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OS Four Stroke needle settings

Old 01-14-2007, 06:42 PM
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moto-x
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Default OS Four Stroke needle settings

Hi all, I hope someone could enlighten me on some not so average needle settings. I have 2 OS Fs 90s. One the high speed needle has to be set completely closed for it to run at peak rpm. If you open it at all it just slobbers. I have only run this motor on test stand because I am not confident with it in the air. The other 90 runs best at 2 1/8th turn out. I also have a 91 surpass that has to be closed off on the high speed to run at peak. The needles look fine in the two problem motors But I thought I had read somewhere that the needle is two piece and that the actual needle could be pushed back inside the adjusting portion of the needle. any help would be appreciated.
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Old 01-14-2007, 07:35 PM
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Default RE: OS Four Stroke needle settings

have you owened these since new?what you read may be true .most os needles are 2 piece but are silver soldered or are a tight press fit.have you compares the lengths of the needles of the poor runners to the good one?are they shorter?could be they are not the right needle for that engine.years ago I had a hp 61 that the solder let go on and had to be reser and resoldered.the only other thing i can think of is that the low speed needle is screwed to far in and is preventing the high speed from fully closing,screw the high speed in all the way,then back out the low speed needle a turn or two and see if you can turn the high speed in more.
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Old 01-14-2007, 07:47 PM
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moto-x
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Default RE: OS Four Stroke needle settings

aerowoof, I backed out the low speed needle. the high speed would still not go in anymore. As for comparing needle length, the one that runs correct is not here at this time. It is at a freind of mines. I will get it back though and measure them both.
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Old 01-14-2007, 07:53 PM
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Default RE: OS Four Stroke needle settings

No, I have not owned them since new and your right, they could be the wrong needles. Oh and that is friend of mine. I can spell, it's just a little too dark in here.
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Old 01-15-2007, 12:17 PM
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Default RE: OS Four Stroke needle settings

If an O.S. needle has to go in very far or be closed or the engine's too rich, it's likely that the needle seat in the carburetor body has been damaged. Usually, the high-speed needle on most O.S. non-pumped engines will be about 1-1/2 turns out from closed when the engine's running just rich of peak RPM. That number of turns will vary a bit, depending upon how well the engine's getting fuel. If you have to turn the needle in a lot more, then you'll likely need a new carburetor body because the needle seat's been damaged at some point in time.
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Old 01-15-2007, 09:25 PM
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Default RE: OS Four Stroke needle settings

buy a different motor , or get one from a real... good.....buddy.....
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Old 01-16-2007, 07:04 PM
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Default RE: OS Four Stroke needle settings

Buddy, Whats that. I don't think I have any.
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Old 01-17-2007, 10:24 AM
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Default RE: OS Four Stroke needle settings

I had this problem once on an old OS 90 (Pre-Surpass) At the time, I worked in a machine shop so I just turned the collar down so I could get another revolution or two on the needle - worked like a charm!
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Old 01-17-2007, 01:36 PM
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Default RE: OS Four Stroke needle settings

Screw your slow speed adjustment out until it is flush with the surface. Screw the highspeed in all the way and then screw it out 1 and 1/2 turns. Fine tune for max from there.
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Old 01-27-2007, 08:51 AM
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Default RE: OS Four Stroke needle settings

Well,here is what I did. Opened the needle valve a couple of turns and just put a remote needle valve inline with carb to tank connection. Worked like a champ.
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