol.com]

Colin, there are 2 mixture control carbs avail today (that I know  of).  
First, the OS 70B is the mixture ctl carb made for the OS140.   It is very hard to 
locate since OS stopped production of them shortly after they  began selling 
their EFI versions of the 140 (and 160).  Sometimes you can  find one on RC 
Universe and you could also try Cyber Heli in Hong Kong.  I  hear some have been 
able to get one there.
 
The second alternative is to retro fit the Webra mixture ctl carb (standard  
on the Webra 160) and I believe you can get them thru Central Hobbies.  You  
need to have someone turn the neck of the carb down to fit into the OS but  
that is a very simple/quick thing to have done or do if you have access to a  
metal lathe.  I suppose it could be done with a drill press and file if you  are 
patient enough but is only about 5 minutes work on a metal lathe. And I bet  
that would void the 'warranty' too   ;-))))
 
Several of us have been successful in using the Webra carb on the OS tho I  
will say it is more sensitive to setup than the OS.  I think the reason for  
this is the OS pump puts out a little more pressure than the Webra pump and that 
 creates the sensitivity using the Webra carb.  Don't get me wrong, the  
Webra carb will work on the OS, it is just more sensitive.  I have also  heard 
(not done). 
 
I have also heard there have been some minor issues with the small o-ring  in 
the mixture ctl barrel binding with the Webra carb and that has been fixed  
with going to a different o-ring or machining the slot for the o-ring slightly  
deeper to alleviate the binding.  Others on the this group may have direct  
experience with that.
 
When adjusted properly, the mixture ctl carb setup is great, very smooth,  
linear response with no mid range gurgle and the transition to idle is quicker  
and settles into a low idle very nicely with little delay.
 
Don Atwood
 
 In a message dated 9/16/2005 7:45:39 P.M. Pacific Daylight Time,  
cchariandy at yahoo.ca writes:

Does anyone know who sells the mixture control carb for OS140rx?
 
Colin Chariandy.



 
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