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HelicopterMain Discussion › how to tune my o.s.
10-05-2005 01:16 AM  12 years agoPost 1
fergplane

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state college pa

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i have a raptor 60 with a o.s.70sx-h it has 680mm carbs. it has 4 gl it useing wildcat ys 20/20 can yall help it has a little miss not much the pipe is curtis mp 2 or a good neddle setting to start with thanks

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10-05-2005 04:32 AM  12 years agoPost 2
dkshema

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Cedar Rapids, IA

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thefactoryinitialsettingsare2turnsopenonthemainneedleslotinmixturecontrolscrew
centeredmidrangeneedleoneturnopen.

Now, it's a lot easier to read this post if I use whitespace, punctuation, and full sentences.

The factory setting for the main (high speed needle) is open two full turns. This is the needle closest to the fuel inlet nipple.

The factory setting for the idle mixture (the small screw adjustment between the two needle valves) is to have the screw slot centered and in-line with the vertical axis of the carburetor.

The factory setting for the mid-range needle (the needle farthest away from the fuel inlet nipple, closest to the front of the carb) is one turn open.

These settings ought to give you a good starting point to work with.

Dave

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10-05-2005 05:59 AM  12 years agoPost 3
kc7328

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Kansas City

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So exactly how far is that low end needle turned open then...?

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10-05-2005 10:39 PM  12 years agoPost 4
dkshema

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Cedar Rapids, IA

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If you take the time to understand how that carburetor works, you'll realize that the "low" end needle doesn't affect the mixture by going "in" or "out", rather, it affects the position of the needle through the action of a cam.

Turning that little screw in the middle of the two "big" needles moves the little brass plate left or right (the screw is not a screw, but a cam). The lower end of the little brass plate is attached to the actual mixture control device, and rotates a slotted opening back and forth inside the carb.

The bottom line is that the factory position for that little screw is in the middle of its adjustment range -- the slot in the screw is parallel to the axis of the carb. You only turn that screw about + or - 30 degrees total from the factory setting -- no more.

Dave

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10-07-2005 01:48 AM  12 years agoPost 5
fergplane

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state college pa

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So it dose not work like the o.s. 32 low end ? Can i see the brass move ?Thanks i need all the help i can get.

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10-07-2005 03:11 AM  12 years agoPost 6
Secret Squirrel

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New Zealander living​in Melbourne,​Australia

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Check out the engine tunign article on my site here at http://www.littlerotors.com/article...40103/index.asp

-------------
Simon Lockington

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10-07-2005 04:15 AM  12 years agoPost 7
dkshema

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Cedar Rapids, IA

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Let's see...the 70 has a three needle carb. One for high, one for low, and one for mid range.

The 32 has a two needle carb, one for high, and a recessed screw adjustment for the low end.

I think the answer is ... ... no, the 70 doesn't work the same as the 32.

And yes, if you take a small screwdriver and turn the low speed adjustment screw on the 70, you'll see that little brass plate that surrounds the screw move left and right.

I'm sure you have a manual for your 70, but if you don't, go here:

http://www.os-engines.co.jp/english.../70sz-hring.pdf

download it, and start reading at page 14, and don't stop until you get to page 20. Everything you need to know about tuning your carb is right there.

Dave

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10-07-2005 04:30 AM  12 years agoPost 8
fergplane

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state college pa

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thanks ill do that . maybe it will help

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10-07-2005 11:14 PM  12 years agoPost 9
fergplane

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state college pa

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Secret Squirrel i did it like you said. it works like a champ. thanks

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10-08-2005 02:39 AM  12 years agoPost 10
Secret Squirrel

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New Zealander living​in Melbourne,​Australia

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Excellent, I'm glad it helped.

Si

-------------
Simon Lockington

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