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Engine basics => Engine set up tips => Topic started by: Fred Quedenfeld jr on August 25, 2019, 07:19:54 AM
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Since you can no longer get the OS needle assembly and the tigre or PA are too big
What should you use? where do you purchase?
Does the OS nipple in the venturi with a remote needle work or just another headache
DO NOT ANSWER WHAT YOU "THINK"
I want to see proof that what you are typing "WORKS"
Fred Quedenfeld
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Contact Bob Brooks from Ebay aka Shtterman Part# 54020 direct Enya replacement for OS .20-.46
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Some will say not to, but you can drill the case and use a PA NVA from Randy Smith or a DoubleStar NVA from Tom Dixon. Many people do and they work just fine.
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like mike says.after drilling the case out u can turn down the center of the sprybar to the original size
OH and yes I have done it. works fine H^^
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If you are forced to use a larger needle valve assembly, just increase the venturi a few thousandth to compensate. You just need to match the choke area and the engine will not care. It had no idea what kind of NVA that is being used. This is not what I THINK, it is what has been done and discussed on the forums countless times, and is what I consider basic engine 101.
Type at you later,
Dan McEntee
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If you are forced to use a larger needle valve assembly, just increase the venturi a few thousandth to compensate. You just need to match the choke area and the engine will not care. It had no idea what kind of NVA that is being used. This is not what I THINK, it is what has been done and discussed on the forums countless times, and is what I consider basic engine 101.
It needs a lot more than a few thousands, it needs .273 or or so (.016, 16 thousands) with an ST spraybar (not recommended) and a lot more with a PA and more still with the RO-Jett. I would measure the RO-Jett spraybar and figure out what the necessary diameter venturi bore should be, except that, apparently, someone has "liberated" my box of replacement RO-Jett spraybar and venturi parts.
If you just enlarge it "a few thousandths", you will have to run a prop with more pitch (since it won't rev up enough for the correct prop, which is an APC 9-4) and thus start giving up the advantage it has over old crock engines like the Fox 35, and your Skyray/Flight Streak will start flying like a "trainer" again.
However, there is no need to keep destroying crankcases to fit erzatz parts, a correct part is available here:
https://www.ebay.com/itm/OS-FP-LA-20-46-NEEDLE-VALVE-ASSY-DIRECT-REPLACEMENT-NIP/293139719059?hash=item44407d2393:g:0-8AAOSwJRFcolWt
Which then permits you to run the stock venturi (.257") like you should.
The rear-needle setup from the OS20FP-S RN will work just fine, as well as the front needle, if you have those parts. It also works fine on the 25LA, if you have broken the backplate (but not cracked the sealing face), or if you have replaced the backplate with an aluminum aftermarket part. (harmless but unnecessary).
There is no significant question about how to run it - it's been documented endlessly since public access to the internet has been available.
I would be *extremely surprised* if anyone has run these engines in more different configurations than I have, *stock straight out of the box* is the best way.
Brett
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100s of people have used the PA NVAs in the OS 20 25 35 40 46,
The PS Bar is the same size as the Super Tiger, and the same size as the older OS bars. .157
The FP and LA series was when OS decided to just make only the 20 size bar and use it in all of their engines
A good fit since the OS is much smaller diameter, it to use the .255 with the OS bar, and .280 with the PA or ST NVAs
DO NOT try to turn the st or PA bar down on a lathe, it is much easier to resize the venturi, and you will not risk the bar breaking if you get it a little too tight.
This is no bid deal and its easy to do, People much prefer the PA assemblies to the OS or ST
or use the stock setup, but try not to mix setups that do not match
and drilling the case hole and venturi side holes to .157 does NOT ruin the case, it just makes them the same size as the OLDER OS engines Like the 30 35 S 40 45 FSR Max 40 H etc
Randy
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Needle adjustment is much finer using a Super Tiger type needle valve.
Sent from my iPhone using Tapatalk
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Needle adjustment is much finer using a Super Tiger type needle valve.
Sent from my iPhone using Tapatalk
And it is even finer using a PA assembly
Randy